Usmle Step 1 Qs (8)

2.

Gary is a 35-year-old man who was previously healthy until one day, when he noticed that his right leg was weak. As the day progressed, he found that he was dragging the leg behind him when he walked, and he finally asked a friend to drive him home from work because he was unable to lift his right foot up enough to place it on the gas peddle. He also noticed that his left leg felt a little bit numb. Finally, his wife convinced him to go to the emergency room of his local hospital. When Gary arrived at the emergency room, he was having a great deal of difficulty walking. The physician who examined him asked him when this began, and when Gary thought about it in more depth, he realized that perhaps this had started slowly several days before, and he had ignored the symptoms. Gary's language function, cranial nerves, and motor and sensory examinations of his arms were within normal limits. When the physician examined Gary's right leg, it was markedly weak, with very brisk reflexes in the knee and ankle. Vibration and position sense in the right leg were absent. Pain and temperature testing were normal in the right leg, but these sensations were absent on the left leg and abdomen to the level of his umbilicus. Reflexes in the left leg were normal, but when the physician scratched the lateral portion of the plantar surface on the bottom side of Gary's right foot, the great toe moved up. The remainder of Gary's examination was normal. The upward movement of Gary's toe when the plantar surface of his foot was scratched is indicative of a lesion in which portion of the nervous system?

UMN
LMN
Peripheral nerves
Muscles
Sural nerve

Correct Answer

A. UMN

Explanation

A positive Babinski's sign, or dorsiflexion of the great toe when the lateral portion of the plantar surface of the foot is scratched, is a sign of corticospinal tract dysfunction, a tract consisting of UMNs. Peripheral nerve (including the sural nerve) lesions are LMN lesions.

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3.

A 56-year-old woman experiences a loss of taste affecting the front of her tongue and the ability to smile as a result of an infection. Which of the following cranial nerve is most immediately affected?

Nerve V
Nerve VI
Nerve VII
Nerve IX
Nerve X

Correct Answer

A. Nerve VII

Explanation

Taste associated with the anterior two-thirds of the tongue is mediated by the facial (cranial nerve VII) nerve. The geniculate ganglion contains the cell bodies associated with the sensory (gustatory) component of the seventh nerve. The somatic motor component of the seventh nerve mediates the muscles of facial expression. Thus, the sensory and motor components of the seventh nerve affected in this individual can be characterized as special visceral afferent (because this afferent contains chemoreceptors) and special visceral efferent (because the motor component innervates skeletal muscle and is derived from a branchial arch), respectively.

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4.

Gary is a 35-year-old man who was previously healthy until one day, when he noticed that his right leg was weak. As the day progressed, he found that he was dragging the leg behind him when he walked, and he finally asked a friend to drive him home from work because he was unable to lift his right foot up enough to place it on the gas peddle. He also noticed that his left leg felt a little bit numb. Finally, his wife convinced him to go to the emergency room of his local hospital. When Gary arrived at the emergency room, he was having a great deal of difficulty walking. The physician who examined him asked him when this began, and when Gary thought about it in more depth, he realized that perhaps this had started slowly several days before, and he had ignored the symptoms. Gary''s language function, cranial nerves, and motor and sensory examinations of his arms were within normal limits. When the physician examined Gary''s right leg, it was markedly weak, with very brisk reflexes in the knee and ankle. Vibration and position sense in the right leg were absent. Pain and temperature testing were normal in the right leg, but these sensations were absent on the left leg and abdomen to the level of his umbilicus. Reflexes in the left leg were normal, but when the physician scratched the lateral portion of the plantar surface on the bottom side of Gary''s right foot, the great toe moved up. The remainder of Gary''s examination was normal. Why is Gary''s right leg weak?

There is muscle damage in the right leg
There is damage in his left frontal lobe
There is damage to the right corticospinal tract
The dorsal root is damaged
There is damage to the right femoral nerve

Correct Answer

A. There is damage to the right corticospinal tract

Explanation

The corticospinal tract mediates voluntary motor function. The fibers cross in the medullary pyramids, thus lesions below this structure cause ipsilateral weakness. The reflexes are brisk, since in a UMN lesion, there is a loss of inhibition to spinal reflexes. Muscle, dorsal root, and femoral nerve damage are all examples of lesions distal to the spinal cord. A frontal lobe lesion would not cause a sensory or motor level, and would probably cause problems more proximally, such as slurred speech.

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5.

Audrey is a 45-year-old woman who was brought to her local hospital's emergency room by her husband because of several days of progressive weakness and numbness in her arms and legs. Her symptoms had begun with tingling in her toes, which she assumed to be her feet "falling asleep." However, this feeling did not disappear, and she began to feel numb, first in her toes on both feet, then ascending to her calves and knees. Two days later, Audrey began to feel numb in her fingertips, and had difficulty lifting her legs. When she finally was unable to climb the stairs of her house because of her leg weakness, difficulty gripping the banister, and shortness of breath, her husband urged her to go to the emergency room. The neurologist who examined Audrey in the emergency room noticed that she was short of breath while sitting in bed. He asked the respiratory therapist to measure her vital capacity (the greatest volume of air that can be exhaled from the lungs after a maximal inspiration), and the value for this was far lower than was expected for her age and weight. Her neurologic examination showed that her arms and legs were very weak, so that she had difficulty lifting them against gravity. She was unable to feel a pin or a vibrating tuning fork at all on her legs and below her elbows, but was able to feel the pin on her upper chest. The neurologist could not elicit any reflexes from her ankles or knees. He subsequently advised the emergency room staff that Audrey needed to have a spinal tap and be admitted to the intensive care unit immediately. The absent reflexes are a sign of a lesion of which portion of the nervous system?

The frontal lobe
The dorsal horn of the spinal cord or any point distal to this structure
The brainstem
The cervical corticospinal tract
Any point that is proximal to the upper cervical spinal cord

Correct Answer

A. The dorsal horn of the spinal cord or any point distal to this structure

Explanation

The reflexes are lost because the LMNs, which are affected by this process, are unable to participate in the reflex arc necessary for a knee or ankle jerk to take place. These LMNs originate with stretch receptors in the tendons. Answers a, c, d, and e are all examples of UMN lesions, usually characterized by hyperactive reflexes.

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6.

Epileptiform activity is believed to include the activation of which of the following

GABA receptors
Glutamate receptors
Nicotinic receptors
Serotonin receptors
Glycine receptors

Correct Answer

A. Glutamate receptors

Explanation

Excitatory amino acids and, in particular, the glutamate family of compounds have long been thought to play an important role in epileptiform activity. Epileptiform activity typically includes AMPA-receptor activation. However, as the seizure becomes more intense, there is increased involvement of NMDA receptors. This is evidenced by the facts that NMDA antagonists can reduce the intensity and length of the seizure activity and that, following removal of human epileptic hippocampal tissue, there is an up-regulation of both AMPA and NMDA receptors. Metabotropic glutamate receptors have been shown to be present in the retina but have not yet been demonstrated to be present in regions of the brain that are typically epileptogenic. GABA and glycine are inhibitory transmitters; therefore, seizures would logically block such receptor activation. There has been no substantive evidence concerning the role of cortical nicotinic receptors in epilepsy.

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7.

A person is told that he has astigmatism. To correct this defect, the optometrist prescribes which of the following lenses

Cylindrical lens because the cornea or lens is oblong
Concave lens because the eyeball is too long
Convex lens because the lens is too short
Neutral lens because the eyeball is normal but the cornea is too thin
Concave lens because the cornea is opaque

Correct Answer

A. Cylindrical lens because the cornea or lens is oblong

Explanation

In astigmatism, the shapes of the cornea and possibly the lens become oblong, resulting in differences in the curvature of the lens along the long and short axes. Thus, astigmatism is corrected with a cylindrical lens.

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8.

Which of the following enzymes is directly responsible for the degradation of norepinephrine

Tryptophan hydroxylase
Tyrosine hydroxylase
Dopamine beta-hydroxylase
Catechol-O-methyltransferase
Choline acetyltransferase

Correct Answer

A. Catechol-O-methyltransferase

Explanation

Tryptophan hydroxylase, tyrosine hydroxylase, and choline acetyltransferase are enzymes that are critical for the biosynthesis of serotonin, catecholamines, and ACh, respectively. Dopamine -hydroxylase converts dopamine to norepinephrine. Catechol-O-methyltransferase and monoamine oxidase are critical for the metabolic degradation of catecholamines

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9.

The CT scan below reveals that the patient has a glioma (T) on the right side of the brain. It is likely that the patient has sustained which of the following?

A UMN paralysis of the left side
Dyskinesia
Intention tremor
Upper left quadrantanopia
Upper right quadrantanopia

Correct Answer

A. A UMN paralysis of the left side

Explanation

The tumor is situated in the lentiform nucleus and internal capsule. Therefore, corticospinal fibers will be affected, causing a UMN paralysis of the left side. Dyskinesia would not be seen because any effects normally seen in association with damage to the basal ganglia would be masked by the effects of the damage to the internal capsule. Since the cerebellum was not involved, there would be no intention tremor. Neither would there be any visual deficits from this glioma since optic nerve fibers are not involved. The following schematic diagram indicates the approximate extent of the tumor. Labeled are the caudate nucleus (C), the globus pallidus (GP), the internal capsule (IC), the putamen (P), and the tumor (T).

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10.

Audrey is a 45-year-old woman who was brought to her local hospital's emergency room by her husband because of several days of progressive weakness and numbness in her arms and legs. Her symptoms had begun with tingling in her toes, which she assumed to be her feet "falling asleep." However, this feeling did not disappear, and she began to feel numb, first in her toes on both feet, then ascending to her calves and knees. Two days later, Audrey began to feel numb in her fingertips, and had difficulty lifting her legs. When she finally was unable to climb the stairs of her house because of her leg weakness, difficulty gripping the banister, and shortness of breath, her husband urged her to go to the emergency room. The neurologist who examined Audrey in the emergency room noticed that she was short of breath while sitting in bed. He asked the respiratory therapist to measure her vital capacity (the greatest volume of air that can be exhaled from the lungs after a maximal inspiration), and the value for this was far lower than was expected for her age and weight. Her neurologic examination showed that her arms and legs were very weak, so that she had difficulty lifting them against gravity. She was unable to feel a pin or a vibrating tuning fork at all on her legs and below her elbows, but was able to feel the pin on her upper chest. The neurologist could not elicit any reflexes from her ankles or knees. He subsequently advised the emergency room staff that Audrey needed to have a spinal tap and be admitted to the intensive care unit immediately. Damage to which of the following nervous system structures caused the difficulty breathing?

Medullary respiratory center
Diencephalon
Pons
Phrenic nerve innervating the diaphragm
Trigeminal nerve

Correct Answer

A. Phrenic nerve innervating the diaphragm

Explanation

This is an example of a LMN problem. Answers a, b, and c are UMN structures. The trigeminal nerve is a cranial nerve that mediates sensation on the face and the muscles of mastication. Loss of diaphragmatic function causes respiratory distress.

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11.

Synthesis and storage of norepinephrine can be prevented by which of the following substances

Guanethidine sulfate
Reserpine
Phenoxybenzamine hydrochloride
Hexamethonium chloride
Metoprolol

Correct Answer

A. Reserpine

Explanation

Noradrenergic activity can be blocked by a number of mechanisms. Reserpine, for example, prevents the synthesis and storage of norepinephrine in sympathetic nerve terminals. Guanethidine sulfate affects noradrenergic transmission by blocking the release of norepinephrine at the sympathetic endings. Competitive alpha-receptor blockers include phenoxybenzamine hydrochloride and phentolamine, whereas metoprolol blocks beta1 receptors. Since ACh is the transmitter at preganglionic synapses of both the parasympathetic and sympathetic nervous systems, hexamethonium chloride is an effective ganglionic blocker at these synapses.

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12.

An individual who complains about disruption in limb muscle function is diagnosed with a disorder in which the transmitter released at the neuromuscular junction is not removed from the synaptic cleft. Which of the following is the primary mechanism involved in removal of the transmitter at the neuromuscular junction

Enzymatic degradation
Diffusion
Reuptake
Actions of antibodies
Distribution of sodium and potassium ions along muscle membrane

Correct Answer

A. Enzymatic degradation

Explanation

There are three basic mechanisms by which the transmitter is removed from the synaptic cleft: (1) enzymatic degradation, (2) reuptake, and (3) diffusion. In the case of the neuromuscular junction, ACh (and not glutamate) is the neurotransmitter and the primary mechanism involves enzymatic degradation. The enzyme involved is acetylcholinesterase, which helps break down ACh into acetate and choline. Choline is then taken up by the presynaptic terminal. Concerning the other choices, choline acetyltransferase is the enzyme involved in the synthesis of ACh, glutaminase, and glutamine synthetase are involved in the formation of glutamate from glutamine and glutamine from glutamate, respectively. Serine hydroxymethyltransferase is the enzyme that converts serine into glycine.

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13.

A patient experiences difficulty in walking down stairs and reports some double vision as well. Which of the following is the most likely locus of the lesion?

Medulla
Dorsal pons
Ventromedial pons
Midbrain
Spinal cord

Correct Answer

A. Midbrain

Explanation

To walk down stairs, one has to have the ability to move the eyes down when they are in the medial position. This involves the use of cranial nerve IV (trochlear nerve), which innervates the superior oblique muscle (whose action is to pull the eye downward when in the medial position). If there is damage to this nerve on one side, the eyes will not be able to focus on the same visual field, thus producing double vision. Cranial nerve IV is classified as a general somatic efferent fiber because it innervates skeletal muscle and it is derived from somites.

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14.

A patient experiences difficulty in walking down stairs and reports some double vision as well. The lesion most likely involved which of the following?

Cervical spinal cord ventral horn cells
Cranial nerve VII
Cranial nerve VI
Cranial nerve IV
Cranial nerve III

Correct Answer

A. Cranial nerve IV

Explanation

To walk down stairs, one has to have the ability to move the eyes down when they are in the medial position. This involves the use of cranial nerve IV (trochlear nerve), which innervates the superior oblique muscle (whose action is to pull the eye downward when in the medial position). If there is damage to this nerve on one side, the eyes will not be able to focus on the same visual field, thus producing double vision. Cranial nerve IV is classified as a general somatic efferent fiber because it innervates skeletal muscle and it is derived from somites.

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15.

An elderly female patient complains that she cannot taste the food that she eats. A careful neurological examination reveals no evidence of peripheral damage of the taste receptors. The evidence suggests, instead, that there was selective damage of certain regions of the brainstem. Damage to which of the following sites could result in the selective loss of taste?

Superior olivary nucleus
Inferior salivatory nucleus
Solitary nucleus
Spinal nucleus of the trigeminal nerve
Reticular tegmental nucleus of the pons

Correct Answer

A. Solitary nucleus

Explanation

The central pathways mediating taste include the following: primary afferent taste fibers associated with taste receptors of cranial nerves VII, IX, and X synapse in the solitary nucleus. Many fibers from the solitary nucleus project to the ventral posteromedial nucleus of the thalamus, which, in turn, project to the ventrolateral aspect of the postcentral gyrus.

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1

16.

Which of the following is the most ubiquitous excitatory neurotransmitter in the brain?

ACh
Glutamate
Norepinephrine
Dopamine
Substance P

Correct Answer

A. Glutamate

Explanation

The largest numbers of excitatory synapses in the CNS are mediated by glutamate as it is believed that approximately half of the synapses in the brain release glutamate. For example, functions mediated by fibers that originate from the cerebral cortex and descend to such regions as the neostriatum, thalamus, brainstem, and spinal cord are generally believed to be mediated by glutamate. Many other neuronal systems throughout the brain and spinal cord utilize glutamate as well. Dopaminergic and noradrenergic neurons, while mostly excitatory, can also be inhibitory at some synapses and are less numerous than glutamate. Cholinergic and substance P synapses are also excitatory, but are likewise less numerous than glutamate.

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17.

Audrey is a 45-year-old woman who was brought to her local hospital's emergency room by her husband because of several days of progressive weakness and numbness in her arms and legs. Her symptoms had begun with tingling in her toes, which she assumed to be her feet "falling asleep." However, this feeling did not disappear, and she began to feel numb, first in her toes on both feet, then ascending to her calves and knees. Two days later, Audrey began to feel numb in her fingertips, and had difficulty lifting her legs. When she finally was unable to climb the stairs of her house because of her leg weakness, difficulty gripping the banister, and shortness of breath, her husband urged her to go to the emergency room. The neurologist who examined Audrey in the emergency room noticed that she was short of breath while sitting in bed. He asked the respiratory therapist to measure her vital capacity (the greatest volume of air that can be exhaled from the lungs after a maximal inspiration), and the value for this was far lower than was expected for her age and weight. Her neurologic examination showed that her arms and legs were very weak, so that she had difficulty lifting them against gravity. She was unable to feel a pin or a vibrating tuning fork at all on her legs and below her elbows, but was able to feel the pin on her upper chest. The neurologist could not elicit any reflexes from her ankles or knees. He subsequently advised the emergency room staff that Audrey needed to have a spinal tap and be admitted to the intensive care unit immediately. Which receptor should be activated by the tuning fork?

C delta and A delta fibers
Merkel's tactile corpuscle
Pacinian corpuscle
Ruffini's corpuscle
Meissner's corpuscle

Correct Answer

A. Pacinian corpuscle

Explanation

Pacinian corpuscles best mediate vibration.

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18.

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has recently been applied experimentally with considerable success as a model for which of the following?

Huntington's disease
Hemiballism
Parkinson's disease
Tardive dyskinesia
Dystonia

Correct Answer

A. Parkinson's disease

Explanation

MPTP was discovered by accident when drug abusers who were using a synthetic heroin derivative developed signs of Parkinson's disease. It was discovered that their drug included the contaminant MPTP. As a consequence, MPTP has been applied systemically in a number of experimental animals, resulting in significant decreases in dopamine content of the brain due to the loss of dopaminergic neurons in the substantia nigra. These animals also developed symptoms similar to those seen in Parkinson's patients. For these reasons, this drug is currently being used for research purposes in order to develop a better understanding of this disease and to establish possible drug therapies for its treatment and eventual cure.

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19.

A number of investigations have provided strong evidence that the suprachiasmatic nucleus plays an important role in which of the following

Water intake
Food intake
Hypertension
Circadian rhythms
Short-term memory

Correct Answer

A. Circadian rhythms

Explanation

Recent studies have demonstrated that the suprachiasmatic nucleus controls the biologic clock of internal circadian rhythms. During the light phase of the light-dark cycle, metabolic activity (measured by 14C-2-deoxyglucose autoradiography) within the suprachiasmatic nucleus is significantly increased. In contrast, during the dark phase, there is very little metabolic activity.

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20.

A lesion of which region on the figure below will typically produce a disorder involving negligence of the opposite body half and visual space?

A
B
C
D
E

Correct Answer

A. B

Explanation

This figure is a lateral view of the cerebral cortex. Cells in the "arm" area of the primary motor cortex (H) project their axons to the cervical level of the spinal cord. This area receives major input from the ventrolateral nucleus of the thalamus. The leg region of the primary somatosensory cortex (A) lies immediately caudal to the central sulcus, is almost devoid of pyramidal cells, and is referred to as a granulous cortex. Damage to the cells situated in the region of the dorsal border of the superior temporal gyrus and the adjoining area of the inferior parietal lobule (Wernicke's area) (C) causes impairment in the appreciation of the meanings of written or spoken words.
The primary, secondary, and tertiary auditory receiving areas in the cortex are located mainly in the superior temporal gyrus (D). It is the final receiving area for inputs from the medial geniculate nucleus, which represents an important relay in the transmission of auditory signals to the cortex. An additional area of the cortex governing speech (F) is called the motor speech area, or Broca's area. It is situated in the inferior aspect of the frontal lobe immediately rostral and slightly ventral to the precentral gyrus. Lesions of this region produce impairment of the ability to express words in a meaningful way or to use words correctly. The orbital frontal cortex (E) lies in a position inferior and rostral to Broca's motor speech area. This region governs higher-order intellectual functions and some aspects of emotional behavior.
The caudal aspect of the middle frontal gyrus (G) contains cells that, when activated, produce conjugate deviation of the eyes. This action is believed to be accomplished, in part, by virtue of descending projections to the superior colliculus, pretectal region, and horizontal gaze center of the pons. Lesions of the posterior parietal lobe (B) of the nondominant hemisphere will produce a disorder of body image, referred to as sensory neglect. The patient will frequently fail to recognize or neglect to shave or wash those body parts. The patient may even fail to recognize the presence of a hemiparesis involving that part of the body as well. The precentral gyrus (H) constitutes the primary motor cortex. Lesions of this region produce a UMN paralysis involving a contralateral limb.

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21.

Gary is a 35-year-old man who was previously healthy until one day, when he noticed that his right leg was weak. As the day progressed, he found that he was dragging the leg behind him when he walked, and he finally asked a friend to drive him home from work because he was unable to lift his right foot up enough to place it on the gas peddle. He also noticed that his left leg felt a little bit numb. Finally, his wife convinced him to go to the emergency room of his local hospital. When Gary arrived at the emergency room, he was having a great deal of difficulty walking. The physician who examined him asked him when this began, and when Gary thought about it in more depth, he realized that perhaps this had started slowly several days before, and he had ignored the symptoms. Gary''s language function, cranial nerves, and motor and sensory examinations of his arms were within normal limits. When the physician examined Gary''s right leg, it was markedly weak, with very brisk reflexes in the knee and ankle. Vibration and position sense in the right leg were absent. Pain and temperature testing were normal in the right leg, but these sensations were absent on the left leg and abdomen to the level of his umbilicus. Reflexes in the left leg were normal, but when the physician scratched the lateral portion of the plantar surface on the bottom side of Gary''s right foot, the great toe moved up. The remainder of Gary''s examination was normal. What area of the nervous system is damaged?

Brainstem
Cervical spinal cord
Thoracic spinal cord
Frontal lobe
Peripheral nerves

Correct Answer

A. Thoracic spinal cord

Explanation

Gary has a spinal cord syndrome called Brown-Séquard''s syndrome, or hemisection of the spinal cord. The lesion is not at the cervical level because motor functions of the upper limbs were considered normal. The examiner can pinpoint the location of the lesion by using the "sensory level," or level at which the loss of pain and temperature begin, by remembering that the lesion affects fibers that have entered the spinal cord one or two levels below it, and then cross to the contralateral side. Therefore, a loss of sensory function at the T10 level indicates a lesion at the T8 or T9 level. A level at which motor deficits begin can be helpful as well, but in lesions of the thoracic spinal cord, muscles innervated by thoracic nerves are difficult to test. The examiner still expects weakness in the lower extremities, and this helps to make the diagnosis. Brown-Séquard''s syndrome may occur as a result of different types of tumors or infections of the spinal cord.

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22.

Gary is a 35-year-old man who was previously healthy until one day, when he noticed that his right leg was weak. As the day progressed, he found that he was dragging the leg behind him when he walked, and he finally asked a friend to drive him home from work because he was unable to lift his right foot up enough to place it on the gas peddle. He also noticed that his left leg felt a little bit numb. Finally, his wife convinced him to go to the emergency room of his local hospital. When Gary arrived at the emergency room, he was having a great deal of difficulty walking. The physician who examined him asked him when this began, and when Gary thought about it in more depth, he realized that perhaps this had started slowly several days before, and he had ignored the symptoms. Gary''s language function, cranial nerves, and motor and sensory examinations of his arms were within normal limits. When the physician examined Gary''s right leg, it was markedly weak, with very brisk reflexes in the knee and ankle. Vibration and position sense in the right leg were absent. Pain and temperature testing were normal in the right leg, but these sensations were absent on the left leg and abdomen to the level of his umbilicus. Reflexes in the left leg were normal, but when the physician scratched the lateral portion of the plantar surface on the bottom side of Gary''s right foot, the great toe moved up. The remainder of Gary''s examination was normal. Gary''s loss of left-sided pain and temperature sensation could be due to damage to which tract?

Right fasciculus cuneatus
Right fasciculus gracilis
Right spinothalamic tract
Left spinothalamic tract
Left corticospinal tract

Correct Answer

A. Right spinothalamic tract

Explanation

The spinothalamic tract carries fibers mediating pain and temperature. The primary pain fibers enter the spinal cord and pass one or two segments in Lissauer''s marginal zone before making a synapse with neurons that form the lateral spinothalamic tract. Fibers of the lateral spinothalamic tract then cross to the contralateral side one or two segments above or before where the primary afferent fibers have entered the cord. Accordingly, pain and temperature are lost below the lesion on the contralateral side. The cuneate and gracile fasciculi mediate proprioception and vibration, and the corticospinal tract mediates voluntary motor function.

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23.

A 56-year-old woman experiences a loss of taste affecting the front of her tongue and the ability to smile as a result of an infection. If the sensory loss involves damage of cell bodies, the specific group of neurons so affected would be which of the following?

Otic ganglion
Nodose (inferior) ganglion
Pterygopalatine ganglion
Geniculate ganglion
Trigeminal ganglion

Correct Answer

A. Geniculate ganglion

Explanation

Taste associated with the anterior two-thirds of the tongue is mediated by the facial (cranial nerve VII) nerve. The geniculate ganglion contains the cell bodies associated with the sensory (gustatory) component of the seventh nerve. The somatic motor component of the seventh nerve mediates the muscles of facial expression. Thus, the sensory and motor components of the seventh nerve affected in this individual can be characterized as special visceral afferent (because this afferent contains chemoreceptors) and special visceral efferent (because the motor component innervates skeletal muscle and is derived from a branchial arch), respectively.

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24.

Bladder functions are regulated by which of the following combinations of inputs

Vagal and sacral efferent fibers only
Vagal, sacral, and descending fibers from the cerebral cortex
Lumbar and sacral efferent fibers only
Lumbar, sacral, and descending fibers from the cerebral cortex
Lumbar, thoracic, and cervical fibers only

Correct Answer

A. Lumbar, sacral, and descending fibers from the cerebral cortex

Explanation

The smooth muscle of the bladder is innervated by postganglionic fibers of the sympathetic nervous system that arise from the inferior mesenteric ganglion. This ganglion, in turn, receives its inputs from T12–L2 of the intermediolateral cell column of the spinal cord. The smooth muscle of the bladder also receives inputs from postganglionic parasympathetic fibers that are innervated by preganglionic fibers arising from S2–S4. The external sphincter of the bladder (striated muscle) is innervated by ventral horn cells from the spinal cord. These ventral horn cells, in turn, receive inputs from supraspinal neurons that arise, in part, from the cerebral cortex. It is these neurons that form a part of the substrate for voluntary control over bladder functions.

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25.

. The conscious perception of movement is mediated by which of the following receptors

Meissner's corpuscles
Free nerve endings
Merkel's receptors
Joint capsules
Pacinian corpuscles

Correct Answer

A. Joint capsules

Explanation

Meissner's corpuscles, Merkel's receptors, and pacinian corpuscles respond to tactile, pressure, or possibly vibratory stimuli, while free nerve endings are associated with nociceptive stimuli. Joint capsules respond to movement of the limb, and the axons of these receptors contribute to the dorsal column–medial lemniscal system mediating the conscious perception of movement.

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26.

A man presents with a wide-based, ataxic gait during his attempts at walking. He also is unsteady and sways when standing and displays a tendency to fall backward or to either side in a drunken manner. A lesion is most likely located in which of the following?

Hemispheres of the posterior cerebellar lobe
Anterior limb of the internal capsule
Dentate nucleus
Anterior lobe of the cerebellum
Flocculonodular lobe of the cerebellum

Correct Answer

A. Flocculonodular lobe of the cerebellum

Explanation

Since the flocculonodular lobe receives and integrates inputs from the vestibular system, it is understandable why lesions that disrupt this integrating mechanism for vestibular inputs would result in difficulties in maintaining balance. Indeed, this is a classic feature of lesions of the flocculonodular lobe but is not associated with lesions in the hemispheres of the posterior lobe, anterior limb of the internal capsule, or the dentate nucleus, which are functionally linked to the frontal lobe. Lesions of the anterior lobe also do not affect mechanisms of balance.

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27.

Audrey is a 45-year-old woman who was brought to her local hospital's emergency room by her husband because of several days of progressive weakness and numbness in her arms and legs. Her symptoms had begun with tingling in her toes, which she assumed to be her feet "falling asleep." However, this feeling did not disappear, and she began to feel numb, first in her toes on both feet, then ascending to her calves and knees. Two days later, Audrey began to feel numb in her fingertips, and had difficulty lifting her legs. When she finally was unable to climb the stairs of her house because of her leg weakness, difficulty gripping the banister, and shortness of breath, her husband urged her to go to the emergency room. The neurologist who examined Audrey in the emergency room noticed that she was short of breath while sitting in bed. He asked the respiratory therapist to measure her vital capacity (the greatest volume of air that can be exhaled from the lungs after a maximal inspiration), and the value for this was far lower than was expected for her age and weight. Her neurologic examination showed that her arms and legs were very weak, so that she had difficulty lifting them against gravity. She was unable to feel a pin or a vibrating tuning fork at all on her legs and below her elbows, but was able to feel the pin on her upper chest. The neurologist could not elicit any reflexes from her ankles or knees. He subsequently advised the emergency room staff that Audrey needed to have a spinal tap and be admitted to the intensive care unit immediately. Where in the nervous system is the damage

Frontal lobe
Temporal lobe
Peripheral nerves and nerve roots
Spinal cord
Muscle

Correct Answer

A. Peripheral nerves and nerve roots

Explanation

This patient does not have a UMN lesion (spinal cord or above) because of the absent reflexes and ascending paralysis bilaterally involving all of the extremities. Lesions in the brain almost always give unilateral findings, and spinal cord lesions give a distinct level. The damage cannot be in the muscle, because the patient has sensory involvement, as well. This case is an example of Guillain-Barré syndrome, or an inflammatory disease of the peripheral nerve resulting from demyelination. Inflammatory cells are found within the nerves, as well as segmental demyelination and some degree of wallerian degeneration. This damage can cause an ascending paralysis and sensory loss, affecting the arms, face, and legs. The CSF often has a high protein level, making a spinal tap a useful test for the diagnosis of Guillain-Barré syndrome. Nerve conduction studies are also helpful in making the diagnosis. Most neurologists believe Guillain-Barré syndrome to be an immunologic reaction directed against the peripheral nerve, and some patients have a history of having had some type of infection prior to developing Guillain-Barré syndrome. However, a clear-cut cause is rarely found. Despite a known cause, most patients recover from Guillain-Barré syndrome, although the speed of recovery varies. Treatment is currently available (administration of gamma globulin), and, if instituted early in the course of the disease, decrease in the length of the illness is possible.

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28.

The proper sensory nucleus is derived from which of the following

Alar plate
Basal plate
Sulcus limitans
Neural crest
Roof plate

Correct Answer

A. Alar plate

Explanation

Structures associated with sensory functions, such as the proper sensory nucleus and the spinal nucleus of cranial nerve V, are derived from the alar plate

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29.

A brain MRI scan taken from a 6-month-old baby revealed that while the overall size of the cerebral cortex was normal, the size of the pyramidal tracts was considerably smaller than normal. Which of the following is the most likely explanation for this defect

Reduction in the numbers of cortical neurons giving rise to pyramidal tract fibers
Reduction in the numbers of synaptic contacts made by pyramidal tract neurons
Reduction in the extent of myelin found on pyramidal tract neurons
Reduction in the amount of neurotransmitter released by pyramidal tract neurons
Reduction in the numbers of glial cells attached to pyramidal tract neurons

Correct Answer

A. Reduction in the extent of myelin found on pyramidal tract neurons

Explanation

Extensive myelination occurs in postnatal development. The failure of the pyramidal tracts to form myelin would account for the reduction in their size. In this particular situation, the size of the cerebral cortex was approximately normal, suggesting that there was no significant decrease in cortical cells. Variation in the numbers of synaptic contacts, transmitter formation, and glial cells would not account for a reduction in the size of the pyramidal tract

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30.

A lesion of which region in the diagram below will likely result in receptive aphasia?

A
B
C
D
E

Correct Answer

A. C

Explanation

This figure is a lateral view of the cerebral cortex. Cells in the "arm" area of the primary motor cortex (H) project their axons to the cervical level of the spinal cord. This area receives major input from the ventrolateral nucleus of the thalamus. The leg region of the primary somatosensory cortex (A) lies immediately caudal to the central sulcus, is almost devoid of pyramidal cells, and is referred to as a granulous cortex. Damage to the cells situated in the region of the dorsal border of the superior temporal gyrus and the adjoining area of the inferior parietal lobule (Wernicke's area) (C) causes impairment in the appreciation of the meanings of written or spoken words.
The primary, secondary, and tertiary auditory receiving areas in the cortex are located mainly in the superior temporal gyrus (D). It is the final receiving area for inputs from the medial geniculate nucleus, which represents an important relay in the transmission of auditory signals to the cortex. An additional area of the cortex governing speech (F) is called the motor speech area, or Broca's area. It is situated in the inferior aspect of the frontal lobe immediately rostral and slightly ventral to the precentral gyrus. Lesions of this region produce impairment of the ability to express words in a meaningful way or to use words correctly. The orbital frontal cortex (E) lies in a position inferior and rostral to Broca's motor speech area. This region governs higher-order intellectual functions and some aspects of emotional behavior.
The caudal aspect of the middle frontal gyrus (G) contains cells that, when activated, produce conjugate deviation of the eyes. This action is believed to be accomplished, in part, by virtue of descending projections to the superior colliculus, pretectal region, and horizontal gaze center of the pons. Lesions of the posterior parietal lobe (B) of the nondominant hemisphere will produce a disorder of body image, referred to as sensory neglect. The patient will frequently fail to recognize or neglect to shave or wash those body parts. The patient may even fail to recognize the presence of a hemiparesis involving that part of the body as well. The precentral gyrus (H) constitutes the primary motor cortex. Lesions of this region produce a UMN paralysis involving a contralateral limb.

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31.

A lesion at which site in the figure below will produce a speech deficit, referred to as expressive aphasia?

C
D
E
F
G

Correct Answer

A. F

Explanation

This figure is a lateral view of the cerebral cortex. Cells in the "arm" area of the primary motor cortex (H) project their axons to the cervical level of the spinal cord. This area receives major input from the ventrolateral nucleus of the thalamus. The leg region of the primary somatosensory cortex (A) lies immediately caudal to the central sulcus, is almost devoid of pyramidal cells, and is referred to as a granulous cortex. Damage to the cells situated in the region of the dorsal border of the superior temporal gyrus and the adjoining area of the inferior parietal lobule (Wernicke's area) (C) causes impairment in the appreciation of the meanings of written or spoken words.
The primary, secondary, and tertiary auditory receiving areas in the cortex are located mainly in the superior temporal gyrus (D). It is the final receiving area for inputs from the medial geniculate nucleus, which represents an important relay in the transmission of auditory signals to the cortex. An additional area of the cortex governing speech (F) is called the motor speech area, or Broca's area. It is situated in the inferior aspect of the frontal lobe immediately rostral and slightly ventral to the precentral gyrus. Lesions of this region produce impairment of the ability to express words in a meaningful way or to use words correctly. The orbital frontal cortex (E) lies in a position inferior and rostral to Broca's motor speech area. This region governs higher-order intellectual functions and some aspects of emotional behavior.
The caudal aspect of the middle frontal gyrus (G) contains cells that, when activated, produce conjugate deviation of the eyes. This action is believed to be accomplished, in part, by virtue of descending projections to the superior colliculus, pretectal region, and horizontal gaze center of the pons. Lesions of the posterior parietal lobe (B) of the nondominant hemisphere will produce a disorder of body image, referred to as sensory neglect. The patient will frequently fail to recognize or neglect to shave or wash those body parts. The patient may even fail to recognize the presence of a hemiparesis involving that part of the body as well. The precentral gyrus (H) constitutes the primary motor cortex. Lesions of this region produce a UMN paralysis involving a contralateral limb.

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32.

The lesion at B would most likely result in which of the following deficits?

Paralysis of the contralateral limbs
Loss of conscious proprioception of the contralateral side of the body
Nystagmus
Lateral gaze paralysis
Facial paralysis

Correct Answer

A. Paralysis of the contralateral limbs

Explanation

Since the lesion is restricted to the medial aspect of the basilar part of the pons, the corticospinal tract would be affected, producing paralysis of the contralateral limbs. Although other structures would also be affected and could produce additional deficits, such deficits are not listed in this question. The other dysfunctions listed would not occur because they are associated with structures situated in the pontine tegmentum, which is not included in this lesion.

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33.

The supraoptic nucleus is most closely associated with which of the following?

Feeding behavior
Temperature regulation
Sexual behavior
Short-term memory functions
Water balance

Correct Answer

A. Water balance

Explanation

The supraoptic nucleus, like the paraventricular nucleus, contains magnocellular neurons that synthesize vasopressin and oxytocin and transport these hormones down their axons to the posterior pituitary. For this reason, the supraoptic nucleus plays a significant role in the regulation of water balance. There is no evidence to support the notion that the supraoptic nucleus has a role in feeding behavior, temperature regulation, sexual behavior, or short-term memory functions.

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34.

A lesion at which site in the figure below would typically produce an upper motor neuron (UMN) paralysis?

A
B
F
G
H

Correct Answer

A. H

Explanation

This figure is a lateral view of the cerebral cortex. Cells in the "arm" area of the primary motor cortex (H) project their axons to the cervical level of the spinal cord. This area receives major input from the ventrolateral nucleus of the thalamus. The leg region of the primary somatosensory cortex (A) lies immediately caudal to the central sulcus, is almost devoid of pyramidal cells, and is referred to as a granulous cortex. Damage to the cells situated in the region of the dorsal border of the superior temporal gyrus and the adjoining area of the inferior parietal lobule (Wernicke's area) (C) causes impairment in the appreciation of the meanings of written or spoken words.
The primary, secondary, and tertiary auditory receiving areas in the cortex are located mainly in the superior temporal gyrus (D). It is the final receiving area for inputs from the medial geniculate nucleus, which represents an important relay in the transmission of auditory signals to the cortex. An additional area of the cortex governing speech (F) is called the motor speech area, or Broca's area. It is situated in the inferior aspect of the frontal lobe immediately rostral and slightly ventral to the precentral gyrus. Lesions of this region produce impairment of the ability to express words in a meaningful way or to use words correctly. The orbital frontal cortex (E) lies in a position inferior and rostral to Broca's motor speech area. This region governs higher-order intellectual functions and some aspects of emotional behavior.
The caudal aspect of the middle frontal gyrus (G) contains cells that, when activated, produce conjugate deviation of the eyes. This action is believed to be accomplished, in part, by virtue of descending projections to the superior colliculus, pretectal region, and horizontal gaze center of the pons. Lesions of the posterior parietal lobe (B) of the nondominant hemisphere will produce a disorder of body image, referred to as sensory neglect. The patient will frequently fail to recognize or neglect to shave or wash those body parts. The patient may even fail to recognize the presence of a hemiparesis involving that part of the body as well. The precentral gyrus (H) constitutes the primary motor cortex. Lesions of this region produce a UMN paralysis involving a contralateral limb.

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35.

Audrey is a 45-year-old woman who was brought to her local hospital's emergency room by her husband because of several days of progressive weakness and numbness in her arms and legs. Her symptoms had begun with tingling in her toes, which she assumed to be her feet "falling asleep." However, this feeling did not disappear, and she began to feel numb, first in her toes on both feet, then ascending to her calves and knees. Two days later, Audrey began to feel numb in her fingertips, and had difficulty lifting her legs. When she finally was unable to climb the stairs of her house because of her leg weakness, difficulty gripping the banister, and shortness of breath, her husband urged her to go to the emergency room. The neurologist who examined Audrey in the emergency room noticed that she was short of breath while sitting in bed. He asked the respiratory therapist to measure her vital capacity (the greatest volume of air that can be exhaled from the lungs after a maximal inspiration), and the value for this was far lower than was expected for her age and weight. Her neurologic examination showed that her arms and legs were very weak, so that she had difficulty lifting them against gravity. She was unable to feel a pin or a vibrating tuning fork at all on her legs and below her elbows, but was able to feel the pin on her upper chest. The neurologist could not elicit any reflexes from her ankles or knees. He subsequently advised the emergency room staff that Audrey needed to have a spinal tap and be admitted to the intensive care unit immediately. Audrey can't feel a pinprick in certain locations. Which receptor carries this information?

Merkel's tactile disk
Ruffini's corpuscle
Pacinian corpuscle
C delta and A delta fibers
Meissner's corpuscle

Correct Answer

A. C delta and A delta fibers

Explanation

Pain is mediated by C delta and A delta fibers in the skin.

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36.

An elderly female patient complains that she cannot taste the food that she eats. A careful neurological examination reveals no evidence of peripheral damage of the taste receptors. The evidence suggests, instead, that there was selective damage of certain regions of the brainstem. Which of the following is a principal target of the brainstem structure

Anterior thalamic nucleus
Reticular thalamic nucleus
Ventral posteromedial thalamic nucleus
Ventrolateral thalamic nucleus
Dorsomedial thalamic nucleus

Correct Answer

A. Ventral posteromedial thalamic nucleus

Explanation

The central pathways mediating taste include the following: primary afferent taste fibers associated with taste receptors of cranial nerves VII, IX, and X synapse in the solitary nucleus. Many fibers from the solitary nucleus project to the ventral posteromedial nucleus of the thalamus, which, in turn, project to the ventrolateral aspect of the postcentral gyrus.

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37.

An impairment in the ability to perform certain types of learned, complex movements (referred to as apraxia) usually results from a lesion of which of the following?

Precentral gyrus
Postcentral gyrus
Premotor cortex
Prefrontal cortex
Cingulate gyrus

Correct Answer

A. Premotor cortex

Explanation

The premotor areas play an important role in the programming or sequencing of responses that compose complex learned movements. They receive significant inputs for this process from the posterior parietal lobule and, in turn, signal appropriate neurons in the brainstem and spinal cord (both flexors and extensors). Lesions of the postcentral gyrus produce a somatosensory loss. Lesions of the precentral gyrus produce paralysis. Neither lesions of the prefrontal cortex nor those of the cingulate gyrus have been reported to produce apraxia.

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38.

Gary is a 35-year-old man who was previously healthy until one day, when he noticed that his right leg was weak. As the day progressed, he found that he was dragging the leg behind him when he walked, and he finally asked a friend to drive him home from work because he was unable to lift his right foot up enough to place it on the gas peddle. He also noticed that his left leg felt a little bit numb. Finally, his wife convinced him to go to the emergency room of his local hospital. When Gary arrived at the emergency room, he was having a great deal of difficulty walking. The physician who examined him asked him when this began, and when Gary thought about it in more depth, he realized that perhaps this had started slowly several days before, and he had ignored the symptoms. Gary''s language function, cranial nerves, and motor and sensory examinations of his arms were within normal limits. When the physician examined Gary''s right leg, it was markedly weak, with very brisk reflexes in the knee and ankle. Vibration and position sense in the right leg were absent. Pain and temperature testing were normal in the right leg, but these sensations were absent on the left leg and abdomen to the level of his umbilicus. Reflexes in the left leg were normal, but when the physician scratched the lateral portion of the plantar surface on the bottom side of Gary''s right foot, the great toe moved up. The remainder of Gary''s examination was normal. Damage to which tract could give Gary the loss of vibration and position sense on the right side?

Right fasciculus cuneatus
Right fasciculus gracilis
Left fasciculus cuneatus
Left fasciculus gracilis
Right Lissauer''s tract

Correct Answer

A. Right fasciculus gracilis

Explanation

Because one-half of the spinal cord is damaged, the dorsal columns are damaged, and the patient will have loss of proprioception and vibration ipsilateral to and below the level of the lesion. The loss must be ipsilateral because fibers mediating this type of sensation cross above the level of the lesion. The fasciculus gracilis carries fibers originating from the sacral, lumbar, and lower thoracic levels, and the fasciculus cuneatuse carries those from the upper thoracic and cervical levels. Lissauer''s tract carries pain and temperature fibers via the dorsal root entry zone. Brown-Séquard''s syndrome may occur as a result of different types of tumors or infections of the spinal cord.

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39.

As a result of calcification of the internal carotid artery, which impinges upon the lateral half of the right optic nerve prior to its entrance to the brain of a 68-year-old woman, resulting in certain visual deficits. Which of the following is the most likely visual deficits

Total blindness of the right eye
Right nasal hemianopsia
Right homonymous hemianopsia
Right bitemporal hemianopsia
Right upper homonymous quadrantanopia

Correct Answer

A. Right nasal hemianopsia

Explanation

Calcification of the internal carotid artery could serve to disrupt nerve fibers proximal to it. One such group of fibers includes parts of the optic nerve. In this case, the component of the right optic nerve affected includes the lateral aspect, or those fibers that mediate vision associated with the nasal visual field of the right eye. If the damage were more extensive and if it involved the entire nerve, then total blindness of the right eye would have occurred.

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40.

A 43-year-old male is recovering from an infectious disease and experiences a marked instability in his blood pressure with episodes of spiking of blood pressure. After a series of extensive examinations, it was concluded that this disorder was due to the effects of the infectious agent upon a component of the peripheral nervous system. Logical sites where an infectious agent could produce such an effect include which of the following

Superior ganglia of cranial nerves IX and X
Geniculate and trigeminal ganglia
Otic and superior salivatory ganglia
Carotid sinus and aortic arch
Carotid and aortic bodies

Correct Answer

A. Carotid sinus and aortic arch

Explanation

Specialized peripheral receptors, which specifically respond to changes in blood pressure, include the carotid sinus (associated with cranial nerve IX) and the aortic arch (associated with cranial nerve X). If these receptors (or the cell bodies associated with these receptors) are damaged, then one of the fundamental regulatory mechanisms for the control of blood pressure would be disrupted. The results of such a disruption would likely lead to increases and instability in blood pressure with evidence of spiking of blood pressure. Because these sensory receptors in these structures respond to increases in blood pressure, they are, in effect, stretch receptors and are consequently referred to as baroreceptors. The principal projection of the axons associated with these baroreceptors is the solitary nucleus of the medulla, which in turn, projects to autonomic nuclei such as the dorsal motor nucleus of the vagus nerve, ventrolateral medulla, and higher regions associated with autonomic functions, which include the PAG, hypothalamus, and limbic system.

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41.

A 40-year-old male who had been suffering from a disorder of unknown origin complains to his physician that he has difficulty in producing a smile from the left side of his face, and that he can't salivate or produce tears from the left eye. Further analysis showed some loss of taste and that the affected muscles were flaccid and the eyelids were open. Which of the following is the most likely locus of this lesion?

Nucleus of the facial nerve
Inferior and superior ganglia of cranial nerve IX
Geniculate ganglion
Cerebral cortex
Reticular formation

Correct Answer

A. Geniculate ganglion

Explanation

The nerve affected by this disorder is cranial nerve VII (facial nerve). The cell bodies of origin, which innervate the muscles of facial expression (special visceral efferents), arise from the facial nucleus, which are located in the ventrolateral aspect of the lower pons. The preganglionic parasympathetic neurons, which synapse with postganglionic neurons in the submandibular and pterygopalatine ganglia, arise from the superior salivatory nucleus of the lower pons. The most likely locus of the defect is the geniculate ganglion. The region of the geniculate ganglion and regions adjacent to it contain sensory, skeletal, and visceral motor components of this nerve. Therefore, disruption of this nerve in the region of the geniculate ganglion will produce the constellation of deficits described in this case. The other choices are not appropriate. Cranial nerve IX is not involved. Neither are the regions of the reticular formation and facial nucleus, because lesions at either of these locations could not account for the totality of deficits described in this case. The lesion could not have involved the cerebral cortex because the motor effects were described as a flaccid facial paralysis. A cortical lesion does not produce flaccidity of these muscles.

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42.

A 56-year-old woman experiences a loss of taste affecting the front of her tongue and the ability to smile as a result of an infection. The components of the nerve that is affected include which of the following

General somatic afferent and general somatic efferent
Special visceral afferent and special visceral efferent
General visceral afferent and general somatic efferent
General somatic afferent and general visceral efferent
Special visceral afferent and general visceral efferent

Correct Answer

A. Special visceral afferent and special visceral efferent

Explanation

Taste associated with the anterior two-thirds of the tongue is mediated by the facial (cranial nerve VII) nerve. The geniculate ganglion contains the cell bodies associated with the sensory (gustatory) component of the seventh nerve. The somatic motor component of the seventh nerve mediates the muscles of facial expression. Thus, the sensory and motor components of the seventh nerve affected in this individual can be characterized as special visceral afferent (because this afferent contains chemoreceptors) and special visceral efferent (because the motor component innervates skeletal muscle and is derived from a branchial arch), respectively.

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43.

A 40-year-old male who had been suffering from a disorder of unknown origin complains to his physician that he has difficulty in producing a smile from the left side of his face, and that he can't salivate or produce tears from the left eye. Further analysis showed some loss of taste and that the affected muscles were flaccid and the eyelids were open. The cell bodies of origin within the central nervous system (CNS) whose peripheral innervation of skeletal muscles were affected by this disorder lie in which of the following?

Upper medulla
Lower pons
Upper pons
Lower midbrain
Upper midbrain

Correct Answer

A. Lower pons

Explanation

The nerve affected by this disorder is cranial nerve VII (facial nerve). The cell bodies of origin, which innervate the muscles of facial expression (special visceral efferents), arise from the facial nucleus, which are located in the ventrolateral aspect of the lower pons. The preganglionic parasympathetic neurons, which synapse with postganglionic neurons in the submandibular and pterygopalatine ganglia, arise from the superior salivatory nucleus of the lower pons. The most likely locus of the defect is the geniculate ganglion. The region of the geniculate ganglion and regions adjacent to it contain sensory, skeletal, and visceral motor components of this nerve. Therefore, disruption of this nerve in the region of the geniculate ganglion will produce the constellation of deficits described in this case. The other choices are not appropriate. Cranial nerve IX is not involved. Neither are the regions of the reticular formation and facial nucleus, because lesions at either of these locations could not account for the totality of deficits described in this case. The lesion could not have involved the cerebral cortex because the motor effects were described as a flaccid facial paralysis. A cortical lesion does not produce flaccidity of these muscles.

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44.

A 40-year-old male who had been suffering from a disorder of unknown origin complains to his physician that he has difficulty in producing a smile from the left side of his face, and that he can't salivate or produce tears from the left eye. Further analysis showed some loss of taste and that the affected muscles were flaccid and the eyelids were open. The preganglionic parasympathetic fibers of this nerve arise from which of the following

Dorsal motor nucleus of the vagus
Nucleus ambiguus
Inferior salivatory nucleus
Superior salivatory nucleus
Edinger-Westphal nucleus of cranial nerve III

Correct Answer

A. Superior salivatory nucleus

Explanation

The nerve affected by this disorder is cranial nerve VII (facial nerve). The cell bodies of origin, which innervate the muscles of facial expression (special visceral efferents), arise from the facial nucleus, which are located in the ventrolateral aspect of the lower pons. The preganglionic parasympathetic neurons, which synapse with postganglionic neurons in the submandibular and pterygopalatine ganglia, arise from the superior salivatory nucleus of the lower pons. The most likely locus of the defect is the geniculate ganglion. The region of the geniculate ganglion and regions adjacent to it contain sensory, skeletal, and visceral motor components of this nerve. Therefore, disruption of this nerve in the region of the geniculate ganglion will produce the constellation of deficits described in this case. The other choices are not appropriate. Cranial nerve IX is not involved. Neither are the regions of the reticular formation and facial nucleus, because lesions at either of these locations could not account for the totality of deficits described in this case. The lesion could not have involved the cerebral cortex because the motor effects were described as a flaccid facial paralysis. A cortical lesion does not produce flaccidity of these muscles.

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45.

A patient with the lesion at A will generally show which of the following deficits?

Partial blindness
Loss of ability to gaze medially
Loss of ability to show tracking movements
Loss of accommodation reflex
Nystagmus

Correct Answer

A. Loss of ability to show tracking movements

Explanation

The lesion involves the superior colliculus. This structure receives inputs from the cerebral cortex and optic tract and its neurons respond to moving objects in the visual field. It is considered essential for the regulation of tracking movements. Lesions of the superior colliculus have not been shown to produce any of the other deficits listed in this question. Nystagmus is not likely to occur because the lesion does not involve the medial longitudinal fasciculus or the pontine gaze center.

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46.

. Which one of the following thalamic nuclei makes local connections with other thalamic nuclei and, additionally, projects to the basal ganglia

Centromedian thalamic nucleus
Medial geniculate thalamic nucleus
Lateral geniculate thalamic nucleus
Dorsomedial thalamic nucleus
Anterior thalamic nucleus

Correct Answer

A. Centromedian thalamic nucleus

Explanation

The centromedian nucleus is a classical nonspecific thalamic nucleus. It can modulate cortical activity by making local connections with specific thalamic nuclei, and therefore modify the specific thalamic inputs to different regions of the cerebral cortex. In addition, the centromedian nucleus also projects to the putamen. This projection is sometimes referred to as the thalamostriatal projection. Since the centromedian nucleus receives considerable inputs from the cerebral cortex, this connection to the putamen provides a basis by which the cerebral cortex can influence the basal ganglia in addition to its direct projections to the neostriatum.

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47.

Which of the following is the primary transmitter released from terminals of both neostriatal and paleostriatal neurons?

Glycine
Enkephalin
Dopamine
GABA
Glutamate

Correct Answer

A. GABA

Explanation

The major transmitter released at terminals of neostriatal and paleostriatal fibers is GABA. Thus, the output of the basal ganglia is mainly inhibitory. This suggests that thalamic influences upon the cortex are generated through the process of disinhibition, whereby neurons of the basal ganglia are inhibited. The presence of glycine in striatal neurons has yet to be demonstrated. Enkephalins are released from terminals of neostriatal-pallidal fibers but not from other efferent neurons of the striatum. Dopamine is released from the brainstem and some adjoining hypothalamic neurons but certainly not from striatal neurons. The neostriatum receives cortical inputs that utilize glutamate, but the release of GABA from terminals of striatal efferent fibers has not been demonstrated.

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48.

Emma is a 64-year-old woman who has had heart disease for many years. While carrying chemicals down the stairs of the dry-cleaning shop where she worked, she suddenly lost control of her right leg and arm. She fell down the stairs and was able to stand up with some assistance from a coworker. When attempting to walk on her own, she had a very unsteady gait, with a tendency to fall to the right side. Her supervisor asked her if she was all right, and noticed that her speech was very slurred when she tried to answer. He called an ambulance to take her to the nearest hospital. The physician who was called to see Emma in the emergency room noted that her speech was slurred as if she were intoxicated, but the grammar and meaning were intact. Her face appeared symmetric, but when asked to protrude her tongue, it deviated toward the left. She was unable to tell if her right toe was moved up or down by the physician when she closed her eyes, and she couldn't feel the buzz of a tuning fork on her right arm and leg. In addition, her right arm and leg were markedly weak. The physician could find no other abnormalities on the remainder of Emma's general medical examination. Where in the nervous system has the damage occurred?

Right lateral medulla
Occipital lobe
Left lateral medulla
Right cervical spinal cord
Left medial medulla

Correct Answer

A. Left medial medulla

Explanation

Emma has had a stroke resulting from occlusion of medial branches of the left vertebral artery, presumably secondary to atherosclerosis (i.e., cholesterol deposits within the artery, which eventually occlude it). The resulting syndrome is called the medial medullary syndrome, because the affected structures are located in the medial portion of the medulla. These structures include: the pyramids, the medial lemniscus, the medial longitudinal fasciculus, and the nucleus of the hypoglossal nerve and its outflow tract. Emma's symptoms result from damage to the aforementioned structures, and may have been caused by the same process (atherosclerosis) that resulted in her heart disease. The weakness of her right side was caused by damage to the medullary pyramid on the left side. Her face was spared because fibers supplying the face exited above the level of infarct. However, a lesion in the corticospinal tract of the cervical spinal cord above C5 could cause arm and leg weakness, and spare the face, because facial fibers exit in the rostral medulla. A lesion in the inferior portion of the precentral gyrus of the left frontal lobe would cause right-sided weakness, but would include the face, because this area is represented more inferiorly than are the extremities. Her unsteady gait was a result of the weakness of her right side, but may also have been the result of the loss of position and vibration sense on that side from damage to the medial lemniscus (as demonstrated by the inability to identify the position of her toe with her eyes closed, and the inability to feel the vibrations of a tuning fork). Without position sense, walking becomes unsteady because it is necessary to feel the position of one's feet on the floor during normal gait. Damage to both the medial lemniscus and pyramids at this level causes problems on the contralateral side because this lesion is located rostral to the level where both of these fiber bundles cross to the opposite side of the brain. Damage to the descending component of the medial longitudinal fasciculus could only affect head and neck reflexes, but not gait. Gait is also unaffected by pain inputs. Deviation of the tongue occurs because fibers from the hypoglossal nucleus innervate the genioglossus muscle on the ipsilateral side of the tongue. This muscle normally protrudes the tongue toward the contralateral side. Therefore, if one side is weak, the tongue will deviate toward the side ipsilateral to the lesion when protruded. A lesion in the precentral gyrus causes protrusion of the tongue toward the side that is contralateral to the lesion, because it is rostral to the crossing of fibers into the hypoglossal nucleus. Emma's speech was dysarthric (slurred) because her tongue was weak on the left side. The physician saw this during the exam when her tongue deviated to the left when protruded. Since the weakness of the tongue is purely a motor problem, rather than an effect that is manifested by a lesion to higher centers in the cortex (which mediate the structure and function of speech), the grammar, content, and meaning of Emma's speech remained intact, as would be expected with an aphasia or agnosia.

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49.

. A 55-year-old woman complains of headaches and is subsequently diagnosed as having a tumor localized to the left parietal lobe. In addition to a variety of sensory deficits, further examination also reveals a reduction in her visual fields. Which of the following is the most likely visual deficit

Left homonymous hemianopsia
Right homonymous hemianopsia
Left upper quadrantanopia
Right upper quadrantanopia
Right lower quadrantanopia

Correct Answer

A. Right lower quadrantanopia

Explanation

Fibers from the left lateral geniculate destined for the upper bank of the calcarine fissure will mediate visual impulses associated with lower quadrants of the right visual fields for both eyes. This deficit is referred to as a right lower quadrantanopia.

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USMLE Step 1 Qs (8)

Quiz Preview

A 56-year-old woman experiences a loss of taste affecting the front of her tongue and the ability to smile as a result of an infection. Which of the following cranial nerve is most immediately affected?

Epileptiform activity is believed to include the activation of which of the following

A person is told that he has astigmatism. To correct this defect, the optometrist prescribes which of the following lenses

Which of the following enzymes is directly responsible for the degradation of norepinephrine

The CT scan below reveals that the patient has a glioma (T) on the right side of the brain. It is likely that the patient has sustained which of the following?

Synthesis and storage of norepinephrine can be prevented by which of the following substances

A patient experiences difficulty in walking down stairs and reports some double vision as well. Which of the following is the most likely locus of the lesion?

A patient experiences difficulty in walking down stairs and reports some double vision as well. The lesion most likely involved which of the following?

Which of the following is the most ubiquitous excitatory neurotransmitter in the brain?

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has recently been applied experimentally with considerable success as a model for which of the following?

A number of investigations have provided strong evidence that the suprachiasmatic nucleus plays an important role in which of the following

A lesion of which region on the figure below will typically produce a disorder involving negligence of the opposite body half and visual space?

A 56-year-old woman experiences a loss of taste affecting the front of her tongue and the ability to smile as a result of an infection. If the sensory loss involves damage of cell bodies, the specific group of neurons so affected would be which of the following?

Bladder functions are regulated by which of the following combinations of inputs

. The conscious perception of movement is mediated by which of the following receptors

A man presents with a wide-based, ataxic gait during his attempts at walking. He also is unsteady and sways when standing and displays a tendency to fall backward or to either side in a drunken manner. A lesion is most likely located in which of the following?

The proper sensory nucleus is derived from which of the following

A brain MRI scan taken from a 6-month-old baby revealed that while the overall size of the cerebral cortex was normal, the size of the pyramidal tracts was considerably smaller than normal. Which of the following is the most likely explanation for this defect

A lesion of which region in the diagram below will likely result in receptive aphasia?

A lesion at which site in the figure below will produce a speech deficit, referred to as expressive aphasia?

The lesion at B would most likely result in which of the following deficits?

The supraoptic nucleus is most closely associated with which of the following?

A lesion at which site in the figure below would typically produce an upper motor neuron (UMN) paralysis?

An impairment in the ability to perform certain types of learned, complex movements (referred to as apraxia) usually results from a lesion of which of the following?

As a result of calcification of the internal carotid artery, which impinges upon the lateral half of the right optic nerve prior to its entrance to the brain of a 68-year-old woman, resulting in certain visual deficits. Which of the following is the most likely visual deficits

A 56-year-old woman experiences a loss of taste affecting the front of her tongue and the ability to smile as a result of an infection. The components of the nerve that is affected include which of the following

A patient with the lesion at A will generally show which of the following deficits?

. Which one of the following thalamic nuclei makes local connections with other thalamic nuclei and, additionally, projects to the basal ganglia

Which of the following is the primary transmitter released from terminals of both neostriatal and paleostriatal neurons?

. A 55-year-old woman complains of headaches and is subsequently diagnosed as having a tumor localized to the left parietal lobe. In addition to a variety of sensory deficits, further examination also reveals a reduction in her visual fields. Which of the following is the most likely visual deficit