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21Anatomy and Physiology
ANSWERS
1. A Aneurysms are almost always located in the subarachnoid space, and are the most common cause. Choices C and D result in intracerebral hemorrhage (ICH), not subarachnoid hemorrhage (SAH), and choice B is a risk for ischemic stroke, not hemorrhagic stroke.
2. B The tentorium is also called the tentorium cerebelli, and means “tent of the cerebellum,” so picture it as a tent over the cerebellum, separating it from the cerebrum. The corpus callosum is a band of fibers that connects the two hemispheres; the falx is a dural fold that separates the two hemispheres; and the posterior fossa is the space where the brainstem and cerebellum lie.
3. D There are three layers of the meninges, the membrane covering the brain. The outermost layer is the dura mater, the middle layer is the arachnoid mater, and the innermost layer is the pia mater. There is no such thing as a central mater.
4. B The motor strip is located at the back of the frontal lobe. Wernicke’s area is located at the junction of the temporal and parietal lobes; the sensory strip—although it lies right next to the motor strip—is located at the front of the parietal lobe; the globus pallidus is in the basal ganglia, a subcortical structure.
5. 22A The postcentral gyrus is where the sensory strip lies—in the parietal lobe.
6. D The homunculus comes from the a 16th century alchemist’s description of a “little man” and this term has been used to describe the pattern of the motor and sensory control of the body.
7. A The thalamus relays auditory, somatosensory, visual, and gustatory signals between the cortex and the brainstem structures.
8. C The thalamus, hypothalamus, and pineal gland are collectively referred to as the diencephalon, which relays sensory information among brain regions and controls many autonomic functions of the peripheral nervous system.
9. C The temporal lobe is where Wernicke’s area is. It is responsible for receptive speech. Someone with damage to this area might have trouble understanding spoken or written language.
10. A The medulla oblongata is sometimes called the extension of the spinal cord within the skull. It controls heart rate and respiration; without its proper function, we cannot survive.
11. D The cerebellum is responsible for coordination and balance. When damaged, it can produce symptoms that have been mistaken for inebriation.
12. C Atrial fibrillation is a common cause of stroke because it can result in clots forming in the “quivering” atria; these clots can flow through to the cerebral circulation. Endocarditis can produce emboli, but the tricuspid valve is located in the right side of the heart, and any emboli formed there would flow to the pulmonary system, not to the cerebral circulation.
13. A The middle cerebral artery is connected to the circle of Willis, but is not considered to be part of it. The components of the circle of Willis are the internal carotid arteries, the anterior cerebral arteries, the anterior communicating artery, the posterior cerebral arteries, and the posterior communicating arteries.
14. C Collateral circulation refers to the “detoured” circulation via small vessels that circumvent a blocked larger vessel.
15. 23A The vertebral arteries connect the subclavian arteries to the posterior brain via the basilar artery.
16. D A deep vein thrombosis (DVT), if it becomes mobile, will flow into the right side of the heart via the vena cava. Blood from the right atria passes through the right ventricle, and flows out the pulmonary artery to the lungs, so most DVTs cause pulmonary embolus (PE). A patent foramen ovale (PFO) is an opening between the two atria. If this is present, the DVT can enter the right atrium and pass through the PFO into the left atrium, then through the left ventricle and out the aorta where it can get into the carotid circulation and into the cerebral circulation causing a stroke.
17. C The frontal lobe is responsible for many things—motor function, problem solving, spontaneity, memory, language, initiation, judgment, impulse control, and social and sexual behavior. Damage to the frontal lobe can result in inappropriate behavior, often sexual in nature.
18. A Middle cerebral artery (MCA) syndrome is characterized by motor and sensory loss in the face, arm, and, to a lesser degree, the leg, on the contralateral (opposite) side of the infarct.
19. A Lacunar syndromes are small infarcts of territories supplied by a penetrating artery branch of one of the major cerebral arteries. The area involved is small with finite impact on function. Pure motor syndromes produce only motor symptoms; pure sensory syndromes produce only sensory symptoms; and dysarthria–clumsy hand syndromes produce dysarthria and mild hand weakness. There is no such thing as a dysconjugate gaze syndrome.
20. C Intraparenchymal hemorrhage refers to blood within the brain or parenchymal tissue. Intracerebral hemorrhage refers to the same thing, thus is synonymous with intraparenchymal hemorrhage. Intradural hemorrhage is between the layers of the meninges, so not within the brain tissue; subarachnoid hemorrhage is under (sub) the arachnoid mater, between the arachnoid mater and the pia mater; intraventricular hemorrhage is blood in the ventricles, which may have come from either a subarachnoid hemorrhage or an intracerebral hemorrhage.
21. A The medulla is the lowest portion of the brainstem and controls respiration, and without its proper function, we cannot survive.
22. 24B The pons is located between the midbrain and medulla and serves as a communication and coordination center between the cerebrum and the cerebellum. Damage results in paralysis in the body and most of the facial muscles, but consciousness remains and the ability to perform certain eye movements is preserved.
23. C Broca’s area controls motor speech, so damage would result in an inability to speak in meaningful ways, or to use words to express your thoughts correctly.
24. D Intracerebral hemorrhage is most commonly caused by arterial rupture due to hypertension; aneurysms are most commonly found in the subarachnoid space, so rupture would result in subarachnoid hemorrhage.
25. A The parietal lobe is responsible for proprioception, the interpretation of the position of the body within its environment. Right parietal lobe damage can result in extinction, which is the inability to be aware of the contralateral side of the body in relation to the environment.
26. B Watershed infarct refers to stroke in the watershed territory—the space between two adjacent cerebral arteries—which is supplied by tiny penetrating vessels that are the first to collapse in the setting of hypoperfusion.
27. A The cerebral cortex is comprised of gray matter. There is no such thing as gray matter tracts, there are only white matter tracts.
28. B The corpus callosum is a band of white matter fibers that connects the left and right cerebral hemispheres.
29. C The tunica intima is the innermost layer of the arterial blood vessels. Its surface becomes roughened in the setting of uncontrolled hypertension and uncontrolled diabetes, resulting in the vicious cycle of platelet aggregation as the platelets attempt to smooth out the roughened areas. As long as the risk factor remains, the cycle continues and atherosclerosis and arteriosclerosis develop.
30. A AVMs are direct connections between arteries and veins that are not normal in human anatomy. The normal blood flow path is from arteries to arterioles to capillaries to venules, and finally to veins. Arteries have 2625muscular walls to handle the pulsing blood as it is pumped from the heart, but veins do not have muscular walls. Therefore if arterial blood flows directly into a vein via an AVM, the veins are likely to rupture under the pressure.
31. D Venous sinus thrombosis is the presence of a clot in the venous sinuses, blocking drainage from the brain. Congestion results in infarction, and often petechial hemorrhage.
32. C The blood–brain barrier, when intact, protects against influx of inflammatory cells. When disrupted, this protective mechanism may be incapacitated, resulting in edema and possible hemorrhagic transformation.
33. D Carotid dissection is the tearing of the intima of the carotid artery. Commonly, tiny clots form along the torn, rough edges of the tear. As they break off and migrate up to the brain, multiple tiny infarcts can occur, and because each carotid supplies only one side of the brain, dissection would result in infarcts on only one side. In vertebral dissection, the clots that break off and migrate would be joined in the basilar artery, which does not supply the hemispheres—it supplies the posterior brain. Binswanger’s disease is a condition of insufficient blood supply to the subcortical tissue, not the hemispheres.
34. D At cerebral blood flow values of less than 10 mL/100 g/min, irreversible damage occurs as cellular membrane integrity is lost, calcium flows freely into the cell, and neuronal cell death occurs (Alexander, 2013, p. 19).
35. A Under conditions of hyperthermia, metabolic needs increase as individual cells attempt to maintain ionic balance (Alexander, 2013, p. 23).
36. C In up to half of the cases of intracerebral hemorrhage, blood spreads into the ventricles where clots can obstruct the internal ventricular system, resulting in hydrocephalus. Research evidence indicates some benefit from infusing tissue plasminogen activator (tPA) into the ventricles to dissolve the clots.
Reference
Alexander, S. (Ed.). (2013). Evidence-based nursing care for stroke and neurovascular conditions. Ames, IA: Wiley-Blackwell.