There is no real consensus on the number of cells in the human body. Estimates put the number between ten trillion and one hundred trillion. A trillion is a million million—it’s a word that crops up when we talk about the size of our national debt! The number of cells depends on the size of the person: bigger person, more cells. Also, the number of cells in our body keeps changing as old cells die and new ones form.
Cells are so small that most can only be seen through a microscope. Every cell is made from an already existing cell. Each cell in the body behaves like a little factory and has two major components, the cytoplasm and the nucleus. The cytoplasm contains the structures that consume and transform energy and perform many of the cell’s specialized functions, including storing and transporting cellular materials, breaking down waste, and producing and processing proteins. The nucleus is the control center and contains the genetic information that allows cells to reproduce. The mitochondrion (plural mitochondria) in the cell is the factory where food and oxygen combine to make energy. Human cells and other animal cells have a membrane that holds the contents together. This membrane is thin, allowing nutrients to pass in and waste products to pass out. Food is the energy the cell needs. Each cell needs oxygen to burn (metabolize) the nutrients released from food.
The body has some cells that do not experience cell division. And red blood cells and outer skin cells have cytoplasm but do not have a nucleus.
In the cell, the process is called respiration. Oxygen breaks down the food into small pieces. The oxidizing of the food molecules is turned into carbon dioxide and water. Water makes up about two-thirds of the weight of the cell. The energy released is used for all the activities of the cell. The cell membrane has receptors that allow the cell to identify surrounding cells. Different kinds of cells release different chemicals, each of which causes certain other types of nearby cells to react in certain ways. Within each of these different cells are found twenty different types of organelles, or structures.
Slightly over two hundred different kinds of cells make up the human body. The shape and size of each type of cell is determined by its function. Muscle cells come in many different forms and have many different functions. Blood cells are unattached and move freely through the bloodstream. Skin cells divide and reproduce quickly. Some cells in the pancreas produce insulin, others produce pancreatic juice for digestion. Mucus is produced in cells in the lining of the lung. Our lungs also contain alveolar cells that are responsible for taking in gas from the blood. The cells that line the intestine have extended cell membranes to increase the surface area, helping them absorb more food. Cells in the heart have a large number of mitochondria to help them process a lot of energy, because they have to work very hard.
Nerve cells generate and conduct electrical impulses; for the most part, they do not divide. Each nerve cell has a specific place in our nervous system. Nerve cells outside of the brain are very long and have the task of passing signals between the brain and the rest of the body, allowing us to move our muscles and sense the world around us. The rest of our nerve cells—about one hundred billion of our body’s cells—are brain cells.
Brain cells are the most important cells in our bodies. It is our brain that defines who we are. Brain cells in children under five do have the ability to reproduce, to some extent. However, we are naturally losing brain cells all the time. The best estimate of normal brain cell loss is put at nine thousand per day. That may seem like a large number, but remember that the brain has 100 billion cells, so a nine-thousand-cell loss per day is not that great. Inhalants, such as glue, gasoline, and paint thinner, cause brain cell loss at thirty times the normal rate. Excessive alcohol use is a big contributor to brain cell damage.
Cells that all do the same job make up tissue, such as bone, skin, or muscle. Groups of different types of cells make up the organs of the body. Different organs grouped together form a system, such as the digestive system or the circulatory system. All the systems working together make up a healthy human body.
Cells live, of course, but cells also die. Liver cells last about a year and half. Red blood cells live for 120 days. Skin cells are good for 30 days. White blood cells survive for thirteen days. And it turns out that the great majority of cells in the human body are bacterial cells, and most are beneficial. It is hard to believe that the average adult loses close to 100 million cells every minute. The good news is that the body, through cell division, is replacing those lost 100 million cells every minute. And in any case, even 100 million cells is only a small fraction of the trillions of cells that make up our bodies.
Babies get sick more often than older children or adults because their immune systems are not fully developed and functioning at full capacity. The common cold, which is an infection of the respiratory system caused by a virus, is the most frequent malady. Doctors say that normal, healthy babies get up to about seven colds before they reach their first birthday. Another common affliction is the flu, caused by a different family of viruses, which bring on high fever, chills, fatigue, and sometimes digestive symptoms like vomiting and diarrhea, in addition to the respiratory symptoms of a cold.
Another reason babies get sick so often is that they are frequently around other children, often siblings, and this exposes them to viruses and bacteria in school and daycare. Children in schools and daycare get more colds, runny noses, and ear infections than children cared for at home. However, their earlier exposure to these diseases also leads them to develop immunity earlier.
Babies are also curious about the wide, wonderful world they are born into. So they will stick anything and everything into their mouth as a means of exploring that world. You can imagine the enormous amount of germs that ride along.
Furthermore, babies have not developed the immunity to the many different viruses that cause colds, because they haven’t had time to acquire the antibodies to fight off viruses. Babies do have some of their mothers’ antibodies when they are born, which were transmitted through the placenta during pregnancy. This kind of immunity isn’t permanent, but breastfeeding can extend it, because many of the mother’s antibodies are present in her milk. This is why breast-fed babies tend to have fewer colds and flu symptoms than bottle-fed babies. Babies, like other people, also develop their own antibodies in response to germs they are exposed to; in fact, it’s a mistake to try to eliminate all pathogens from a baby’s environment.
Winter is the toughest time for babies, because it is the season when colds spread nationwide. Also, in winter people spend more time indoors, where viruses are more likely to spread from one person to another. The less humid air of indoor heating dries nasal passages, which allows viruses to thrive.
All people, both adults and children, are susceptible to bacterial and viral infections. Bacterial infections include meningitis, cholera, bubonic plague, tuberculosis, diphtheria, and anthrax. Vaccines for these dreaded ailments were developed decades ago. But when the very young and very old get sick, it is most often from viruses. A prime example is the common cold.
There is no cure for the common cold, because many different viruses cause colds and even if a medicine is developed for one of them, people would still catch colds from other viruses. Many people who have colds, or whose children have colds, ask their doctors for antibiotics, because they don’t understand that these drugs don’t work against viruses. But there are medicines that can relieve the symptoms of colds and flu so babies can get better sooner and not suffer as much. Recent research has developed medicines against some viruses; for example, the vaccine that helps prevent the flu can also treat it if given soon enough after a person develops symptoms.
Elderly people get sick more often because their immune systems are weakened or breaking down. They also tend to have existing conditions that make them more vulnerable. Some have heart disease, kidney problems, asthma, diabetes, and a whole host of illnesses that no one looks forward to. Many of these diseases, as well as their treatments, suppress the immune system.
That’s why the Centers for Disease Control and Prevention (CDC) advises that children under five years of age and people over sixty-five years of age have flu shots when each new strain begins to spread. Most people who contracted the H1N1 swine flu virus in 2009 came down with a mild illness, but the fatality rate was high. According to the World Health Organization (WHO), 284,500 died from the H1N1 virus, the majority being from Africa and Southeast Asia.
A birthmark is a colored spot on or just under the skin. Most birthmarks show up when a baby is born. Some are noticed shortly after the baby is born. Some birthmarks fade away as the child grows up, but some stay and get bigger, thicker, and darker.
Nearly all birthmarks are harmless and painless. They can be almost any size, shape, or color.
Birthmarks have two primary causes: blood vessels that bunch together or do not grow normally and extra pigment-producing cells, or melanocytes, in the skin. Doctors don’t know what’s responsible for these two causes, but many think there is a genetic component involved.
The most common birthmark is the port-wine stain. The stain is usually pink-red at birth and tends to become red or purple as a person ages. Port-wine stains, caused by blood vessels that do not grow normally, can have various sizes and shapes. Port-wine stains most often show up on the face, back, or chest. The strawberry birthmark is another that is found on newborns. It is also caused by a clumping of blood vessels that do not grow normally. Mongolian spots are benign congenital birthmarks found mostly on East Asians. Originating on the lower back, these bluish spots disappear by the time the child reaches age five. A salmon patch is a very common birthmark, occurring on 75 percent of newborns. It is caused by dilation of tiny blood vessels. Most salmon patches disappear by age one or two. Stork marks appear on the back of the neck, middle of the forehead, or upper eyelids. They vanish by the time the child is two years old.
The downside of birthmarks is that kids have to live with the teasing, ribbing, and cruel remarks of classmates. Some kids can go through a miserable childhood enduring the slings and arrows of their peers. But there is some good news. Makeup creams can hide many birthmarks on the face and neck or make them less noticeable. Others can be removed by surgery or lightened with a laser, but these treatments can be painful. Since most birthmarks are harmless, most are not treated.
Blood is red because hemoglobin, a protein in red blood cells that binds oxygen and carbon dioxide, contains chemical compounds called hemes, and a heme is a blood pigment that contains iron, which is reddish in color. There are about thirty-five trillion red blood cells—tiny, round, flat disks—circulating in our blood at any one time—that’s thirty-five followed by twelve zeroes. And each red blood cell typically has more than 250 million hemoglobin molecules, each with four heme groups!
Blood is pumped by the heart and circulated around the body through blood vessels. Blood is bright red when the hemoglobin picks up oxygen in the lungs. The red blood cells carry the oxygen, bound to their hemoglobin, to the rest of the body through arteries and capillaries. Carbon dioxide from the body’s cells returns to the heart through capillaries and veins. The darker venous blood carries the carbon dioxide from the tissues to the lungs, which expel them.
The blood coursing through our body’s plumbing of arteries, veins, and capillaries contains many different materials and cells. Plasma, the liquid part of blood, is a light yellow color, denser than water, and carries proteins, antibodies to fight diseases, and fibrinogen, which helps the blood clot. Plasma also has carbohydrates, fats, and salts. Young red blood cells mature in the marrow of the bone. Red blood cells have a life expectancy of about four months. Then they are broken up in the spleen and replaced by new blood cells. New cells are constantly replacing old cells. Our blood also contains several types of white blood cells. When a germ infects the body, some white blood cells race to the scene and produce protective antibodies that overpower the germs, while other white blood cells surround and devour them.
The average adult has between eight and twelve pints, or four to six quarts of blood. If a person loses a significant portion of their blood supply, they go into shock and die. This can be prevented by transfusing blood from another person with a matching blood type (see question 8). The first blood transfusion on record took place in 1665. Richard Lower of Oxford, England, took blood from one dog and put it in another dog. The first known human-to-human blood transfusion took place in 1795 in Philadelphia.
Some short answers: lots of junk foods have loads of sugar. Many junk food items are brightly colored, which attracts our (especially children’s) attention. People like finger foods, such as burgers, hot dogs, and fries. Advertisers target children, making junk food more attractive than is healthy from a young age. Deep-fried foods are tastier than bland foods, and children and adults develop a taste for such foods. Fatty foods cause the brain to release oxytocin, a powerful hormone with a calming, antistress, and relaxing influence, said to be the opposite of adrenaline, into the blood stream; hence the term “comfort foods.”
We may even be genetically programmed to eat too much. For thousands of years, food was very scarce. Food, along with salt, carbs, and fat, was hard to get, and the more you got, the better. All of these things are necessary nutrients in the human diet, and when their availability was limited, you could never get too much. People also had to hunt down animals or gather plants for their food, and that took a lot of calories. It’s different these days. We have food at every turn—lots of those fast-food places and grocery stores with carry-out food.
But that ingrained “caveman mentality” says that we can’t ever get too much to eat. So craving for “unhealthy” food may actually be our body’s attempt to stay healthy.
Food manufacturers put color additives in their foods. Bright, vibrant, saturated colors look more appealing to consumers. A bright red apple is more appealing than a dull red or green apple. A key to survival in olden times was the ability to recognize foods that contained usable energy or nutrition. People needed to be able to recognize foods that contained many calories, would support healthy brain function, harbored healing medicines, and boosted the immune system. Many of those natural foods often appeared in bright colors, such as apples, oranges, bananas, carrots, and berries. Color was a reliable indicator of a healthful food. Indeed, when apples, bananas, or berries spoil, they lose their bright colors. So food-manufacturing companies are exploiting what was once a well-based notion that colorful foods are healthy foods!
Additives make foods taste better, look better, and last longer on the shelf. Experts agree that all those additives can’t be good for us. Some additives come from coal tar and petrochemicals. Our bodies are not made to ingest crude oil. Some additives have been shown to be safe, but many have not even been tested. There is growing suspicion that all those additives are responsible in part for a rise in child obesity, attention deficit hyperactivity disorder (ADHD), and questionable behavior patterns. Some food dyes, such as Blue #2, Yellow #5, and Red #40, have been linked to cancer and ADHD.
At the same time, some foods have their nutrients subtracted. White flour starts out as whole wheat flour, but the manufacturers strip out its fiber, along with many nutrients. Then they “enrich” it by adding back some nutrients, but it’s not the same as the original whole grain.
Another side effect of our taste buds’ being attracted to unhealthy foods is the huge increase in type 2 diabetes, from a double whammy of eating too much and eating the wrong kinds of food. This is a type of diabetes that used to appear after adulthood—in fact, it’s often called “adult-onset diabetes.” But lately, more and more cases begin during childhood and adolescence, and this has been linked to the increase in childhood obesity. Anything made with a high sugar content and/or white flour spells trouble for the diabetic. That means cookies, cake, candy, soda pop, ice cream, and pastries. These foods are loaded with fat and salt that contribute to high blood pressure and heart disease. Most of us like to eat these delicious foods. So experts say it goes back to Aristotle’s advice for a happy life: the Golden Mean—moderation in everything.
The definition of a nightmare is a really bad and distressing dream that causes a strong feeling of fear. A nightmare quickens a person’s pulse and makes them sweat. Sometimes, the sleeper feels so frightened and threatened that they wake up. Sleep experts estimate that 30 to 50 percent of all kids have some nightmares, but luckily, they usually grow out of them. The most common nightmare I had as a kid was that of being chased, but I can’t recall why I was being pursued.
Nightmares can be fairly long and complex. The person senses a threat to safety or life. As the threat increases, so does the sense of fear. A person tends to wake up just as the threat or danger reaches its peak.
About 3 percent of young adults have frequent nightmares. One in two adults have a nightmare on occasion. An estimated 2 to 8 percent of adults are plagued with frequent nightmares. Stress, depression, and anxiety are commonly associated with nightmares in adults. A major life-changing event can cause them, such as loss of a job, financial worries, marital difficulties, death of a spouse, or moving to another house. Alcohol abuse or abrupt withdrawal from alcohol can also lead to nightmares.
Nightmares occur during the rapid eye movement (REM) phase of sleep. REM is about two hours of a normal night’s sleep, but other phases of sleep break that time up into four or five episodes. REM phases become progressively longer as the night progresses, and so you may find you experience nightmares most often in the early-morning hours of REM sleep. One can have four to five episodes of REM but still usually have nightmares in the later stages of sleep
Traumatic experiences, such as surgery, brain injury, war, and combat, with their attendant post-traumatic stress disorder (PTSD), can bring on nightmares. Stress is thought to be the most common source of nightmares, so relaxation techniques, such as yoga and meditation, have proven helpful. And eating right before going to bed can increase the frequency of nightmares, since eating increases metabolism and brain activity.
There is no diagnostic test for nightmares. Persistent disorders surface when people report them to a family doctor or a psychiatrist.
Braces have two results: They make your teeth straight, and they make your parents get a second job to pay for them!
Actually, straight teeth help a person effectively bite, chew, and speak. Teeth that are properly aligned tend to look better and work better. Straight teeth can also prevent decay by giving plaque fewer places to hide. That nasty plaque can lead to gingivitis or more serious periodontal (gum) disease. Protruding front teeth have a good chance of being broken or fractured in an accident. Crooked teeth can cause abnormal wear on tooth surfaces, misalignment of jaw joints, neck and facial pain, and even headaches.
An attractive smile is a positive side effect of having straight teeth, bolstering self-esteem and self-confidence. Good teeth can be a social and career booster.
So how do braces work? They put pressure against the teeth, which makes them gradually move over a period of time. The pressure comes from an “arch wire” attached to the braces that runs on the outside of the teeth. The top teeth and the bottom teeth form separate arches. The arch wire is springy, and when attached to the braces on the teeth, it becomes deformed or bent along the path of the uneven teeth, and so it exerts a gentle force on the teeth to gradually move them to their desired position. Sometimes the braces are put on the inside of the teeth, where they are invisible. But that can cause problems, such as speech impediments and irritation of the tongue.
Older braces had the arch wire connected to large metal bands cemented around each tooth. Today’s braces have the arch wire attached to tiny brackets that are cemented to the front of the teeth, with a slot on the outside to hold the wire. In both kinds, as the teeth get closer to the desired positions, the arch wire needs adjustment from time to time to apply continuous pressure to move them over the next interval.
Newer arch wires are made from Nitinol (nickel titanium naval ordnance lab) wire, a space-age metal alloy that NASA uses to deploy satellite antennas that are folded up during launch.
The Naval Ordnance Lab, located in the Maryland countryside, established in the early 1920s, carried out important work in countering Germany’s magnetically activated mines dropped by aircraft into Allied shipping lanes in WWII. After WWII, the Naval Ordnance Lab did basic research on metals, explosives, wind tunnels, underwater weapons, and radiation detection.
At room temperature, the Nitinol is very flexible and will hold a deformed configuration, but when heated, the nickel titanium (Ni-Ti) wires return to their original shape. So, in the heat of a person’s mouth, the alloy wire that has been bent along the uneven teeth continually applies pressure to the teeth as it returns to its former contour.
After applying an etching material to each tooth, which prepares the enamel for a bonding agent that will hold each bracket to the tooth, the orthodontist rinses the etch and applies a sealant chemical, then applies the brackets to the tooth surfaces. The bonding material does not harden, or set, until the orthodontist shines ultraviolet light on it; this allows time for any last-minute adjustments on the placement of the bracket before attachment of the arch wire to the brackets.
The first arch wire is round, thin, and flexible. In subsequent visits, the orthodontist uses rectangular, larger-diameter wires. The wire slot of the bracket is rectangular, so a rectangular wire fits more snugly into the bracket and exerts a greater force. Braces are generally left on for a tad less than two years. To keep the teeth straight after removal of the braces, people wear a retainer. The retainer holds the teeth in their correct positions while bone fills in around them. A retainer is worn for three to six months. The orthodontist may recommend wearing the retainer only at night, especially during those later months.
About 4.5 million people in the United States wear braces. Most are teens, but 20 percent are older adults. Some couldn’t afford braces when they were younger; some decided they wanted straighter teeth or a better smile, or had a dentist who recommended braces.
That is not exactly the case; it depends on which blood type the recipient has. A blood type, or group, is a classification of blood based on whether or not inherited antigens reside on the surface of red blood cells. Antigens are foreign substances that induce an immune response and interact with specific antibodies in our immune systems.
In 1900, Austrian doctor Karl Landsteiner found a basis for classifying human blood into four groups. He discovered that red blood cells could carry two different antigens, which he termed A and B. Each of us has two ABO blood-type alleles (different forms of the same gene), because we each inherit one blood-type allele from our biological mother and one from our biological father. The presence or absence of the A and B antigens makes for four possible blood types: A, B, AB, and O. A person with type A blood has red blood cells that carry only antigen A. One with type B blood has red blood cells that carry only antigen B. An individual with AB blood has both antigens, and one with type O has neither. There is another antigen on red blood cells, called the Rh factor. This antigen is named Rh for the Rhesus monkeys the experiments that discovered it were done on. People who have the Rh antigen are said to be Rh positive. Those who have the Rh antigen missing are called Rh negative. Blood banks group people on the basis of their ABO and Rh factors into categories like AB negative or O positive.
A test called an antibody screen, performed on patients who may require red blood cell transfusions, detects most red blood cell antibodies.
When a person receives a transfusion of blood, their body recognizes the received blood as either “foreign” or “familiar.” A person whose blood type is O will reject all other blood types, because their body does not recognize the A and B antigens. This sets off an immune response in which antibodies attack the new blood, either destroying its red cells or causing it to clot, which, unfortunately, often leads to the death of the individual. However, when a person with the A or B blood type needs blood, they can receive their own blood type or type O, and a person with type AB blood, known as the universal recipient, can receive any of the four types.
Blood type varies by ethnicity. Type O blood is carried by 45 percent of the population, 35 percent have Type A, 15 percent have Type B, and 5 percent carry Type AB. Type O is called the universal donor, because it is the only blood type that can be transfused to patients with all other blood types in the ABO group. So blood banks like to have a lot of type O donors. About half of all the blood ordered by hospitals is type O. Rh-negative blood is like the type O of the Rh blood group system: people with either Rh-positive or Rh-negative can safely receive it, while it is not safe for people with Rh-negative blood to have Rh-positive blood transfused.
Oh, I know what you mean. I just read my 401(k) statement! Actually, tears are good. Tears clean and lubricate the eyes. While most animals have a system to keep their eyes moist, we humans are the only mammals that cry emotional tears, which are triggered by a part of the brain that’s responsible for feelings of sadness. This melancholy then sends signals to the endocrine system to release hormones around our eyes that cause tears.
Strong emotions can come from being very happy or very sad, or from enduring pain or being under a lot of stress. These emotions can result from getting an F on your report card or receiving your tax bill in the mail, or from lost love, a tear-jerker movie, or overwhelming joy. In addition to emotional tears, there are tears caused by irritation. If we get something in our eyes, such as a piece of dust or debris, producing tears helps wash it out of the eye.
Vision is one of God’s greatest gifts to us. So it is in our interest to have a basic understanding of vision, how the eye works, and how to take care of these wonderful gifts.
The tear glands, or lacrimal (also spelled lachrymal) glands, are located under the upper eyelid. Tears flow through tiny ducts that secrete tears onto the eyeball in a process called lacrimation (or lachrymation). The tears form a film that coats the eye with three distinct layers. The innermost layer, which covers the eyeball, is made of a protein called mucin. This layer, secreted by the conjunctiva, coats the cornea and permits an even distribution of the next layer, which is the aqueous layer, made of water and proteins. The outermost layer contains oils that prevent evaporation of the other layers. Every time a person blinks, the tear film is spread over the eye to keep it moist and free of dust and other irritants.
Afterward, tears drain into two tiny openings on the edges of the upper and lower eyelids at the inner corner of the eye. From there, they are channeled by the tear ducts into the nasal cavity, which drains into the throat, and are swallowed. If there are too many tears, they overflow the lower lid and run down the cheek.
Our vision gets blurry when we cry because light has to get through all those layers to get to the retina of the eye. Our tears distort the light we see.
Tears have the job of protecting our eyes, and, surprisingly, they can work in quite complex ways. In addition to keeping our eyes from drying out, tears have a bit of salt in them, which helps prevent infection. They even carry oxygen and some nutrients to the eye’s surface. If something gets in one of our eyes and irritates it, the tear glands flood our eyes with tears and try to flush away the invader. And tear production goes on even when we are sleeping.
People can have trouble with their tear plumbing system. Dry eye syndrome is a common condition, in which the eye is not being kept wet enough to be comfortable. Using artificial tears is the most common treatment. The openings (puncta) that conduct tears out of the eyes can become blocked. A clean, warm, wet washcloth placed over the closed eyes is the recommended treatment. The warmth may open clogged oil ducts. And there is a whole host of other maladies associated with the tear system. Doctors can diagnose and recommend treatment.
Health professionals say that crying is beneficial to health and mental well-being. A good cry is great for body and mind.
Type 1 diabetes, which used to be called juvenile diabetes, is a chronic, lifelong autoimmune disease in which the beta cells in the pancreas’s islets of Langerhans produce too little insulin to regulate blood-sugar levels. Without adequate insulin, glucose (sugar) builds up in the bloodstream instead of going into the body’s cells. The body is not able to use this glucose for energy despite the fact that there are high levels in the bloodstream, which leaves the person feeling hungry. Additional symptoms include thirst, increased urination, weight loss, nausea, and fatigue.
There is one new case per year for every seven thousand children, but the exact cause of juvenile diabetes is a mystery. Genetics play a role, but cold weather and viral infections are thought to be possible environmental factors as well and may trigger an autoimmune phenomenon leading to the destruction of beta cells in the pancreas.
Seven percent of the population of the United States, or twenty-one million people, have diabetes. About 5 to 10 percent of those cases are type 1 diabetes. Most Americans who are diagnosed with diabetes have the less serious type 2, formerly called adult-onset, diabetes. The good news about type 2 diabetes is that many cases can be controlled by diet, weight management, and exercise. But patients often still need oral medication or injected insulin to achieve effective control of their condition. A recent phenomenon has been the marked increase in the incidence of young people being diagnosed with type 2 diabetes (previously rare), which correlates with the “epidemic” of childhood obesity. Many of them are within the age range once associated with type 1 diabetes, and this helped lead to the dropping of the juvenile- and adult-onset labels.
A diagnosis of diabetes is confirmed by a fasting blood test—a patient does not eat anything for twelve hours before the test. Water, tea, or coffee is acceptable, but skip the milk and sugar. Treatment takes two forms: insulin injection to regulate blood sugar levels and treatment for diabetic ketoacidosis (DKA), which can occur when blood-sugar levels do get too high (hyperglycemia). At around 240 milligrams per deciliter, the body looks for other energy sources and uses fat as the fuel source. The fats are broken down and acids called ketones build up in the blood and urine. DKA is a dangerous situation and accounts for most of the hospitalizations due to diabetes. DKA can lead to heart and kidney disease, retinopathy, and neuropathy.
The long-term goals in living with diabetes are to reduce the symptoms and prevent diabetes-related complications, such as blindness, kidney failure, and foot or leg amputations. The ultimate goal, of course, is to prolong life and to make that life as comfortable and meaningful as possible.
On January 12, 2007, Jennifer Strange, a twenty-eight-year-old woman and mother of three children, was found dead by her mother in her Rancho Cordova home. She had taken part in radio station KDND’s “Hold Your Wee for a Wii” contest to try to win a Nintendo Wii game console that went to the contestant who drank the most water without urinating. It is estimated that she drank two gallons of water in a very short period of time. Nearly all deaths related to water intoxication, excluding drowning, have occurred because of drinking contests, hazing incidents, marathon or Ironman races, and parents or babysitters punishing a kid.
Drinking too much water too quickly pushes the normal balance of electrolytes in the body outside safe limits. The level of sodium in the blood must stay within very narrow margins. Too low a concentration of sodium in the blood is called hyponatremia; other causes are not replacing electrolytes after exertion, large burns, severe diarrhea, heart failure, and certain medications. In addition to sodium, other electrolytes that must be kept with a reasonable balance are potassium, chloride, and bicarbonate.
Water enters the body orally and leaves the body in urine, sweat, and exhaled water vapor. If water enters the body more quickly than it can be removed, body fluids become diluted. As the body tries to balance the electrolyte concentration inside and outside its cells, osmosis makes the blood’s concentration of electrolytes—mainly sodium and magnesium—drop relative to the concentration of electrolytes in the cells, causing the cells to swell. If this swelling occurs in the brain, pressure builds up because the bones that make up the skull don’t budge. The brain squeezes against the inside of skull, which impairs brain function. The result may be headaches, nausea, impaired breathing, disorientation, muscle cramps, seizures, coma, and even death.
Drinking too much water also puts a heavy burden on the kidneys. They have to work overtime to filter out the excess water in the circulatory system. The kidneys don’t work like plumbing pipes, which become cleaner the more water you flush through them; over time, unnecessary wear and tear can damage the specialized capillary bed in each kidney, called the glomerulus. The glomerulus is a network of capillaries that performs the first step of filtering blood, and serious deterioration can eventually lead to kidney failure.
The body is marvelous at letting us know how much water we need. Diet, exercise habits, and the environment all play a role. If you eat lots of foods naturally rich in water, such as vegetables, fruits, and whole grain cereals, you may not need to drink very much water. Avoiding salty foods will make you need less drinking water, too. Doctors say that the best guide to how much water we need is our sense of thirst.
This is just a myth; it only feels like your heart stops. A lot of pressure builds up in the chest, and that pressure spike may momentarily change the rhythm of your heartbeat, but it won’t stop your heart.
A sneeze begins with a tickling in the nerve endings that tells the brain it has to get rid of something irritating the lining of the nose. A person takes a deep breath and holds it, the chest muscles tighten, the eyes close, the tongue presses up against the roof of the mouth, and “ah choo,” the breath comes out the nose and mouth at speeds up to 100 mph. And it can spray up to five feet.
A heartbeat starts with a small bundle of tissue called the sinoatrial node, located in the upper part of a chamber of the heart called the right atrium. This natural pacemaker sends electrical impulses down to the right and left atria, then the ventricles to start that once-a-second heartbeat. Sneezing may affect the rhythm of the heart and may even cause the heart to “skip a beat,” or throw the whole beat off, but in no way can it stop the heart. So sneeze away, but cover it up!
Why do people say “bless you” or “God bless you” (“Gesundheit,” meaning “health,” in German, and “salud,” again meaning “health,” or “Jesús” in Spanish) after someone sneezes? There are several origins of this custom.
People in some cultures once thought that when you sneeze, you open yourself, or your soul, to the outside world. And perhaps the soul might escape or demons or evil spirits might get into the body. The blessing is a way to ward off bad stuff.
Another theory of the origin of “God bless you” comes from the time the bubonic plague was sweeping through Europe. There was a lot of sneezing and coughing with the plague. Pope Gregory VII suggested that saying “God bless you” might protect a person from an otherwise certain death.
Whatever the origin, I think it is a very fine tradition and makes us a more civil people.
Every kid knows the joy of spinning around and around, getting dizzy, and trying to walk straight or simply stand up and not fall over, or perhaps of getting on one of those small merry-go-rounds at the park and rotating very fast and getting silly dizzy. What great fun!
This kind of dizziness goes to the heart of how we maintain our balance. There are three mechanisms at work to keep us from falling over. The primary tool for maintaining our balance is our vision. We can see if we are falling over and if things are level.
The second is our vestibular, or inner-ear, apparatus. The inner ear has three semicircular canals, all at right angles to one another and all filled with fluid. We’re using the vestibular balance mechanism of our inner ear when we stand upright, close our eyes, and don’t fall over. When a person spins around and around, they get that fluid moving. When the person suddenly stops spinning, the fluid keeps moving. There is conflicting information fed to the brain between what the eyes see and the messages that inner-ear fluid is sending. So a person feels dizzy for a bit. Astronaut and senator John Glenn had a fall in the bathroom while he was replacing a light fixture. He hit his head and had dizzy spells for some time due to damage to the inner ear.
The third component we use to maintain balance is the kinesthesia or proprioception mechanism. The two terms are often, and at times incorrectly, used interchangeably. Our body sends signals to the brain from our muscles and tendons, or proprioceptors, to give us an awareness of position and movement of our body. Aviators call it the “seat of the pants” sensation.
Dizziness or vertigo can also result from a medical problem; some drugs cause dizziness as a side effect, too. It’s believed that 30 percent of Americans will visit a doctor sometime in their life complaining about vertigo, dizziness, and the accompanying nausea. The nausea is a result of conflicting messages sent to the brain.
In some people, especially older folks, dizziness causes falls and broken bones, including the rather serious hip break or fracture. There is the possibility that one’s hip may break because of osteoporosis, and a fall may result. Many older people become dizzy when standing due to a sudden drop in blood pressure.
Astronaut Alan B. Shepard had severe vertigo after he contracted Ménière’s disease, a disorder of the inner ear. It is caused by a build-up of fluid in the compartments of the inner ear, called the labyrinth. Ménière’s disease can cause severe dizziness, ringing in the ear, and hearing loss. Shepard had such a severe case that he would lose his balance and fall. Shepard eventually got fixed up and flew on Apollo 14: He was the oldest astronaut to walk on the moon (1971), at age forty-seven, as well as the first American to fly in space (1961).
Dizziness, or vertigo, can be related to a neurological condition like multiple sclerosis or Parkinson’s. It can really impact a person’s independence, ability to work, and quality of life. It can lead to depression and disinterest in everyday life.
Doctors report that dizziness can sometimes be a difficult problem to analyze. It could require a battery of tests, including an MRI. The most common diagnosis is peripheral vestibular disease. This disease has a number of causes, from an otolith (stone) rolling around in one of those canals to “inner ear attack.” An inner ear attack is an autoimmune condition that occurs when the body’s immune system attacks the cells of the inner ear, mistaking them for viruses or bacteria.
Our bones are remarkable. Researchers at MIT unraveled the structure of bone with almost atom-by-atom precision. They found that bone is a complex mixture of collagen and mineral that forms into a composite to create a very strong, tough, and reliable material. Bones give our bodies structure, and they can bend, too. But if they bend too much, they break, or fracture. Compare bones to a wooden pencil. A wooden pencil will bend, but if you try to bend it too much, it will break. Bones behave the same way.
The average person will have one or two broken bones in their lifetime. The most commonly broken bone is the clavicle, or collarbone. The bones of the arm, wrist, hip, and ankle all are in the top five. And contrary to popular belief, there is no difference between a broken bone and a bone fracture.
A bone will break if pressure or an impact puts too much force on it. The most common causes are falls, car accidents, and sports injuries, all of which can cause a bone to snap like a wooden pencil or a tree branch.
Bones can also break if they are weakened from within, whether by natural aging or by osteoporosis, infections, or tumors. Bone is live tissue, a honeycomb of tough elastic fibers, minerals, marrow, and blood vessels, and it needs constant repair. Healthy bone is dense, with small honeycomb spaces. In older bones, the repair work slows, so the spaces get larger and the bone is less dense, weaker, and less elastic. In osteoporosis, a common condition in older people, the living bone cells are not able to break down old bone and replace it with denser and healthier new bone. Bone regeneration slows to the point where fewer new bone cells are being created than old ones are being lost. Over time, bones become thinner and are more likely to break.
The risk factors for broken bones include age, being female, low bone density, and a history of bone fractures.
Another cause of broken bones is repeated trauma to a bone over a period of time, to the point where the body can’t keep up with repairing itself. Doctors use the term “stress fracture” to describe this condition; common examples include runners’ ankle bones and hip bones.
But there is good news: Our bones are natural healers. At the site of the break, bones make a lot of new cells. New blood vessels develop that carry nutrients to help rebuild the bones. Those new cells cover both ends of the broken part of the bone and close up the break to make the bone as good as new, and possibly even stronger. Bones heal themselves by absorbing minerals and proteins from the bloodstream. The most important minerals are calcium and phosphorus, which are deposited in the bones to repair the break. Doctors put a broken bone in a cast to keep it immobile and aligned properly while all that depositing is taking place.
A new treatment for broken bones is a bone growth stimulator. The device, worn externally on the body, is used to treat nonunion breaks, where the broken bones have failed to heal. Electromagnetic or ultrasonic waves are delivered to the break site, which encourages bone growth.
There are different kinds of breaks, and X-rays are used to sort of map the break. A hairline fracture is a thin break in a bone. A complete fracture means the break goes all the way through the bone, leaving it in two pieces. A greenstick fracture is a crack on one side of a bone. A comminuted fracture is when the bone is broken into more than two pieces or is crushed. An open fracture is when the broken end of the bone sticks through the skin. Ouch!
How long does it take for bones to heal? Healing takes time, and the exact amount of time depends on the type of fracture and on the person’s age, overall health, nutrition, and blood flow to the bone. A young child may have a bone heal in three weeks, but it may take six weeks for a teenager with the same kind of break. Bone material is created and deposited faster in young children than in teens and adults. What promotes faster healing for all age groups? Good nutrition, which means a balanced diet with all the food groups. Healing bones need more nutrients than intact bones that only need maintenance.
One of the worst things for healing bones is smoking. People who smoke have a much longer healing time and a higher risk of developing a nonunion, or nonhealing, of the bone. Smoking changes the blood flow to the bone, and it is that blood flow that delivers nutrients and cells to promote healing.
Doctors sometimes recommend calcium supplements, but there’s a limit on how much calcium is helpful. The body will reject an oversupply of calcium. A more helpful recommendation than calcium overloading that your doctor can make is to follow a treatment plan, which may include rest, nutrition, and time, and, if need be, healing aids and procedures such as casts, crutches, surgery, or pins.
There is strong evidence that a lifetime daily intake of vitamin D is helpful for anyone who breaks a bone. Vitamin D, along with sunlight, promotes calcium absorption, which makes bones denser and stronger.
If you do not like the bones you have, just wait awhile. The average adult replaces their complement of skeletal bones about every ten years. It takes that amount of time to replace all the calcium in our bones. In fact, the skeleton is always regenerating and adjusting over the course of our lives. Bone remodeling alters our structure as our mechanical demands on our bodies change, and it helps make tiny patches of new bone to repair small damages.
Goose bumps are small bumps on a person’s skin at the base of body hairs. Tiny muscles at the base of each hair contract and pull the hair erect. The most common type of goose bumps is a response to cold. In addition to getting goose bumps, our bodies respond to cold in several other ways. Shivering increases the amount of heat produced by muscles by a factor of three or four times at peak shivering. As the body’s core temperature drops, the central nervous system also restricts blood flow to the limbs and reroutes some of this blood to the internal organs of the body. The limbs get pale and then turn blue.
The animal kingdom also responds to cold. Birds preen and fluff up their feathers in anticipation of approaching cold weather. Fur coats thicken. Migrating animals go south. Some animals hibernate. Small animals eat almost constantly just to stay alive. The smaller the animal, the greater their surface-area-to-volume ratio. Small animals lose a lot more heat through their skin than big animals do. That is why there are very few small animals in arctic regions. Big animals, like polar bears, survive where squirrels would die. To me, the word “Arizona” sounds really good in the wintertime!
Goose bumps can also occur when a person is angry or afraid. Certain noises, such as nail scratches on a blackboard, can trigger goose bumps. Hearing awesome music, or seeing a famous person or someone we love, can produce goose bumps, too. I’m sure we’ve all heard people say something like, “That music was so beautiful it gave me goose bumps.” Research published in the Canadian journal Nature Neuroscience indicates that dopamine is released when listeners are in a strong music-induced emotional state. The “reward” chemical dopamine produces a physical effect known as the “chills,” which causes changes in heart rate, skin resistance, skin electrical conductance, and breathing rate.
A fingernail is produced by living skin cells in the finger. The nail plate is the visible part of the nail. The nail bed is the skin beneath the nail plate. The cuticle is the tissue that overlaps the plate and rims the base of the nail. The nail fold is the skin that frames and supports the nail on three sides. The lunula is that whitish half-moon at the base of the nail, and the matrix is the hidden part of the nail under the cuticle.
Fingernails grow out of that matrix. Fingernails consist of keratin, the same hardened protein in hair and skin. New cells grow in the matrix and push out older cells, which become compacted and assume that familiar flattened, hardened form.
Fingernails grow all the time. They grow faster than toenails. Fingernails grow about three millimeters in a month. A millimeter is about the thickness of a dime. It takes about six months for the fingernail to grow its entire length, from the root to the free end. Growth slows down with age and with poor circulation. The growth rate also depends on the season and on a person’s exercise level, diet, heredity, gender, and age. Fingernails grow faster in the summer, due to exposure to the Sun and an increase in vitamin D. But contrary to popular belief, fingernails do not continue to grow after we die. The skin around the fingernails dehydrates and tightens, making the nails appear to grow.
There are a number of theories about why we have fingernails and toenails. The most common relates to how humans altered or adjusted to a changing environment over many eons. Fingernails and toenails are almost exclusively a feature of humans and primates. Whatever the reason for their existence, fingernails are certainly useful. Fingers are very sensitive; each contains a mass of nerves. Fingernails protect our fingertips. They also make us more dexterous and help our hands do amazing things. Fingernails help us scratch when we itch. They help us peel things like oranges. Fingernails help us undo knots in string and ropes. They help us grasp or pick up things that are very tiny, such as a nut, screw, needle, peanut, or pencil. We use fingernails to grip, rip, and tear. People who have lost fingernails, or toenails, for that matter, can attest to how valuable they are.
Healers have used the general appearance of fingernails as a diagnostic tool since olden times. Some major illnesses can cause a deep groove to form across the nail. Brittleness, splitting, discoloration, thinning, white spots, and Mees’ lines can indicate problems in other parts of the body. Mees’ lines, which are white bands across the width of the nail, appear when a person is poisoned with arsenic, thallium, or another heavy metal. Mees’ lines show up in some patients undergoing chemotherapy, and kidney failure can also cause their appearance.
There are several ways to measure what we are made of. We can classify ourselves as amounts of fat, bones, and muscle. Another way we can appraise ourselves is by percentage of water. About 50 to 60 percent of our bodies is water. It’s a good thing we are warm-blooded; otherwise, we might freeze to death!
At the most basic level, people are made of the same stuff that everything else is made of—namely, atoms. The atoms make up molecules, and the molecules make up chemicals. We can also classify ourselves by the chemicals in us. If we go by chemical composition, we are mostly carbon. We are about 62 percent carbon, 11 percent nitrogen, 10 percent oxygen, 6 percent hydrogen, 5 percent calcium, 3 percent phosphorus, and 1 percent potassium. That gets us up to about 98 percent. The other 2 percent is trace amounts of about twenty-eight other elements.
Yet another way we measure ourselves is by fat content. According to the National Institutes of Health, a healthy adult man should have a body fat of between 13 and 17 percent. A healthy adult woman should have a body fat of between 20 and 25 percent. The ideal percentage of muscle is about 43 percent.
We can compare the efficiency— defined as work done divided by energy consumed—of the human body with the efficiency of other machines. A human can get up to about 20 percent efficiency by cycling on a stationary bike. The top efficiency of a gasoline engine is about 38 percent, but most are around 20 percent. So we are as good as most engines.
The heart is a fist-size, muscular organ that pumps blood. And it is very busy, pumping five quarts of blood every minute, or almost eighteen hundred gallons a day.
The heart has the job of pushing blood through our arteries, which carry oxygen and nutrients to all parts of our body. Blood returns to the heart via veins called the superior and inferior venae cavae to pick up a fresh supply of oxygen and nutrients.
The heart has four chambers. The top two chambers are atria, and the bottom two are ventricles. The right side of the heart pumps blood to the lungs, and the left side pumps blood to the rest of the body. Each chamber has a one-way valve to keep any blood from flowing backward. The top two atria are receiving chambers. The right atrium receives blood from the upper part of the body via the superior vena cava, and blood from the lower extremities by way of the inferior vena cava.
The left atrium receives blood from the lungs. The bottom two ventricles are pumpers, the right pumping blood to the lungs and the left pushing blood to the other organs and tissues. That left ventricle does about 80 percent of the work of the heart. The atria and ventricles work together, alternately squeezing (contracting) and then relaxing. The heartbeat is triggered by electrical impulses that originate in the sinoatrial node, located in the right atrium. Those electrical signals are conducted across both atria by nerve fibers. This makes the atria contract and squeeze blood into the ventricles. The signals from the atrium on each side cross a junction to the ventricle on that side, telling the ventricles to contract and pump blood to all parts of the body.
We are all one heartbeat away from eternity, so it pays to take care of such a vital organ. That means, of course, having a heart-friendly diet that is low in fat, low in salt, and low in sugar (see question 5). And keeping our body weight in check is not always easy, but it is important: Being overweight or obese puts people at high risk of heart disease, which is the leading cause of death in the United States. The toll is over six hundred thousand per year.
We should all get regular aerobic exercise designed to improve our oxygen consumption and raise our heart rate. That could be such activities as walking, jogging, biking, and swimming. There also seems to be a genetic component to having a healthy heart. So be thankful if you have “good heart genes.”
When I was a kid growing up on a farm, we kids would argue about this. The general consensus was that blood was blue when it was in our body but would turn red when it hit the air. Well, we were mostly wrong.
It turns out that blood is never blue. Its color—either red or darker red—is determined by the amount of oxygen and carbon dioxide in the blood. We know that blood contains hemoglobin, which contains iron atoms (see question 4). (Rock formations with a high iron content are reddish in color.) In the lungs, there is a lot of oxygen available, which bonds with the hemoglobin. So blood leaving the lungs through the pulmonary veins—the only veins to carry oxygenated rather than deoxygenated blood—returns to the heart high in oxygen content and bright red in color. The heart pumps this red blood to the rest of the body through arteries to deliver oxygen to tissues, organs, and muscles, where it is used up (see question 18).
The blood returning in a separate set of veins is depleted of oxygen, which has been replaced with plenty of carbon dioxide, giving the blood a much darker red color. And when we look at our veins, the color of the blood appears bluish because some of the dark red color is absorbed by the veins and skin. (This only works for veins because we can’t actually see our arteries through our skin; they have muscular walls that are much thicker than our more thin-walled veins.) Mostly blue color is transmitted.
I used to show the skin-absorption phenomenon to students in science class by taking a small glass tube and filling it with water made bright red using food dye. Both ends were capped with clay. I would place the “blood-filled” glass tube in a glass tray and slowly pour skim milk into the tray. The color of the “blood” seemed to slowly change from a reddish to a bluish tint as the milk covered the glass tube. The milk absorbed some of the longer red wavelengths of light coming from the tube of “blood.” The shorter blue wavelengths of light were transmitted through the milk, yielding a bluish tint to the “blood” tube.
The cause of chicken pox is a virus called varicella-zoster. This highly contagious disease spreads from person to person by direct contact, coughing, or sneezing.
The incubation period is between ten days and three weeks. Most of us who were children before 1995, when the vaccine became widely used, remember the red, itchy rashes and blisters on our skin. And, of course, we remember staying home from school for a few days. Once a child gets over chicken pox, they have lifelong immunity. They never get it again.
Treatments include cool, wet compresses or baths, calamine lotion, and acetaminophen, such as Tylenol. Aspirin should be avoided. It can cause Reye’s syndrome, a potentially fatal disease that has a detrimental effect on many organs, including the brain and liver. Ibuprofen, the medicine in Advil, may cause more severe secondary infections and should also be avoided.
Getting the chicken pox (varicella) vaccine can protect children from the chicken pox virus. The vaccine reduces the chances of getting chicken pox. Vaccinated kids who do get it will have a much milder case.
Kids, in most but not all states, must be vaccinated for chicken pox before they enter preschool or kindergarten. Typically, kids receive the vaccine between the ages of twelve and eighteen months, plus a booster before starting kindergarten. A teenager who has not received an inoculation for chicken pox has an increased risk of contracting it in adulthood, and chicken pox is harder on adults than it is on children. Adults tend to get sicker. Stacey Rizza, chair of the HIV clinic at Mayo Clinic, states that “getting chicken pox as an adult can lead to more severe symptoms because your immune system is not as young and ready to attack, so you get a little sicker.” There is also the added danger of pneumonia. Adult inoculation against chicken pox may require two shots.
Shingles is a second eruption of the same varicella-zoster virus that causes chicken pox. And shingles can be bad news. After an attack of chicken pox, the nasty virus can hide among nerve cells of the ganglia and spinal cord. A ganglion is a biological tissue mass, most commonly a mass of nerve cell bodies.
Because the virus may never have fully disappeared from the body, it may lie dormant for years. Doctors do not know why the virus flares up suddenly after years of inactivity. Disease, stress, age, or a weakened immune system can cause the virus to reactivate and reproduce. It travels along the path of a nerve to the skin’s surface, where it causes shingles. Shingles is characterized by burning pain, sensitive skin, rash, and blisters. The blisters pop and ooze. The whole process unfolds over three to four weeks. Antiviral drugs, such as Zovirax, Famvir, or Valtrex, are prescribed for treatment.
There are different types of memory, short-term and long-term, and the brain stores them in different places. Short-term memory is good for just a few minutes. If someone gives you a seven-digit telephone number to call, you store that information in short-term memory. Most of us will have forgotten it an hour later. The storage of information in short-term memory is limited in capacity and time. Long-term memory stores things you remember for a year, five years, ten years, or a lifetime. If short-term memories are practiced often enough, they turn into long-term memories. That’s the reason most people know their Social Security number “by heart”; they’ve written it down or “practiced” it often enough.
The brain’s hippocampus is essential to taking information from short-term memory and putting it into long-term memory. Some scientists believe that long-term memories are maintained by stable and permanent neural connections widely spread throughout the whole brain. One of the main functions of sleep is the consolidation of information. The hippocampus replays information from that day and speeds it along to long-term memory.
Memory loss is the most common cognitive impairment in people with severe head injuries, including some loss of specific memories and partial inability to form or store new ones. Their long-term memory tends to be all right. They will say to their doctor, “I can remember something that happened ten years ago in great detail, but I can’t recall something from ten minutes ago.”
It is common for brain-injured people to forget events that occur right before, during, and right after the injury. This temporary loss is caused by the brain’s swelling, which presses the brain against the inside of the skull. Memory usually returns when the swelling goes down.
So why do these injuries affect short-term memory? It has to do with how the brain processes information. Info from our senses goes through a filtering process, sort of like how mail is sorted at the post office. When the brain is injured, the areas that do the processing can get pressed or squeezed due to swelling. When this happens, a large amount of information and sensory data coming into the brain does not get processed. The information is not sent to the right places. The mail room of the brain can’t do its job.
The brain can also have another type of memory problem. Once data is stored in the brain, it has to be able to retrieve it. But the brain can have a problem retrieving stored information. We’ve all had this type of problem, but in the brain-injured person it is much worse. You meet someone on the street. You know who they are but can’t quite come up with their name. A few minutes or hours later, you recall the name. The brain has been searching and trying to retrieve that bit of information. For people with brain damage, retrieval of information may be difficult or impossible because the connections have been permanently lost.
Most brain injuries are caused by car accidents, motorcycle and bicycle accidents, and falls around the house. But recently we are hearing about head injuries to our soldiers who have served in Iraq and Afghanistan from those improvised explosive devices (IEDs). Also, there is now a lot of concern about brain damage in football, where head-to-head collisions can cause concussions, confusion, drowsiness, nausea, disorientation, lack of coordination, and slurred speech, in addition to long-term effects. The NFL is looking into this matter. There is also much concern about possible brain damage to high school and college football players.
Recent research indicates that a third type of memory, called immediate memory, may be at play in the brain. Immediate memory is a blanket term that may include short-term memory and there is overlap between the two.
Most researchers agree that the study of the human mind is in its infancy. It is an exciting area of study, and there is much to learn.
There are ten or eleven main organs and a whole bunch of little ones. The exact number is hard to come up with, because there are different views on what qualifies as an organ. Do ligaments and tendons count as organs? It’s difficult to decide which are organs and which are just parts of a larger system.
An organ is defined as a structure that contains a collection of tissues working together for a common purpose. Medical dictionaries also define an organ as a relatively independent part of the body that carries out one or more special functions.
The main organs are the brain, heart, lungs, liver, kidneys, stomach, bowel, intestines, and skin. The skin is the largest organ. It accounts for about 15 percent of our body weight. The skin protects everything that lies beneath it. It alerts our body to dangers and acts as a cushion to blows. Our skin is a barrier and the first line of defense against invading parasites and diseases.
The largest internal organ is the liver. It is also the heaviest, weighing in at about 3.5 pounds. The liver regulates most chemical levels in the blood and excretes bile, which helps break down fats. The longest and strongest bone is the femur, the long upper leg bone in the thigh. The largest artery is the aorta, the big one that sits atop the heart and carries oxygenated blood to all parts of the body, while the largest vein is the inferior vena cava, which returns blood from the bottom half of the body back to the heart.
Biology and anatomy students have used mnemonic, or memory, devices for years to remember material that just might show up on tests. A few examples: GRIM END is an explanation of the seven aspects of life: Growth, Reproduction, Irritability, Movement, Excretion, Nutrition, and Death. MRS GREN for the seven things all living animals do or have. Movement, Reproduction, Sensitivity, Growth, Respiration, Excretion, Nutrition. I Picked My Apples Today is a mnemonic for remembering the phases of mitosis, the process of cell division, which allows our cells to multiply into all the organ systems of our bodies: Interphase, Prophase, Metaphase, Anaphase, Telophase.
Most people are more interested in how to stop hiccups! Hiccups are unintentional movements, or spasms, of the diaphragm followed by rapid closing of the vocal cords. A spasm is a sudden muscle jerk. The diaphragm is a thin dome-shaped muscle at the bottom of the chest. It separates the organs in the chest (heart and lungs) from the organs in the abdomen (stomach, liver, spleen, pancreas, gallbladder, and intestines). When a person inhales, it is because the diaphragm is pulling down to help pull air into the lungs. When a person exhales, it is because the diaphragm is pushing up to help push air out of the lungs. Intercostal muscles, which lie between the ribs and have a lesser role in breathing, are also affected by hiccups. These muscles help us breathe, speak, sing, and cough.
When the diaphragm becomes irritated, it misbehaves. It pulls down in a jerky way, sucking air into the throat suddenly. When that rushing air hits the voice box, it makes the sound we know as a hiccup. The causes are different for each person. But one thing is common to all hiccup cases: irritation of the diaphragm. Hiccups can be caused by eating too much or too fast. Drinking very hot or very cold beverages can also bring on hiccups. Other causes include cold showers, entering or leaving a hot or cold room, or any sudden excitement or stress. Eating spicy foods, drinking alcohol, breathing in suddenly, sneezing, laughing, and coughing can all lead to hiccups. Sometimes the cause is unclear; very often, hiccups start for no apparent reason. Sometimes when a woman is pregnant, the fetus even gets hiccups inside her!
Hiccups are not a serious problem; they’re just an annoyance. They usually go away by themselves in a few minutes. Just as there are many causes, there are numerous methods people use to stop hiccups. A favorite cure is to drink a glass of water. Another popular method is to stretch the diaphragm by holding one’s breath while raising one’s arms. Anything that promotes build-up of carbon dioxide in the blood will stop hiccups.
Distractions, such as saying the alphabet in reverse or concentrating on a painting, seem to work for some people. A half-teaspoon of dry sugar or honey might work, too. If the vagus nerve that runs from the brain to the stomach is stimulated, hiccups can be relieved. Having someone frighten you or startle you may work. A tug on the tongue works for some people.
Children tend to “grow out” of having hiccups by the late teen years. While most people get hiccups from time to time, the frequency of hiccup episodes decreases with age and maturity.
In extreme cases, people might have to see a doctor. A doctor can interrupt the hiccups by giving muscle relaxants, sedatives, or anticonvulsive drugs.
Skin color result from the presence of a pigment called melanin, located in the epidermis, or outer skin layer, and produced by cells called melanocytes (see question 3). Melanin acts as a protective shield against ultraviolet radiation and helps prevent sunburn damage that can lead to melanoma (skin cancer).
There are several theories concerning the evolution of skin color. A long-held theory suggested that people in the tropic regions near the equator developed dark skin to block out the stronger Sun. The weaker the ultraviolet light, the lighter the skin. The greater levels of melanin in dark-skinned people would prevent them from overdosing on vitamin D, which can be toxic in high concentrations. However, critics of this theory say that it is impossible to overdose on natural levels of vitamin D.
Humans need some ultraviolet rays to penetrate the skin in order to produce vitamin D, which is needed for the intestines to absorb calcium and phosphorus from food and deposit it in our bones. Lack of vitamin D results in rickets in children and osteoporosis in adults (see question 45). People living above fifty degrees north latitude or below fifty degrees south latitude have a much higher risk of vitamin D deficiency. Only the ability to fish, which provides access to food rich in vitamin D, allowed early humans to live in temperate and polar climates.
A newer theory proposes that differences in skin color are related to the fact that ultraviolet light from the Sun affects the level of folic acid (a type of vitamin B) in the body. An hour of intense sunlight can cut a light-skinned person’s folic acid level in half. People who live in the tropics developed dark skin to block out the Sun and protect their folate reserves. People who live farther north or south evolved to have fairer skin so they could absorb more ultraviolet light from the Sun and produce needed vitamin D, but they also need to get more of their folic acid from their diet. Fair-skinned people also have a higher risk of skin cancer. Low levels of folic acid are associated with neural tube defects, such as spina bifida. For this reason, women in the early stages of pregnancy should avoid tanning booths. Women of child-bearing age should make sure to get enough folate in their diet even before they become pregnant.
Some anthropologists believe that both theories may be correct. They believe people close to the equator developed darker skin to block out the Sun and protect their body’s folic acid reserves. People closer to the polar reaches developed lighter skin to produce adequate amounts of vitamin D during the longer winter months.
The technical term for tone-deafness is amusia, and one in twenty people have it. Tone-deafness is the inability to distinguish between musical notes. To clarify definitions, “tone,” “pitch,” and “frequency” all mean the same thing, namely the number of vibrations per second. Different frequencies of vibrations create different sound waves, which we perceive as different notes. There is not much correlation between a good singing voice and the ability to hear tones accurately. Some people who have bad singing voices hear music just fine. However, the inability to keep time with music (or lack of rhythm) and the inability to recognize common songs are indications of tone-deafness.
There has been some recent and intriguing research on this subject. New brain-imaging techniques can measure the density of the white matter, consisting of nerve fibers, that provides paths between the right frontal lobe and the right temporal lobe. The right frontal lobe is where higher thinking occurs, and the right temporal lobe is where sound processing takes place. In tone-deaf people (amusics), the white matter connecting them is thinner, which weakens the connection between these two parts of the brain. Studies show a direct correlation: the thinner the white matter, the worse the tone-deafness. For a tone-deaf person, the neural highway is a dirt road and not a four-lane interstate!
Some believe there is an overlap between how the brain handles music and how it handles speech. Music involves the whole brain. Other researchers believe that musical perception and thinking occur separately from other functions. Many scientists say that there is a strong genetic component to tone-deafness.
You can go online and check your ability to perceive tones at delosis.com/listening/home.html. The site is from the Harvard Medical School.
Charles Darwin, General Ulysses S. Grant, President Theodore Roosevelt, and William Butler Yeats were all tone-deaf. These men achieved greatness despite their tone-deafness.
Human hair is made of the same stuff that horns, fingernails, cat and dog claws, cow and horse hooves, and bird feathers are made of: a protein called keratin. And it grows out of a tiny opening in the skin called a follicle. One kind of keratin is made of long protein chains, and the coiled chains wind around each other to resemble a shape much like a twisted telephone cord.
Keratin was first described by Linus Pauling, who won two Nobel Prizes; one was in chemistry, for applying quantum physics to chemical bonding in chemistry, and the other was the Nobel Peace Prize, for his opposition to the spread of nuclear weapons.
All parts of the body have hair except the lips, palms, and soles of the feet. Adults have about five million hairs growing out of the body. That’s about the same number as a gorilla. Thank goodness, human body hair is thin and short and hard to see. Gorilla hair is thick and long and, well, hairy.
It’s widely held, though not entirely proven, that about eighty hairs fall out of our head each day. Not to worry. Our head has over one hundred thousand hair follicles. Plenty to spare.
Some people have curly hair and some have straight hair. It depends on the shape of the follicle out of which the hair is growing. Straight hair grows out of a round follicle. Curly hair comes out of an oval follicle; it bends because its cross section is oval, not round.
Hair color is caused by the same chemical pigment that determines skin color—namely, melanin (see question 24). White hair means no melanin. Lots of melanin means black hair. Smaller amounts of melanin mean blond, red, or brown hair.
Hair’s function is to keep us warm. When we are chilled, we get goose bumps (see question 15). Those temporary bumps are caused by muscles attached to hair follicles pulling the hairs upright.
I’ve been watching the hair fall on the cloth when I go to the barber. Still a lot of brown and dark-brown color there, but I do believe I notice some hairs with a grayish tint to them!
Things wear out, and our bodies are no exception. Aging is a natural occurrence and not a disease. There seem to be two aspects to aging: nature (genetic influences) and nurture (environmental influences). Aging, to a large extent, is under genetic control. Many scientists say that we are genetically programmed to die in less than one hundred years.
Individual cells of our body have different life spans. Stomach cells last about two days, red blood cells 120 days, bone cells about thirty years, and some brain cells a lifetime. But while these cells reproduce before they die, the organism as a whole has a limited life span. No matter how well we take care of ourselves, our bodies wear out, shut down, and die.
The other aspect to aging, the nurture, or environmental, part, is largely the accumulation of changes, or mutations, in our DNA. These lead to loss of metabolic capacity; muscle and skin cells slowly lose their ability to regenerate with time.
The good news is that we do have some control of the aging process. Good diet, moderate use of alcohol, avoidance of tobacco, avoidance of overexposure to the Sun’s ultraviolet rays, and an exercise regimen all contribute to slowing the aging process.
How long do things last? A sequoia tree will live for 2500 years. A mouse typically lives fewer than four years. A housefly has a life span of twenty-five days. A facelift is good for ten years. A pencil will write 45,000–50,000 words. A dollar bill is in circulation for eighteen months.
As for us, American men live about seventy-four years and women around seventy-nine years on average. The leading causes of death in the United States are heart disease (1 out of 3) and cancer (1 out of 4). Many dread diseases, such as polio, typhoid, smallpox, and diphtheria, have been conquered, so accidents are now the leading cause of death for people fifteen to twenty-four years old.
Some scientists believe we may one day unlock the secret of immortality, but do we really want people to live forever? Think of the overpopulation. Think of the lines at McDonald’s!
Eye twitches are harmless, involuntary spasms of the tiny muscles surrounding the eye. Eye twitching comes from squinting too much, or simple fatigue, or drinking too much coffee, or dry eyes, or by staring at a computer monitor or television set for too long a period of time.
People who spend a good part of the day at a computer screen are prone to eye twitches. Spasms occur with overuse of any muscle in the body. So simply resting the eyes will take care of most eye twitching. Blinking now and then helps.
Most eyelid twitching disappears without any treatment. But, if you want to stop the twitching dead in its tracks, try rinsing the eyes with warm water, administering antihistamine eyedrops, applying warm compresses, or taking a warm bath. Minor eye twitching, the kind that most all of us experience, usually does not worsen. Some people have eye twitches on one side of the face and not the other.
Blepharospasm is a medical term for the twitching of one or both eyelids, commonly associated with stress. These spasms can last a day or so, and then they usually disappear. When they don’t, the medical profession has used Botox injections to relax the surrounding muscles. Botox is the preferred treatment for most sufferers.
Blepharospasm can be one of the side effects of medications used to treat epilepsy and psychosis. Severe types of blepharospasm can be attributed to dry eyes, Tourette’s syndrome, or neurological problems, such as epilepsy. These severe types require a doctor’s care.
Our bodies have wonderful defense mechanisms against threatening, low temperatures. When we are exposed to cold temperatures, the pilomotor reflex triggers an involuntary muscle contraction that raises the hairs on our skin, producing goose bumps. This traps air near the skin, thereby retaining heat for the body. When we shiver, muscles contract and relax quickly, producing heat. Shivering continues until enough heat is produced. Shivering increases body heat being generated by our muscles many times over. Finally, the brain goes into a survival mode by sending messages that restrict blood flow to the limbs. Blood is shunted to the internal organs. Arms and legs get pale and turn blue.
How cold can we get and still live? Hypothermia sets in below a body temperature of ninety degrees; we lose the ability to shiver and speech becomes slurred. At around eighty-six degrees, we become unconscious, sink into a coma, and become rigid.
Staying dry is important. We lose twenty-five times more body heat if we become wet, such as when we break through ice and fall into the water. Warren Churchill, fishery biologist with the Wisconsin Department of Natural Resources, is said to be the “coldest man alive.” In April 1973, Churchill fell into chilly Lake Wingra near Madison. His core temperature went down to sixty-one degrees. Doctors put him in a special blanket that had warm water circulating in tiny tubes. Churchill shivered so badly doctors had to inject a drug that paralyzed his body. At such extreme temperatures, shivering is so hard on the body that muscles can be strained and torn.
There are several types of mental defects that involve an extra chromosome. The most common is Down syndrome. In 1866, an English doctor by the name of John Langdon Down published an essay in which he described a set of children with distinct facial features.
There are different types of Down syndrome. Down syndrome is caused by abnormal cell division, most often in the woman’s egg before or at the time of conception. Children inherit forty-six chromosomes, twenty-three from each parent. Genes grouped together make up chromosomes. Chromosomes carry the genetic material DNA, or genes. One of the twenty-three pairs of chromosomes, called X and Y, determines the sex of the child. DNA in other chromosomes determines such things as blood type, hair and eye color, and risks for certain diseases.
Defects in chromosomes can cause changes in body processes and functions. Sometimes these changes are undetectable. Genetic defects can pass from parent to child or can occur because of a new mutation. The genetic cause of Down syndrome is full trisomy 21, with a whole extra twenty-first chromosome; in rare cases, Down syndrome can also be caused by inheriting merely some of this chromosome’s genes. Down syndrome occurs when there is an error in cell division. In 95 percent of the cases, one cell has two copies of chromosome 21 instead of one, so the resulting fertilized egg has three copies of chromosome 21 instead of two, hence the name trisomy 21.
Some general characteristics of Down syndrome include reduced height, poor muscle tone, broad neck, shorter-than-normal arms and legs, protruding abdomen, flat nasal bridge, and abnormal shape to the ears.
Severe mental retardation is rare, but most Down syndrome children have reduced intelligence ranging from mild to moderate. Some Down syndrome children have heart defects or vision problems, and they may suffer from hypothyroidism and respiratory problems. Women over thirty-five have an increased risk of having a child with Down syndrome. The risk increases with advancing age.
Life is precious, and with love, care, and education, most children with Down syndrome can lead productive lives.
Many living things, including us humans, grow by cell division. Each of our cells has a nucleus, and during a process we call mitosis, the nucleus divides, creating two cells from one. Each new cell receives a copy of the parent cell’s genetic material.
Cells are forever dividing, creating more cells and leading to tissue and bone growth. Organs grow, skin grows, and everything in the body just keeps getting bigger through childhood. The human body grows constantly and steadily from birth to about age eighteen or twenty. You are not likely to get any taller after age twenty. Of course, there is the possibility of getting wider. Bone growth—in leg bones in particular, because they grow on both ends—is what determines how tall we are (see question 39). Bones get longer, but not much wider, until we get to our late teens, when bones generally stop growing altogether.
Bone growth and height depend on your genes to a large extent, and somewhat on your diet. Bones need calcium and vitamins. So drink milk and skip the sugary drinks, or at minimum, limit your intake. Muscles grow along with the bones, and most of their growth is automatic, although some muscle growth is only triggered by exercise. Use it or lose it!
The pelvis widens one inch between the ages of twenty and eighty, even if a person watches their weight and keeps the same level of body fat. That means about a three-inch increase in waist size. Sometimes life is not fair!
The skull also continues to grow larger as we age, and the forehead shifts forward a bit, making the cheekbones recede slightly. Growth rate is not uniform for all body parts. When a baby is born, its head size is nearly that of an adult’s, but the lower parts of the body are much smaller. Then, as a child develops, the head grows very little but the legs, arms, and torso increase a great deal in size. Heredity determines growth rate to a great extent, but nutrition, exercise, injury, and disease are all factors.
While body growth is so complicated that some of its workings elude us to this day, again, everything comes back to one thing: cell division.
The brain has been referred to as gray matter since at least 1840. Truth be told, the brain is a pinkish, fleshy color. The very center of the brain is an off-white shade. The brain is very soft tissue, having the consistency of pudding, and it weighs about three pounds and has a volume of 1300 cubic centimeters (about 18.3 cubic inches). Brain weight and size vary with the size of the individual.
Each of the 100 billion neurons in the brain has about seven thousand connections to other neurons, creating a huge network of more than 100 trillion synapses. Each connection is “on” or “off,” like transistors in a mega-computer.
The brain uses about 20 percent of our total oxygen intake and about 25 percent of the glucose we consume. The oxygen is used to get energy from the glucose, which is the brain’s source of energy. If the brain’s oxygen is cut off, permanent brain damage occurs after four minutes. Hypoxia means low on oxygen and anoxia means total lack of oxygen.
There are three main parts to the brain: the cortex, the limbic system, and the brain stem. The cortex handles the most complicated things, such as thinking, making decisions, and recognizing sights, words, sounds, and sensations. We depend on the cortex for playing sports and music and for writing. The limbic system is involved with survival. It lets us know when we need to eat, drink water, and put on a coat. The limbic system warns us of dangers and makes us aware of threats, and it’s where we experience pleasure and happiness. The brain stem connects the brain to the spinal cord, which runs down through the backbone. The brain stem controls heart rate, breathing, and other vital functions. If it is badly damaged, a person can lose consciousness and lapse into a coma. The cortex needs the brain stem to keep it alive.
A whole slew of things can go wrong with the brain. Heart attack, suffocation, drowning, high altitude, and head injury can all put a damper on a healthy brain.
There are two kinds of strokes both caused by interruption of blood flow to part of the brain. A blood clot formed in a blood vessel can break off and block an artery in the brain, causing a thrombotic stroke. An aneurysm happens when an artery wall is weakened. The damaged area can swell and apply undue pressure to the surrounding tissue, or burst, causing uncontrolled bleeding and disrupting the brain’s blood supply; this is called a hemorrhagic stroke. Like most of the body’s tissues, the brain can develop tumors, growths caused by runaway cell division. Malignant, or cancerous, tumors invade surrounding tissue and can caused massive damage or spread to other parts of the body. Benign, or noncancerous, tumors do not spread or attack other tissue, but they can grow quite large, putting pressure on adjacent brain tissue.
The abuse or misuse of legal and illegal drugs can damage nerve cells in the brain and lead to permanent brain damage.
Dementia is a general term that describes a wide range of brain declines, such as memory loss, deterioration of thinking skills, and the inability to perform everyday activities. Alzheimer’s accounts for about 50 to 70 percent of cases.
Sometimes a medical examiner or coroner will order an autopsy of a body (see question 57). The reason, of course, is to establish cause of death. As part of most autopsies, the brain is removed. The medical examiner uses an electric saw, called a Stryker saw, to make a round cut through the top of the skull. The cap of skull bone is removed. The medical examiner employs a scalpel to cut the tissue that connects the brain stem to the spinal cord. The brain can be pulled out and stored in a solution to keep it available for further examination.
Albert Einstein’s brain was removed within a few hours of his death in April 1955. It is well worth reading about the journey his brain took the last nearly 50 years—try Carolyn Abraham’s Possessing Genius.
The brain is a wonderful instrument, and it makes us who we are; our bodies are just along for the ride, so to speak, and, when separated from the ingenuity of our brains, are quite utilitarian. The brain is so complex, it has been referred to as one of the last frontiers of the unknown, alongside outer space and the deep ocean.
Our brain is so magnificent and exquisite that it behooves us to take good care of it, for no other reason than it is the only one we will ever have. Realize that it is not wise to endanger our brain by drug or alcohol misuse or by failure to wear bike helmets or seat belts. And we know that, like our muscles, our brain needs exercise—in this case, by lifelong learning, although physical exercise benefits our brain, too.
A person experiencing a heart attack or suffering from angina can take nitro pills, short for nitroglycerin pills, which rapidly open blood vessels. Angina pectoris is chest pain that occurs when there is not enough blood flow to the heart. The medication dilates, or opens, the coronary arteries to the heart, which reduces the burden on the heart, and the pain.
Nitroglycerin comes in a fast-acting tablet or in spray form. Both are applied under the tongue. A sufferer can use the tablets for fast relief in addition to wearing a longer-acting nitro patch. Nitroglycerin tablets are usually taken every five minutes, up to a total of three tablets. If the person is still having heart pain, they had better go to the emergency room and see the doctor immediately.
The nitro pills do come with some warnings. Headache, dizziness, and light-headedness are common side effects. We see all those erectile dysfunction drugs (Viagra, Levitra, Cialis) advertised on TV. The announcer always reminds the viewer (in a low and fast-talking voice) not to combine these drugs with nitroglycerin medications. That might lower blood pressure to a dangerous, life-threatening level.
Mucosa, or mucous membranes, is the moist tissue that lines particular organs and body cavities throughout your body, including your nose, mouth, lungs, and gastrointestinal tract. Glands along the mucosa secrete mucus (a thick fluid). Placed beneath the tongue, nitro is absorbed directly through the mucosa into the bloodstream. With this method, the nitroglycerin is absorbed within a few seconds, faster than when the nitro pill is swallowed, digested, and absorbed.
Aspirin is a well-known treatment for preventing heart attacks, too. Aspirin thins the blood by reducing the clumping action of platelets. Many doctors will recommend a daily regimen of low dosage aspirin, usually 81 mg, for their heart patients.
One of the benefits of writing a science column is that I have an excuse to look up a lot of fascinating stuff. It makes me realize how much I have to learn about so many different topics. It also gives me an opportunity talk to people who are experts in their chosen profession. To make sure I answered this question exactly right, I did some of my own research and talked to a real, live anesthesiologist.
On October 16, 1846, William Morton, a Boston dentist, used an ether-soaked sponge to sedate a printer named Gilbert Abbott. Then Dr. John Collins Warren removed a vascular tumor from the patient’s neck. The patient later informed the onlookers that he had experienced no pain at all. Several men claimed to be the first to make use of anesthesia, including Crawford Long, Horace Wells, and Charles Jackson. Jackson also takes credit for the telegraph, an invention we attribute to Samuel Morse. A new era of medicine had begun.
Today, there are four basic types of anesthesia: general, regional, and local anesthesia and sedation. Each type has an effect on a different part of the nervous system. General anesthesia affects brain cells and causes a person to lose consciousness. Regional anesthesia is administered at different levels of the nervous system to block nerves, while local anesthesia is for a small, specific area. Regional anesthesia may include spinal blocks, epidural blocks, or nerve blocks. Nerve blocks may affect an arm or leg that is being operated on by the surgeon.
Sedation is like twilight sleep. Some of the drugs used for general anesthesia can be used for sedation, but at a lower dose. Examples would include novocaine employed by the dentist or a topical anesthesia used to numb the skin surface. (Sedated is kind of like the state of those soon-to-graduate seniors at the high school. Ha, ha . . . a little joke.)
General anesthesia works on the cerebral cortex of the brain, the thalamus, and the brain stem, resulting in immobility. It also affects the brain stem’s reticular activating system (RAS), which leads to unconsciousness. The RAS regulates our sleep-wake transitions. So a person under proper general anesthesia is pain-free, immobile, and unaware of what is happening to them. When the patient wakes up, they have no memory of the period of time under anesthesia.
I recently had eye surgery using general anesthesia. I always wondered how the doctor knew how much anesthesia to give a person: too much and I go to that “great classroom in the sky,” not enough and I wake up during the operation. And I wasn’t keen on either condition. So, the anesthesiologist told me, he monitors heart rate, heart rhythm, blood pressure, breathing rate, and the oxygen content of the blood.
General anesthesia can be given as an inhaled gas or as an injected liquid. There are several drugs and gases that can be used alone or in combination. The potency of an anesthetic is measured as minimum alveolar concentration (MAC). “Alveolar” refers to tiny sacs in the lung through whose walls gas exchange with the bloodstream takes place. MAC is the alveolar partial pressure at which 50 percent of humans will not move from a painful stimulus, like a skin incision.
Researchers say it is in the genes. It’s the same reason some people are brown-eyed and some are blue-eyed. The Human Genome Project tends to support the theory that a single gene is responsible for handedness. One of every ten people is left-handed, with males outnumbering females 1.2 to 1. Being left-handed implies a preference for using the left hand for writing, pointing, throwing, and catching. Left-handers use the left foot for kicking, the start of running, walking, and bicycling. Being left-handed also means having a dominant right side of the brain. Left-handers may also have a dominant left eye, which they use for camera sights, telescopes, and microscopes.
In the past, there was not much sympathy for lefties. Sometimes there was enormous effort by parents and teachers to force left-handed kids to write right-handed, which led to rebellion, frustration, stuttering, dyslexia, and hatred of school. Kids were often labeled clumsy and awkward.
We seem to be much more enlightened about left-handedness these days. Most parents seem to let their children find their own handedness and accept the outcome. Left-handers even have their own day, August 13, on which they can celebrate their uniqueness.
Still, most tools, utensils, and office gear are made for right-handed people. When pants have only one back pocket, it’s always on the right side. Lefties have to reach for it with the “wrong” hand. Piano keys are arranged so the right hand plays the melody and the left hand plays the accompaniment. Cars have the stick shift on the right. Camera shutter buttons are on the right. The most frequently used keys on a computer, such as enter, backspace, arrows, and the number keypad, are all on the right.
“Southpaw” has its origins in 1880s baseball slang, when baseball diamonds were often arranged so the batters would face east, to avoid looking into the afternoon Sun. The pitcher’s left hand, or “paw,” would therefore be on the southern side.
Finally, superior creativity, genius, and career success have been associated with left-handedness. There are long lists of famous left-handed people, especially in the arts and sciences. They include Julius Caesar, Michelangelo, Albert Einstein, Ted Williams, Ronald Reagan, and Jay Leno. One of my three brothers is left-handed, and he makes more money than I do! My four-year-old grandson is left-handed, and his grandparents know that he is a genius! But you could make endless lists of right-handed success stories, so I’m not convinced that there is any real advantage or disadvantage of being a lefty.
Some people get gray (or white) hairs in their twenties, and others still have dark hair well into their seventies and eighties. The process of graying can occur gradually over many years as individual hair follicles stop producing color, or it can happen within a matter of months or a few years. How long depends a lot on genetics. Also, our changing hair color depends on how dark the rest of the hair is to begin with.
Individual hairs don’t actually “turn” gray—they grow in that way. Every day, hairs fall out and new ones emerge in their place. As the hair grows in the follicle, color is deposited into the new growth in the form of two substances, melanin and pheomelanin, which all people have in varying quantities. Melanin produces the hair shades blond, brown, and black, depending on the concentration of pigment in your hair. Pheomelanin produces red hair and the reddish undertones seen in hair. When one of your follicles stops producing these colored pigments (usually with age), the next hair growing out of that follicle will grow in gray. Why this happens is one of the mysteries of aging.
Having gray hair doesn’t mean a person is not healthy. You may choose to color your hair for cosmetic reasons, but gray hair is nothing to be alarmed about.
A number of external causes can make hair gray. According to most sources, smoking is a big reason. People who smoke are four times more likely to be prematurely gray. (Some evidence, by the way, links smoking to early baldness, too.) Early graying (or balding, for that matter) is not a sign of early aging. Despite some reports, no solid link has been found. Most people, especially those with dark hair, will begin to notice a few white hairs by their late twenties or early thirties.
The human eye and brain work together to perceive color. The retina is the light-sensing structure on the back of the eye. The center of the retina contains about six to seven million cones. Different ones are sensitive to red, green, and blue light.
Rods, located on the periphery of the eye, are sensitive to dim light and handle vision in low light. Each eye contains about 130 million rod cells. When light hits the rods and cones, complex chemical changes create electrical impulses that are sent to the brain via the optic nerve.
White light—the visible part of the light from sources such as sunlight, incandescent light, and fluorescent light—is made up of seven colors. They are the ROY G BIV colors of red, orange, yellow, green, blue, indigo, and violet. Waves that are longer than red, called infrared, are not detected by the human eye. Waves shorter than violet, named ultraviolet, also cannot be seen by the human eye.
The ROY G BIV colors were named by the English physicist Isaac Newton. Of those seven colors, three are considered the additive primary colors for light. They are red, green, and blue. These same three colors are used in color television and color display panels
In about 1680, Newton found that color is not “built into” an object. The red is not “in” the apple. Rather, the surface of the apple is reflecting some wavelengths of light and reflecting other wavelengths of light to the eye (see question 59). The red apple reflects red light to the eye and absorbs the remaining six colors. We perceive only the reflected light. So we say the apple is red. An object appears white if it reflects all the wavelengths (colors). An object is black if it absorbs all the colors of the visible spectrum. A yellow object will reflect red and green and absorb blue.
The subtractive primary colors for printing, paints, pigments, and dyes are cyan, magenta, and yellow. These are the inks used on rollers when color pictures in magazines and newspapers are printed. These colors are often referred to as CMYK. The K is for black ink.
All of us are touched by cancer, either personally or through relatives and friends. Cancer is the second leading killer in the United States, right behind heart disease. One of the problems with a cure is that there is no single type of cancer. Cancer is really an assortment of about two hundred diseases. But they all have one thing in common: abnormal and uncontrolled growth of cells. Cancer is cell division gone wild! The growths and tumors destroy body tissue and may spread to other parts of the body.
A large study of almost ninety thousand twins was conducted in Norway, Sweden, and Denmark in order to determine the degree to which genetics play a role in cancer. Twins are ideal subjects for study because they have similar—and in the case of identical twins, nearly identical—genetic makeups. The researchers found that genes don’t play as big a role as once thought. It’s environmental factors that a pair of twins don’t share that are far more important. Smoking, eating too much, eating the wrong foods, lack of exercise, and exposure to pollution and radiation were far more significant factors than genetics. The twins who generally took better care of themselves had a 90 percent chance of not getting the same cancer as their siblings.
The study suggests that we have some control over whether we get cancer and that we can reduce the risk. Early detection plays a large role in the cure rate for cancers. In many cases, the air we breathe and the water we drink are much better than they were just thirty or forty years ago. But there’s a long way to go. We continue to ingest a lot of junk chemicals in the food we eat. Just take a look at the content labels on, say, crackers, ice cream, soda pop, or meats. Our diets are loaded with way too much fat. Our cars, trucks, and coal-fired power plants spew tons of chemicals in the air. Our cleaning supplies, plastics, and many other household items contain dozens of harsh chemicals.
Besides early detection, there seem to be two approaches to fighting cancer. First, there’s the vaccine approach, which aims to boost the patient’s immune system by triggering the production of special cells that kill cancer cells and prevent relapses. The United States Food and Drug Administration has approved two types of vaccines to prevent cancer: vaccines against the hepatitis B virus, which can cause liver cancer, and vaccines against the virus that causes cervical cancer. Will we find a universal vaccine that will do the same for cancer as vaccines did for polio and smallpox?
The second approach aims at cutting the blood supply to tumors. Drugs like Avastin inhibit the formation of new blood vessels that feed tumors. This is a simpler method than the vaccine idea, which involves a lot of very complex biological processes that are not thoroughly understood.
I queried several doctors about the outlook for cancer treatment, and they all said basically the same thing. They think we’re making great progress in treating all types of cancers, some more than others. They speculate we’ll have a cure for most cancers in twenty to fifty years. We’ll have techniques and devices that will spot even a few cancer cells, and we’ll have the tools to go after those cells. The hardest cancers will be the kinds that, like AIDS, compromise or attack the immune system. And even present treatments using surgery, radiation, and chemotherapy are getting better.
The tallest person on record is Robert Wadlow from Illinois, who died in 1940 at the age of twenty-two. He stood eight feet, eleven inches tall. At the present time, there is a thirty-three-year-old man living in the Ukraine who is eight feet, five and a half inches tall. But he grew one foot fairly recently, so he might surpass Wadlow. Both men owe their extreme height to a condition called acromegalic gigantism. Height is determined by genes, hormones, and nutrition. We humans stop getting much taller soon after puberty. Growth of bones is limited by sex hormones, which tell the ends of bones to stop growing. The average age we are at this stage differs across genders: For boys, it is about age eighteen, and for girls, it is about age sixteen. Both Wadlow and the Ukrainian, Leonid Stadnyk, had a tumor on the pituitary gland. The tumor destroys cells in the pituitary gland that stimulate the release of sex hormones. So the bones never get the signal to stop growing.
Marfan syndrome is a genetic disorder of the connective tissue. People with Marfan syndrome tend to be tall, with long limbs and long fingers. Abraham Lincoln is believed to have suffered from Marfan syndrome.
Medical experts figure that it would be hard for a nine-foot person to live very long. There would be very high blood pressure in the legs, which would lead to burst blood vessels and varicose ulcers. It was an infected ulcer, for example, that killed Wadlow.
Even with modern antibiotics to control infections, an extreme height puts a big strain on the heart. It’s a huge job for the heart to pump blood up a height of seven or eight feet.
Some teens go through growth spurts. This growth starts on the outside of the body and works in. Hands and feet are the first to expand; needing new shoes is a sign of a growth spurt. Next, arms and legs grow longer. Then the spine lengthens. Finally, the chest and shoulders widen on boys, the hips and pelvis on girls.
Can a concerned young person increase their height? Yes, to some small extent. A diet rich in fruits and vegetables, cereals, and meat is helpful. Plenty of sleep is crucial. Lack of sleep limits growth hormones. And there are some specific stretching exercises that one can do.
Can human growth hormones (HGH) make a person taller? Yes, if taken during the early years, when a person is growing. But it is tricky, and there are a lot of fraudulent promoters out there. HGH should be prescribed only by a medical specialist.
There are advantages to being tall. Short people are at a disadvantage when seeking jobs. Women are said to be generally more attracted to taller men.
Of the twenty-eight presidential elections from 1900 to 2011, the taller of the two candidates has won eighteen times, the shorter candidate has been elected eight times, and two have been the same height.
I think this has probably happened to most of us at one time or another. The most common type of muscle spasm seems to be leg cramps, which are, like all muscle cramps, contractions of the muscles. According to several reliable medical websites, the usual causes are dehydration, use of diuretics, overuse of muscles from heavy exercise, muscle fatigue, stress or anxiety, and lack of vitamin C. Some low-carb diets, like the Atkins diet plan, lack vitamin C. Drinking too much coffee, a diuretic, can be a big causal factor.
Recommendations for relief include stretching and massaging the leg muscle to help the muscle relax. Putting weight on the “cramped” leg and bending the knee may help. A cold pack relaxes tense muscles (but keep a cloth between it and your skin). Later, apply a warm towel or heating pad if there is pain or tenderness.
Restless legs syndrome is a neurological disorder characterized by an irresistible urge to move one’s body to stop uncomfortable or odd sensations. It most commonly affects the legs. Movement is the most common activity that brings relief.
A good website for basic concerns about health issues is www.my.webmd.com. It suggests seeing a doctor if muscle cramps or spasms persist.
The title “fastest man alive” did belong to Jamaican sprinter Asafa Powell. Powell was clocked at 9.77 seconds in the hundred-meter dash on June 14, 2005, at the Olympic Stadium in Athens. The Athens track is said to be one of the fastest in the world. In May 2008, Powell did the hundred meters in 9.74 seconds. If my calculations are correct, that comes out to about 23 mph.
Today the title of “fastest man in the world” is assigned to Jamaican Usain Bolt, who ran the hundred-meter dash in a time of 9.58 seconds in Berlin in 2009.
The American Justin Gatlin won gold at the 2004 Summer Olympics in Athens with a time of 9.85 seconds in the hundred-meter run, currently making him the third fastest man of all time. Gatlin would jump over fire hydrants while growing up in Brooklyn, New York. The amazing University of Tennessee track star broke many short-distance records in the 2005 season.
The “fastest woman alive” was Florence Griffith Joyner, who did the hundred-meter dash in 10.49 seconds in 1988. Joyner died in 1998 of suffocation from an apparent epileptic seizure. She was only thirty-eight years old.
The hundred-meter race is an ideal distance to establish a human’s top speed. Any longer distance would have the sprinter not running their maximum speed for the entire race. Any shorter distance would mean that a considerable part of the run is used just to get up to top speed.
These speeds are records for humans moving unassisted. The fastest humans alive are the three astronauts who returned from the moon on the Apollo 10 mission on May 26, 1969. Gene Cernan, Thomas Stafford, and John Young were moving at roughly 11,000 meters per second, or about 25,000 mph, just prior to their entry into the Earth’s atmosphere.
We often call these images afterimages or retinal fatigue images. And they’re a lot of fun to look at.
The generally accepted theory for why they appear is the retinal fatigue idea. There are three types of color receptors, or color-sensitive cells, that make up the cones on the retina of the eye. Some of these cells are sensitive to red color, some to green color, and some to blue color. Red, green, and blue are the primary colors when it comes to light (see question 37).
When we stare at any particular color for too long, the receptors, or cells, for those colors get “tired,” or fatigued, and do not work very well. We may not notice this until we look at a white background, which reflects light of all colors. The receptors that are tired do not transmit the color they are sensitive to along to our brain, so we only see the other colors, which combine to form the complementary, or inverse, color of the image. For example, if we stare at a green-colored object for thirty seconds or more, then look away at a white screen or white sheet of paper, we see a magenta, or purple-like, color, a combination of red and blue. If we look at something blue for a period of time, then glance at a white page, we see a yellow image. Yellow is the complement, or opposite, of blue.
There are some excellent websites that have afterimages and a good explanation of how they work. This is an excellent one: http://www.colorcube.com/illusions/aftrimge.htm. The most famous of the retinal fatigue images is the reverse American flag. Stare at the green, black, and yellow colors for a time. Then fix your gaze on a white sheet of paper, and the familiar red, white, and blue Old Glory appears.
Doctors and nurses in the hospital operating room wear scrubs that are blue-green, or cyan, in color. The doctor might be looking at red blood for a long time and under bright lights. If the doctor looked up and saw an assistant’s white scrub suit, there would be a disturbing blue-green afterimage. But if the assistant’s clothes are already blue-green, the afterimage is barely noticeable.
I always considered eyesight, or vision, to be one of God’s greatest gifts. Then God threw in color for extra credit!
Because my field of expertise is the physical sciences, I like to consult experts when it comes to questions in the biological sciences. Tim Kortbein, a physical therapist I know at our local hospital, says that there is a definite relationship between weather changes and people’s complaints about their joints and muscles.
The barometric pressure drops as a storm or bad weather is approaching. Joints may not be able to adjust to the pressure change, and then the soft tissue and fluid around joints expand, irritating nerves and causing pain. This is especially true of any joints that are arthritic. Also, the metal that is in knee, ankle, or hip replacements can cause pain if the weather turns cold. This is particularly true for patients who have had recent implants or replacements. For the first few years, the bone is adapting and growing around any metal prosthesis. Bone activity is sensitive to weather and pressure changes.
If an injury is not rehabilitated properly, problems may show up later in life. An injury to a leg or ankle may cause a person to favor that leg. A change in walking style may then result in overuse and impairment. Muscles work in pairs. For example, the biceps in our upper arms contract while the triceps relax. If an injured muscle is not properly rehabilitated, a stronger muscle may overpower the weaker one it is paired with.
Sneezing is a reflex response that expels an irritant from the nose (see question 12). It involves numerous muscles in the face, throat, and chest. The sneeze reflex uses muscles that close the eyes as well. A reflex action is a series of reactions that are programmed in the body by the brain. This makes it nearly impossible to voluntarily keep our eyes open when we sneeze. However, for some people, it is possible to ward off a sneeze by pinching the end of their nose.
The speed of a sneeze was estimated to be, on average, 100 mph, or about the same as the best fastball in baseball. However, MythBusters Adam Savage and Jamie Hyneman conducted a scientific probe of the venerable sneeze and found speeds of 35 mph for Adam and 39 mph for Jamie. That is far less than the previously accepted 100 mph. In addition, the sneeze traveled seventeen feet for Adam and thirteen feet for Jamie, considerably less than what conventional wisdom would expect.
Thomas Edison came up with the idea of movies from watching someone sneeze in 1888. He was studying the successful motion-sequence of still photographic experiments of Eadweard Muybridge and Etienne-Jules Marey. In 1889, Edison was viewing sequential pictures and guessed that if you viewed them rapidly in sequence, you might be able to make a moving picture.
Edison assigned the task to one of his most capable assistants, a young Englishman by the name of W. K. L. Dickson. In January 1894, Dickson produced a short film entitled The Edison Kinetoscopic Record of a Sneeze. The person doing the sneezing was another Edison employee, Fred Ott. The film piece was then deposited in the Library of Congress and is the earliest surviving copyrighted motion picture.
The short answer is: no! Tanning is a response to injury and is nature’s way of protecting us, so tanning booths work by causing injury to the skin. Tanning occurs when enzymes stimulate cells in the skin to make melanin, a dark pigment that absorbs ultraviolet (UV) light (see question 24). The job of melanin is to protect the DNA in the lower layers of skin cells. Melanin is a UV absorbent and acts as an antioxidant.
UV light from the Sun or a tanning booth penetrates the upper layers of the skin and damages the DNA inside skin cells. Repair enzymes are sent to get rid of the injured DNA and aid in making new DNA. Sometimes, because of the damage, these repair efforts go wrong and create cancer.
There are some additional drawbacks to tanning, whether in tanning booths or under the Sun. Chronic exposure causes a change in the skin’s texture by damaging the connective tissue, causing the skin to become leathery and wrinkled. Tanning can bring on age spots, and it can damage the body’s immune system. Exposure in tanning booths can even produce cataracts.
Experts advise that we don’t spend any time in tanning booths—which the World Health Organization calls a “known human carcinogen”—but some sunlight is good for us, even necessary. Sunlight stimulates the production of vitamin D; tanning booths, on the other hand, do little for our vitamin D levels, because they expose us mainly to UVA light, a type of ultraviolet light, and it’s UVB that stimulates vitamin D. Lack of vitamin D causes rickets in children, which produces soft and malformed bones.
The clinician pumps up the blood pressure cuff with air using a hollow squeeze bulb that allows the air to flow in only one direction. A tiny check valve prevents air from coming back into the bulb. The inflated cuff cuts off the flow of blood in the arteries and veins. Then the doctor or nurse slowly reduces the pressure in the cuff. At the point where the blood can barely squeeze through the compressed blood vessels, this flow is turbulent. The chaotic movement of blood through the blood vessels creates noise.
This is what the health practitioner listens for. When they first hear the turbulent noise, they take the higher blood pressure reading (the systolic pressure). When that turbulent noise disappears, it means that the smooth flow of blood has returned in the veins and arteries, and the practitioner notes the lower second reading (the diastolic pressure).
Blood pressure is the pressure, or push, of the blood against the blood vessel walls. It is one of the four vital signs, the other three being body temperature, breathing (respiratory) rate, and pulse rate (heart rate).
The common device used to take blood pressure is known by a massive six-syllable word: sphygmomanometer. The numbers used for blood pressure originally represented how high, in millimeters, the pressure exerted by the pumped air could push a column of mercury (in a tube of a standard diameter) upward; the unit of measurement for blood pressure is millimeters of mercury, or mm Hg. Today, most sphygmomanometers do not use mercury but instead use an aneroid (without liquid) or electronic device.
Blood flow in our body is somewhat like the flow of water in the pipes of our house. There are gauges that measure the pressure of that water against the pipe walls. The “plumbing” of the human circulatory blood system can be over one hundred thousand miles long, depending on the person’s size.
For many years, doctors considered a normal blood pressure to be about 120/80, which can be stated as “one-twenty over eighty.” The first number, 120, is the systolic reading, which shows the peak pressure in the arteries, when the ventricles are just starting to contract, pushing blood to all parts of the body (see question 18). The 80 number represents the diastolic pressure, the minimum pressure in the arteries, when the ventricles are relaxed and filling up with blood.
In our example above, if a mercury-filled tube was placed against the artery wall, the blood pressure would push that column of mercury up 120 mm, or nearly five inches, when the heart is working hard, and 80 mm, or a bit over three inches, when the heart relaxes.
Various factors affect blood pressure, including age, sex, height, exercise, sleep, diet (particularly sodium), disease, being overweight or obese, drugs, alcohol, smoking, emotional reactions, stress, digestion, and time of day. Most people have a higher reading in the afternoon and a lower one at night. In children, blood pressure varies with height. As we get older, the systolic pressure rises and the diastolic falls some. Many people’s blood pressure is sensitive to salt and other sources of sodium in their diet. For these people, sodium in the food they eat tends to raise their blood pressure and potassium helps lower it. You can see how much sodium is in a serving of a packaged food by looking at the Nutrition Facts label.
Personally, two things can really spike my blood pressure upward. The first is filling in Line 76 on the standard IRS 1040 form, “Amount you owe.” The second is seeing, in my rearview mirror, those alternating flashing red and blue lights on a car tailing very close behind.
There is a saying that goes: “The joke was so funny it caused him to have nose cola.” Excessive jocularity can cause water, milk, or soda to come out the nose.
Food and drink should go down the esophagus and into the stomach. Air should go down the trachea, then into the branching bronchial tubes, and end up in the lungs. But those two tubes, the trachea and the esophagus, are quite close to each other. So the drink can go down the trachea and bronchial tubes—we say it goes “down the wrong pipe”—and then be expelled out the nose. Instead of being swallowed, the fluid goes up the nasal passages and out through the nostrils.
There is no real danger medically. Perhaps there is some social embarrassment for an adult. Absolutely no embarrassment for a preteen or teen boy!
The human body has safety devices that prevent food and drink going down the wrong way. There is a flap in the back of the throat called the epiglottis. The epiglottis covers the larynx when you swallow food. Sometimes, if a person is talking or laughing while swallowing food or drink, the epiglottis does not block the larynx completely and food enters the wrong pipe. It can spurt out the nose.
The larynx sits atop the trachea. The larynx contains the vocal cords that we need to speak and sing. These vocal cords close up and go into a spasm if food or fluid gets to them. As a final defense, if food or drink gets into the trachea or windpipe, you have a cough reflex that should expel any foreign matter. These three mechanisms can be dismantled by excessive alcohol, which will allow food and drink to get into the bronchial passages and cause death by asphyxiation.
What about a cow? If a cow laughed really hard, would milk come out her nose? The answer is no. It’s udderly impossible.
Answers vary from 640 to 850, depending on how you count them. Muscles make up the engine of the body by turning energy into motion. It is impossible to do almost anything without them: talking, eating, writing, running, and dancing are all done with muscles. In addition, we have muscles that act involuntarily for breathing and for keeping our heart beating.
Muscles are divided into three body systems. Skeletal muscles move the bones and the facial muscles. These muscles have striped, or striated, fibers and are called voluntary muscles because the human brain consciously controls them. These muscles are the ones that get injured in physical activity or sporting events. They make up about 47 percent of body mass in men and about 38 percent in women.
Smooth muscles are found in the stomach and intestinal walls, in vein and artery walls, and in other internal organs. These are involuntary muscles; we do not generally control them, so we don’t need to consciously think about them. Instead, they get their signals from the autonomic nervous system, which tells muscles like the secretory glands to pump hormones directly into the bloodstream and the digestive smooth muscles to push food through the intestines. These muscles are also located in the urethra, bladder, esophagus, and bronchi.
Cardiac muscles, or heart muscles, contain both striped and smooth muscle tissue, and they consist of a branched, continuous network of muscle fibers, with prominent bands crossing the fibers at various intervals. Purkinje fibers form the impulse-conducting system of the heart, and they’re totally involuntary, thank goodness. No need to “tell” the ticker to keep ticking.
Muscles come in different sizes, and some muscles work harder than others. The busiest muscles in the body are the ones that do the blinking for us. We blink 15,000 to 22,000 times every day, both voluntarily and involuntarily. The smallest muscle is the stapedius muscle, in the middle ear. The largest is the gluteus maximus, or buttock.
If we work our muscles too hard, the cells run out of oxygen. This starts a fermentation process that produces lactic acid. The buildup of lactic acid in the muscles causes soreness and stiffness.
Muscle exercise also affects bone growth. Ultrasound studies on major league pitchers indicate that their pitching arm’s bone is larger and stronger than their non-throwing arm’s by as much as 30 percent.
Muscle fibers are long cylinders compared to other cells in the body. Their job is to create contraction, and, when necessary, to relax. All muscle activity is electrical; the brain sends an electric signal to the muscle and tells it to contract. A little or a lot, depending on the nature of the signal.
Multiple sclerosis, or MS, is a disease in which these signals traveling along the nerve fibers are interrupted or distorted by scar tissue. Muscular dystrophy, or MD, is a loss of muscle mass. The muscle wastes away, getting weaker and weaker. MD is an inherited condition, passed down through families.
Blinking is a way of providing moisture to the eye. The average blink rate is ten to twenty times per minute. Blinking is involuntary, not something we consciously do. The blink lasts a fraction of a second; we rarely even realize it’s happening, and it is fast enough that it does not interfere with our vision. We all blink so often that we tend to ignore it altogether; we hardly ever notice blinking in other people.
Blinking is different from batting one’s eyes. Batting is opening and closing the eyes several times in rapid succession, usually deliberately.
During a blink, the upper eyelid comes down over the eyeball and creates suction across the eye to prevent it from drying out. Moisture, provided by tear glands through tiny ducts, flows over the surface of the eye. The eyelids have about twenty-five oil-producing glands, located between our eyelashes and not visible to the human eye, and this oil mixes with the water from the tear glands. So blinking provides water and oils for the eye, similar to a farmer irrigating crops.
Blinking also affords protection for our eyes. Blinking shields the eye from dust and debris, and our eyelids function as windshield wipers when a particle does come in contact with the eye. But the first line of defense is eyelashes. Those curved hairs are dust catchers that prevent dust in the air from hitting our eyeball. Eyelashes are common in the animal kingdom. You might have noticed that cows and horses have long eyelashes, and camels in the desert have extremely long eyelashes to protect their eyes from sand.
There is strong evidence that blinking is useful when we change focus. We may be looking into the distance, say, out the window. Then we shift our attention to something close, say, a computer keyboard. Blinking helps the eye to settle into a new point of focus. People have been observed to blink more often during changes in focus of their eyes.
From a research group in Japan comes evidence published in the The Proceedings of the National Academy of Sciences that blinking may help us gather our thoughts and focus our attention. They suggest that blinking provides something like a mental resting place that shuts off visual stimulation and refocuses our attention.
Rapid blinking may indicate a sign of nervousness in a person. There is some evidence that a person exhibiting rapid blinking may be hiding the truth or telling a lie.
There are some recognized disorders associated with excessive blinking. The cause could be the side effects of medication or some psychological unease. Other causes are fatigue, allergies, eyelid inflammation, Tourette’s syndrome and other tic disorders, brain tumors, and seizures. Chronic dry eyes can also bring on excessive blinking. Being outdoors in windy conditions can dry out the eyes in a hurry. This can occur when the water in tears evaporates faster than the oil layer in the tears. Advanced age, contact lens use, and certain medications are other common causes of dry eyes. People might find temporary relief by using eyedrops or artificial tears.
We’ve all been there: feeling stressed, scared, nervous, ashamed, or embarrassed. Any strong emotion can induce blushing. That includes hearing a flattering remark, making a speech, being the center of attention, or feeling self-conscious. Getting angry can bring on a blush, too. In every case, the face turns various shades of crimson.
Science doesn’t have all the answers about blushing. Medical people say that blushing is a result of both the “fight or flight” response and social behavior. “Fight or flight” is the theory that animals react to threats with a reaction of the nervous system that prepares the animal for fighting or fleeing.
Blushing in humans is triggered by social situations, not threats to health or life. Animals don’t blush. So even though some responses may be inherited traits from our distant past, blushing in humans is related to something animals don’t have, namely, a moral consciousness.
The body secretes more adrenaline as part of the sympathetic nervous system response. This system is involuntary; you don’t have to think about it. The pupils of the eye grow bigger, allowing you to take in more visual information. The capillaries that carry blood to the skin widen. There is increased blood flow to the neck and limbs. The heart rate increases, and breathing becomes faster. The blood vessels in the face dilate, opening to more blood flow, and the face reddens.
Blushing is more noticeable in people who have fair skin. Northern Europeans—Nordic, English, and German people—generally fall in this category.
There can be other reasons for a red face. People who suffer from hypertension may show a reddened complexion. And as the body heats up during exercises, it tries to cool down both by sweating and by sending more blood to the surface of the skin. Alcohol can cause arteries to widen, too. Some Asian populations don’t have the ability to break down alcohol in the liver. The toxic material enters the bloodstream and causes blushing.
Blond hair is common in infants and children. Babies are often born with blond hair even though their parents have dark hair. That blond hair turns darker with age so that blond-haired kids have dark or even black hair when they are in their teen years.
The chemical melanin gives hair its color. The more melanin, the darker the hair color (see question 24).
Hair color historically was tied to geographic areas. Hair color in southern Europe, North Africa, the Middle East, and the Americas was dark brown or black. In central Europe, lighter brown hair was common. Blond or yellow hair, and even red, was prevalent in northern Europe, Britain, and Ireland. The country of Lithuania has the highest percentage of people with blond hair. To this day, blond, or “fair,” hair is common in northern Europe: Norway, Finland, Sweden, Denmark, and the Netherlands. Very pale hair is known as “Nordic blond.” Blond hair in northern Europeans is also associated with eye color. Fair-haired people tend to have blue, green, or light brown eyes.
The Human Genome Project, completed in about 2003, sought to identify the approximately 20,000–25,000 genes in human DNA. The Project also determined the sequence of the three billion pairs of chemical bases that make up our DNA. This project turned up very strong evidence that two gene pairs and a few other specific chromosome regions control human hair color.
An allele is one member of a pair of genes that a person has. Each can be dominant or recessive. One gene pair is a dominant brown and a recessive blond. A brown-haired person can have either two brown alleles or one brown allele and one blond allele. This model explains why two brown-haired parents can have a blond child: Both parents have one of each allele, and the child received two recessive alleles, one from each parent. The other gene pair is a non-red/red pair.
But this still doesn’t explain why hair color changes as kids grow older. If genes can’t explain this, there may be some environmental factors involved. One such factor is strong sunlight, which tends to lighten hair as it washes the color out. Some kids who run around outside in the summer will have pale blondish hair by the end of summer, but the pigment returns as new hair grows in the wintertime. Their hair is back to its brown color by Christmas.
There’s still one more mystery: the spelling. While some people use “blond” and others use “blonde,” both are correct, although there’s a tendency to associate “blond” with males and “blonde” with females.
Well, I feel your pain. It happened to me, also. I was the only one in my class to wear glasses during second and third grade. Of course, there were only four kids in my class in that one-room country school in Wisconsin. After I had been wearing glasses for about eighteen months, a real stroke of good luck came to pass. I fell down on the ice at school, at the little frozen pond created when water filled in the home plate area of our softball field and the weather turned cold. It made a nice round skating area about eight feet across. We threw snow on the ice to make it a bit more slippery.
Too slippery for boy Scheckel: Down I went, and I shattered one of the glass lenses. These were real glasses, not the plastic lenses we have these days. After the obligatory scolding, my dad and mom took me to the eye doctor in La Crosse and had my vision retested. The doctor said I didn’t need glasses anymore! Perhaps there is a silver lining in home plate ice ponds.
That familiar eye chart was developed during the Civil War by Dutch ophthalmologist Herman Snellen. It’s still called a Snellen chart. If you can read the line that says 20 without glasses, you have normal vision, or 20/20 vision. You can read at 20 feet what everybody with normal vision can read at 20 feet. If you have 20/40 vision, you need to be 20 feet from what people with “normal” vision can read at 40 feet. That’s not too good.
Test and fighter pilot and sound-barrier breaker Chuck Yeager has 20/10 vision. He can read the letters on the line labeled 10 at a distance of 20 feet, while normal-visioned people need to be 10 feet from the chart. That is top-notch eyesight.
Most kids who need glasses are nearsighted, or myopic. Objects far away look fuzzy. Activities that involve their close-up vision, such as reading a book or looking at a computer screen, are OK. The corneas and lenses in their eyes focus the image in front of the retina, which is that light-sensitive layer of cells on the backs of the eyeballs.
The lenses needed to correct nearsightedness are generally concave, thinner in the middle of the lenses and thicker at the edges. It’s just the opposite for a farsighted, or hyperopic, person. The cornea and lens do not bend, or refract, the incoming light rays sufficiently and tend to focus them behind the retina. Farsighted people can see things clearly far away, but their close-up vision is not good. They typically need a convex lens, one that is thicker in the middle and thinner on the outside edges.
Astigmatism is another vision defect that might cause a person to wear glasses. The front surface of the eye, the cornea, is somewhat oval instead of being round. It bends entering light rays different amounts depending on the direction they come in from. A person with astigmatism has distorted vision. Lenses can be ground to correct for the astigmatic error. Astigmatism can also be corrected by laser surgery. The cornea is reshaped by removing bits of the cornea using a highly focused laser beam.
Two types of laser surgery are used to correct for refractive errors, including nearsightedness, farsightedness, and astigmatism: photoreflective keratectomy (PRK) and laser in situ keratomileusis (LASIK). PRK removes tissue from both the surface and inner layers of the cornea. LASIK surgery removes tissue only from an inner layer. In LASIK surgery, a section of the cornea surface is cut and folded back to expose the inner tissue. A laser removes the correct amount of tissue needed and the flap is placed back into position to heal.
There is one thing that all kids, and grown-ups, too, can do to protect their eyes: Wear UV-protection sunglasses when outside for any long period of time. Studies suggest you’ll greatly reduce your chances of getting cataracts later in life.
Sound is produced when air is moved by our vibrating vocal cords. The pitch, tone, or frequency (all the same thing) of our voice depends on several factors. A person with a bass voice has long vocal cords and lower pitch. One with a soprano voice has short vocal cords and higher pitch. Another factor is the configuration of the anatomy involved in producing our voices. Yet another factor is the gas that we breathe, normally a mixture of oxygen and nitrogen. So the way we sound is determined by a host of factors: the size and shape of our larynx, trachea, mouth, and nasal passages; the length of our vocal cords; and the density of the gas we breathe.
Helium has one-seventh the density of air. So sound travels much faster through helium than it does through air. As a matter of fact, sound moves about 1,100 feet per second through air but about 3,000 feet per second through helium.
The vibration rate of the vocal cords does not depend on the kind of gas that surrounds them. Helium does not make the vocal cords longer or shorter, nor does helium change their tension or stretch. It is the less-dense helium, which serves as the medium for the sound waves, flowing through the larynx that produces this Donald Duck effect. It changes the resonant frequency of the vocal tract, causing a faster vibration and a higher pitch.
Breathing helium from a balloon and producing the cartoon character Donald Duck sound has been going on since people started putting helium in birthday and party balloons. Just a word of caution: In 1996, a healthy thirteen-year-old boy inhaled helium gas directly from a pressurized tank. He just about died from a cerebral gas embolism when bubbles got into his bloodstream and traveled to his brain. Doctors got him into a hyperbaric chamber, the kind that is used by underwater divers who get the bends. He was lucky and made a complete recovery.
In February 2012, a fourteen-year-old eighth-grade girl in Oregon died from inhaling helium from a pressurized canister. The pressure in the tank sends helium with such force that the lungs are ruptured. So don’t put your mouth on the nozzle of a helium tank! Also, those helium tanks might have tiny particles of metal in them. And if those get in your lungs, they will stay there. Talk about your heavy metal!
Another gas, sulfur hexafluoride (SF6), is about five times denser than air and can make a person’s voice sound much lower, like the actor James Earl Jones’s voice.
Near the end of his life, Albert Einstein was asked for the secret of his success. He replied, “I never tired of asking simple questions. I ask them still.” At first glance, asking why our pupils are black looks like a simple question. But the answer can be quite complex.
The pupil is the opening in the center of the iris where light enters the lens, which then focuses it on the retina. No matter what color eyes we have, everyone has black pupils. The pupil is black because all the light that enters through the pupil is absorbed inside the eye and none of it is reflected.
Imagine the pupil to be colored, let’s say red. White light (sunlight, incandescent light, fluorescent light) consists of the seven ROY G BIV colors: red, orange, yellow, green, blue, indigo, and violet. The red pupil would reflect the red portion of light, which would not enter the eye. This would distort the color of everything we see. It would be like perpetually looking at the world through stained-glass windows. So, as it turns out, the color of the pupil must be black in order for us to see the spectrum of colors from red to violet.
Under normal lighting conditions, the diameter of the pupil is about four millimeters. (A millimeter is about the thickness of a dime.) The size can change from about three millimeters in bright light to about eight in dim light. The size of the pupil is responsible for depth of field, sometimes termed depth of focus, or the range of distances over which we can see objects in good focus. A small opening, or aperture, increases depth of field. That’s why we squint when we are having difficulty seeing something. In the language of camera buffs, we are “stopping down our eyes.”
A lot of people wonder about this. The answer is no. Our DNA contains the instructions for making us who we are. Identical twins have DNA that is almost indistinguishable, because they are formed from a single fertilized egg that splits into two after conception. But fingerprints are not the result of genetics alone. Identical twins have the same genetic makeup (genotype) and are very much alike, but there are subtle differences—enough that people, especially parents, can tell them apart. That’s because such characteristics as height, weight, body form, reflexes, metabolism, and behavior (phenotype) are determined by a person’s individual genes and by the interaction with nature. This is also the case with twins’ fingerprints.
It’s that age-old “nature versus nurture” question. How much of what we are as humans is the result of our genetic makeup (nature), and how much is determined by our interaction with the environment (nurture)? By environment, we’re talking about how you’re raised, your home situation, what you eat, how you sleep, your siblings, and the air you breathe—in short, everything and everyone around you.
Here’s where it gets really interesting. Fingerprints are one of those traits that are the result of development of the baby during pregnancy. Those factors include fetal blood pressure, nutrition, position in the womb, and how fast the fingers are growing by the end of the first trimester. The creation of the patterns of the fingerprint is caused by stresses in a sandwiched sheet of skin called the basal layer. The basal layer grows faster than surrounding layers, and as it does so, it buckles and folds in several directions, forming complex shapes. It’s a very random process.
The fingerprints of both identical twins are quite similar, but there are differences in the patterns of arches, whorls, and loops. These differences are caused by the random stresses in the womb—even the length of the umbilical cord has an influence. There are also differences between the fingers on any individual’s hand. Probably the most celebrated case was that of the Dionne quintuplets, born in Ontario, Canada, in 1934. The five identical (same DNA) girls all had different fingerprints and handprints.
It is worth adding that fraternal twins develop from two different eggs. Fraternal twins are no more closely related than ordinary siblings. They just happen to share the same growing space for nine months.
Iodine tablets—in the form of potassium iodide (KI)—protect the thyroid from cancer. The thyroid is the body organ most at risk from excessive amounts of radiation. The thyroid is a butterfly-shaped endocrine gland found in the neck near the Adam’s apple, lying against and around the larynx and trachea. It regulates metabolism, body temperature, physical growth rate, and brain development.
The thyroid uses iodine to make thyroid hormones, but it can’t distinguish between regular iodine and radioactive iodine, the isotope iodine-131 (I-131). The concept behind taking iodine tablets is to fill up the thyroid gland’s receptors with regular, good iodine from the tablets, and then they can’t take in much of the bad, radioactive iodine. Children and unborn babies are the most vulnerable, because the cells in their bodies are dividing much faster than those in adults, and people whose iodine levels are low are more likely to get thyroid cancer if they are exposed to radiation.
There are side effects from potassium iodide that can be serious, including damage to the salivary glands, allergic reactions, and really bad stomach upsets. Also, iodine pills do not prevent other cancers or protect other organs in the body.
Iodine pills have to be taken before or immediately after exposure to be effective. After the 1986 Chernobyl nuclear accident, authorities waited too long, over a week, before issuing iodine pills. They did more harm than good; radioactive iodine got locked in people’s thyroids. Radioactive iodine isn’t all bad, though; it is used to treat thyroid cancer and certain other thyroid disorders. However, patients must then take precautions to avoid exposing the people around them to it.
In some parts of the world, where iodine is lacking, the thyroid gland can become enlarged, giving the person a goiter. A goiter is an enlarged swelling of the thyroid and often appears as a large growth in the neck area. As youngsters in a one-room country school in the hill country of Wisconsin, my classmates and I were given a purple “goiter pill” every Friday. The soil around the Great Lakes region does not contain much iodine.
The Morton Salt Company started putting iodine in salt as early as 1924. These days edible salt is sprayed with potassium iodate for little more than one dollar per ton.
Another well-known case of widespread radiation exposure affected children born in the 1950s and early 1960s, who have elevated levels of strontium-90 (Sr-90) in their bones and teeth. The United States and the Soviet Union were running nuclear bomb tests in that period; together, they tested 422 nuclear bombs in the atmosphere. Much of that radioactive material went high in the atmosphere, circling the Earth several times via the jet stream and finally settling down in fields. Cows ate the grass, kids drank the milk, and the Sr-90 settled in their bones and teeth. Strontium is just below calcium in the periodic table, and Sr-90 gets deposited in the same places in the body; it can cause bone and bone marrow cancer and leukemia. Thankfully, the 1963 Partial Nuclear Test Ban Treaty put an end to most atmospheric bomb tests.
An autopsy is a medical procedure to determine the cause and manner of a person’s death or to evaluate disease or injury. It is a medical examination of a dead body by a medical examiner or forensic pathologist.
An autopsy is performed when foul play is suspected and in cases of poisoning or drowning. Homicides, suicides, drug overdoses, and cases of sudden infant death syndrome (SIDS) are all candidates for an autopsy. Autopsies are also performed when a medical condition has not been previously diagnosed, for research purposes, or for cases where cause of death could affect insurance settlements or legal matters.
Most autopsies are performed by a forensic pathologist. The body arrives at the medical examiner’s office or hospital in a body bag or a sterile evidence sheet and is refrigerated if the autopsy is not performed immediately. Every step of the autopsy is documented with notes, photographs, and a voice recorder. The external surfaces of the body are examined, and the body is weighed and sometimes X-rayed.
Examination of internal organs starts with a large, deep, Y-shaped cut from shoulder to shoulder meeting at the breastbone and extending all the way down the length of the torso. The examiner then peels back the skin, muscle, and soft tissue and makes two cuts through the bone, one on each side of the rib cage. They can now remove the front of the rib cage, exposing all the internal organs. Next the examiner makes cuts to detach the larynx, bladder, rectum, and vertebral column. They can now remove nearly the entire organ set and examine the organs one at a time. The examiner can weigh and dissect various organs and prepare tissue samples for examination. The brain can be cut free of the spinal cord, removed, and examined separately.
An autopsy takes three to six hours, and throughout the entire process, the medical examiner is looking for signs of trauma or other indications of cause of death. When the autopsy is done, the examiner puts the organs back into the body or has them incinerated, replaces the rib cage, closes and sews up the chest flap, and replaces the top of the skull and sews up the scalp to keep it in place.
An autopsy does not prevent an open-casket funeral if the examiner performs what is called a cosmetic autopsy. Family members can request an autopsy, but they have to pay for it. The results can affect insurance settlements or serve as evidence in a legal case.
According to the office of my local medical examiner, my county, Monroe County, sends an average of seven bodies per year to the state capital, Madison, to have autopsies performed. The cost to the county for each autopsy is about thirteen hundred dollars. The decision to have an autopsy performed is made by the medical examiner, with input from the police department and district attorney’s office.
When President Kennedy was assassinated in 1963, federal agents took control of the body and the investigation. A nonforensic pathologist did the examination of the deceased president, which sparked controversy. Some claim the autopsy was botched. The law now mandates that a certified pathologist from the Armed Forces Institute of Pathology do examinations in federal investigations.