Many of our bodies’ major organs and muscles are regulated by the autonomic nervous system (ANS). In most cases, the ANS functions involuntarily: Our blood vessels narrow or our heart rates increase, for example, to help us respond to our environment. The system works without our conscious effort or, in many cases, even our awareness.

The ANS regulates muscles in the skin, eyes, heart, lungs, and stomach. It also controls the intestines, salivary glands, secretion of insulin, urinary function, and sexual arousal. The autonomic nervous system’s main goal is to maintain homeostasis, or proper balance, in the body through two main components: the sympathetic nervous system and the parasympathetic nervous system.

During periods of perceived danger or emergency, the sympathetic nervous system helps our bodies exhibit a fight-or-flight response. When faced with a threat—either physical or emotional—the brain responds to protect the body from danger: Blood vessels constrict to divert bloodflow away from the gastrointestinal (GI) tract and skin. Pupils dilate, letting more light enter the eyes. Lungs open up, allowing for greater oxygen exchange.

Conversely, the parasympathetic nervous system reverses many of these functions during calmer times. This allows us to rest comfortably, breathe easier, and digest food, absorbing more nutrients thanks to greater bloodflow to the GI tract. The parasympathetic nervous system is also involved in producing erections in males.

ANS problems include erectile dysfunction, excessive dizziness, incontinence, and inability to sweat. These disorders may arise with age or can be caused by an illness like diabetes. In such cases, treatment of the underlying medical issue may alleviate the disorder. If not, drugs are available to treat the symptoms of many autonomic disorders.

ADDITIONAL FACTS

  1. Some people can be trained to control functions of the ANS, such as heart rate or blood pressure, through practices such as meditation and biofeedback.
  2. The ANS is made up of neurons in the lower brain stem, in the brain’s medulla oblongata. If the central nervous system is damaged above that level, involuntary processes such as cardiovascular, digestive, and respiratory functions will continue, and life, although possibly in a vegetative state, can be sustained.
  3. When parts of the ANS stop functioning involuntarily, disorders such as decreased sweating, urinary retention, constipation, and erectile dysfunction can occur.