USMLE Step 1 Qs (11)
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questions from various sources for practicing
Questions and Answers
- 1.
. A patient is capable of displaying pupillary constriction during an accommodation reaction but not in response to a direct-light stimulus. The lesion is most likely present in which of the following
- A.
Optic nerve
- B.
Ventral cell column of cranial nerve III
- C.
Pretectal area
- D.
Visual cortex
- E.
Edinger-Westphal nucleus of cranial nerve III
Correct Answer
C. Pretectal areaExplanation
This disorder is referred to as the Argyll Robertson pupil and occurs with CNS syphilis (tertiary). Although the precise site of the lesion has never been fully established, it is believed to be in the pretectal area. The reasoning is as follows: In the pupillary light reflex, many optic fibers terminate in the pretectal area and superior colliculus region and are then relayed to the autonomic nuclei of cranial nerve III. Impulses from this component of cranial nerve III then synapse with postganglionic parasympathetics that innervate the pupillary constrictor muscles, thus producing pupillary constriction. In the case of the accommodation reflex, retinal impulses first reach the cortex and are then relayed through corticofugal fibers to the brainstem. Some of these fibers are then relayed directly or indirectly to both motor and autonomic components of cranial nerve III, thus activating the muscles required for the accommodation reaction to occur, which includes pupillary constriction.Rate this question:
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- 2.
Which of the following deficits is likely to occur as a result of the lesion at B?
- A.
Contralateral loss of conscious proprioception
- B.
Transient tremor of the ipsilateral limb
- C.
Ipsilateral fourth-nerve palsy
- D.
Hearing loss
- E.
Contralateral loss of taste sensation
Correct Answer
A. Contralateral loss of conscious proprioceptionExplanation
The lesion will disrupt fibers of the medial lemniscus (lateral aspect of the lesion) and thus produce contralateral loss of conscious proprioception. It will also disrupt fibers passing from the cerebellum to the red nucleus and ventrolateral nucleus of the thalamus, which could account for a tremor of the contralateral limb. Note that there would be no ipsilateral motor loss because functions associated with the red nucleus are expressed on the contralateral side. Oculomotor palsy would also be present because the lesion disrupts root fibers of cranial nerve III. However, the lesion is too rostral to affect cranial nerve IV. There is no hearing loss because the auditory fibers are situated too far laterally. Since the taste pathway is essentially ipsilateral, if any fibers are damaged by the lesion, deficits in taste sensation would be ipsilateral.Rate this question:
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- 3.
The deficits associated with the lesion at C are the result of damage to which of the following?
- A.
Substantia nigra and crus cerebri
- B.
Red nucleus and crus cerebri
- C.
Crus cerebri and cranial nerve III
- D.
Red nucleus and substantia nigra
- E.
Substantia nigra and cranial nerve III
Correct Answer
C. Crus cerebri and cranial nerve IIIExplanation
The primary structures damaged by this lesion include the crus cerebri, which results in a UMN paralysis of the contralateral limbs, as well as a paresis of the lower facial and tongue muscles. The other outstanding syndrome present from this lesion is a paralysis that results from damage to cranial nerve III. Other structures may be marginally affected.Rate this question:
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- 4.
Which of the following is the principal ascending auditory pathway of the brainstem?
- A.
Medial lemniscus
- B.
Lateral lemniscus
- C.
Trapezoid body
- D.
Trigeminal lemniscus
- E.
Brachium of the superior colliculus
Correct Answer
B. Lateral lemniscusExplanation
The principal ascending pathway of the auditory system listed in this question is the lateral lemniscus. It transmits information from the cochlear nuclei to the inferior colliculus. The trapezoid body is a commissure that contains some of the fibers of the lateral lemniscus that cross from the cochlear nuclei of one side of the brainstem en route to the inferior colliculus of the other side. The trapezoid body is present at the level of the caudal pons. The brachium of the superior colliculus, trigeminal lemniscus, and medial lemniscus do not transmit auditory sensory information.Rate this question:
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- 5.
The output of the retina is mediated by which of the following
- A.
Bipolar cells
- B.
Horizontal cells
- C.
Rods
- D.
Cones
- E.
Ganglion cells
Correct Answer
E. Ganglion cellsExplanation
The output of the retina is mediated by the ganglion cells. Ganglion cells receive inputs from photoreceptor and bipolar cells. In turn, ganglion cells give rise to optic nerve fibers, which project through the optic chiasm and optic tracts to the lateral geniculate nucleus of the thalamus. Other cells mentioned in this question only produce local connections within the retina.Rate this question:
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- 6.
Which of the following is a direct interneuron linking the receptor and ganglion cells
- A.
Bipolar cell
- B.
Horizontal cell
- C.
Golgi cell
- D.
Amacrine cell
- E.
Optic nerve cell
Correct Answer
A. Bipolar cellExplanation
The bipolar cell receives inputs from the receptor cells (i.e., rods and cones). The response of the bipolar cell to the receptor cell input is then mediated to the ganglion cell. Horizontal and amacrine cells connect neighboring receptor or bipolar cells; Golgi cells are not present in the retina; and optic nerve cells project out of the retina as indicated earlier.Rate this question:
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- 7.
An individual is diagnosed with retinitis pigmentosa, which produces a defective opsin. This defect will most likely result in which of the following
- A.
Degeneration of area 17 of the cerebral cortex
- B.
Degeneration of cone cells
- C.
Loss of central vision
- D.
Total loss of vision
- E.
Reduced response to light
Correct Answer
E. Reduced response to lightExplanation
In one form of retinitis pigmentosa, there is a genetic defect with respect to rhodopsin. The result of this defect is the production of defective opsin. As a consequence, rod cells are affected, leading to a reduced response to light. However, central vision is spared as are cone cells. Central nervous system (CNS) neurons such as those located in area 17 are not directly affected and vision is not totally lost.Rate this question:
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- 8.
A patient complains of having constant headaches involving the frontal region. Further examination reveals increased intraocular pressure. The pupil is dilated but, at the time of examination, there is little evidence of visual deficits. Which of the following is the most likely diagnosis?
- A.
Cataracts
- B.
A tumor of the visual cortex or lateral geniculate nucleus
- C.
A tumor at the base of the brain impinging upon the optic chiasm
- D.
Glaucoma
- E.
Color blindness
Correct Answer
D. GlaucomaExplanation
Glaucoma is a condition of elevated intraocular pressure caused (perhaps by infection) when debris accumulates in the spaces that lead to Schlemm's canal. If not treated, it can rapidly lead to blindness because the pressure can block conduction along the optic nerve. In addition, glaucoma can also be associated with frontal headaches; the diagnosis can be identified by determining the intraocular pressure.Rate this question:
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- 9.
routine eye examination reveals the presence of inflammation limited to the left optic disk, probably due to neuritis of this region. Which of the following is the most likely visual deficit resulting from this disorder
- A.
Total blindness of the left eye
- B.
Left homonymous hemianopsia
- C.
Left heteronymous hemianopsia
- D.
Left enlargement of the blind spot
- E.
Left upper quadrantanopia
Correct Answer
D. Left enlargement of the blind spotExplanation
A neuritis involving the optic disk would affect the size of the visual field loss around the optic disk, which corresponds to the blind spot. In general, this kind of neuritis would expand somewhat the size of the blind spot but would cause no further visual loss.Rate this question:
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- 10.
A 29-year-old male has a tumor pressing on the base of the brain where it is impinging upon the optic chiasm. He discovers that his field of vision is now seriously affected. Which of the following defects is present in this individual?
- A.
Total blindness of both eyes
- B.
Bitemporal hemianopsia
- C.
Right homonymous hemianopsia
- D.
Binasal hemianopsia
- E.
Right lower homonymous quadrantanopia
Correct Answer
B. Bitemporal hemianopsiaExplanation
A tumor pressing on the optic chiasm will disrupt the optic nerve (and tract) fibers that cross to the opposite side. These fibers mediate vision associated with fibers arising from the nasal retina of each eye. Since the nasal retina of each eye is associated with the temporal visual field for each eye, the visual loss is referred to as a bitemporal hemianopsia.Rate this question:
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- 11.
. A routine magnetic resonance imaging (MRI) reveals the presence of a tumor situated in the left optic tract proximal to the lateral geniculate nucleus. The patient complained of having a reduction in his field of vision. Which of the following is the most likely visual deficit
- A.
Total blindness of the left eye
- B.
Bitemporal hemianopsia
- C.
Right homonymous hemianopsia
- D.
Left homonymous hemianopsia
- E.
Left homonymous quadrantanopia
Correct Answer
C. Right homonymous hemianopsiaExplanation
Disruption of optic tract fibers destined for the lateral geniculate nucleus will cause a homonymous hemianopsia because it affects fibers arising from the temporal retina of the ipsilateral side and from the nasal retina of the contralateral side. Since the damage occurred in the left optic tract, the loss of vision is reflected on the right visual field [i.e., the left temporal retina is associated with the nasal (or right) visual field of the left eye, and the right nasal retina is associated with the temporal (or right) visual field of the right eye]. Therefore, such a lesion would result in a right homonymous hemianopsia.Rate this question:
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- 12.
A 70-year-old male is admitted to the emergency room and a subsequent MRI reveals the presence of a tumor involving parts of the left temporal lobe. In addition to certain short-term memory deficits, visual deficits are noted as well. Which of the following is the most likely deficit
- A.
Left homonymous hemianopsia
- B.
Right homonymous hemianopsia
- C.
Left upper quadrantanopia
- D.
Right upper quadrantanopia
- E.
Left lower quadrantanopia
Correct Answer
D. Right upper quadrantanopiaExplanation
From the lateral geniculate nucleus, there are two trajectories that the fiber pathways take en route to the visual cortex. One pathway passes dorsally through the parietal lobe and terminates in the upper bank of the calcarine fissure in the ipsilateral primary visual cortex. The second pathway takes a more circuitous (ventral) route—called the Meyer-Archambault loop—through the temporal lobe and terminates in the lower bank of the calcarine fissure in the ipsilateral primary visual cortex. The lower bank of the calcarine fissure is associated with the upper visual quadrants of the contralateral visual fields for both eyes, while the upper bank of the calcarine fissure is associated with the lower quadrants of the contralateral visual fields for both eyes. Thus, if there is a lesion of the left temporal lobe affecting the Meyer-Archambault loop, then the right upper quadrant for each eye will be affected. This deficit is referred to as a right upper quadrantanopia.Rate this question:
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- 13.
Which of the following types of inhibition have been identified within the dorsal column nuclei?
- A.
Feed-forward inhibition utilizing local interneurons only
- B.
Feedback inhibition utilizing local interneurons only
- C.
Distal inhibition from fibers arising in the cerebral cortex only
- D.
Feed-forward, feedback, and distal inhibition
- E.
Feed-forward and distal inhibition only
Correct Answer
D. Feed-forward, feedback, and distal inhibitionExplanation
To generate an excitatory focus with an inhibitory surround, three types of inhibition are present in the dorsal column nuclei. First-order neurons ascending in the dorsal columns make synaptic contact with different cells in the dorsal column nuclei and excite those cells. One such cell may be an inhibitory interneuron that makes synaptic contact with a neighboring dorsal column nuclear cell, thus inhibiting that cell (i.e., feed-forward inhibition). In addition, the dorsal column cell that is excited by the first-order neuron may make synaptic contact with another inhibitory interneuron (in addition to its classical ascending projection to the ventral posterolateral nucleus of the thalamus). This inhibitory interneuron makes synaptic contact with an adjacent dorsal column cell and inhibits that cell (i.e., feedback inhibition). Finally, a descending fiber from the postcentral gyrus can make synaptic contact with inhibitory interneurons that inhibit dorsal column cells. The figure below illustrates feedback, feed forward, and descending inhibition. Inhibitory neurons are depicted in black.Rate this question:
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- 14.
The terminals of different classes of primary nociceptive afferents have been shown to release which of the following transmitters onto dorsal horn neurons of the spinal cord?
- A.
Enkephalins alone
- B.
Glutamate alone
- C.
Substance P alone
- D.
Glutamate and substance P
- E.
Enkephalins, substance P, and glutamate
Correct Answer
D. Glutamate and substance PExplanation
Primary nociceptive afferent fibers would have to release an excitatory transmitter in order for normal transmission to take place. Two excitatory transmitters have been identified in association with different classes of primary nociceptive afferents: (1) substance P and (2) excitatory amino acids. The best candidate as an excitatory amino acid is glutamate. Since enkephalins have been shown to be inhibitory transmitters in the pain system, they are not likely to be released from the primary afferents. Instead, other CNS neurons impinge upon the primary afferents, and enkephalins are released from those neurons.Rate this question:
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- 15.
Which of the following regions of the cortex is most closely associated with the conscious perception of smell?
- A.
Temporal neocortex
- B.
Posterior parietal lobule
- C.
Cingulate gyrus
- D.
Prefrontal cortex
- E.
Precentral gyrus
Correct Answer
D. Prefrontal cortexExplanation
Experimental evidence indicates the prefrontal cortex is a key region for the conscious perception of smell. This conclusion is based upon two observations. First, the prefrontal cortex receives major inputs from the olfactory bulb by following routes: olfactory bulb to pyriform cortex to prefrontal cortex; or olfactory bulb to pyriform cortex (and olfactory tubercle) to mediodorsal thalamic nucleus to prefrontal cortex. Second, lesions of the prefrontal cortex result in a failure to discriminate odors. Olfactory functions are not known to be associated with any of the other choices. Instead, the primary auditory receiving area is located in the auditory cortex; the posterior parietal lobule is concerned with such processes as the programming mechanisms associated with complex motor tasks; the cingulate gyrus has been associated with such functions as spatial learning and the modulation of autonomic and emotional processes; and the prefrontal gyrus contains the primary motor area.Rate this question:
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- 16.
Cells that respond to an image in a specific position and have discrete excitatory and inhibitory zones and a specific axis of orientation in which a response occurs are classified as which of the following
- A.
M cells of the lateral geniculate nucleus
- B.
P cells of the lateral geniculate nucleus
- C.
Simple cells of the visual cortex
- D.
Complex cells of the visual cortex
- E.
Hypercomplex cells of the visual cortex
Correct Answer
C. Simple cells of the visual cortexExplanation
Cells in the lateral geniculate nucleus respond very much like ganglion cells in the retina because of the point-to-point projection pathway from the retina to the lateral geniculate. Accordingly, lateral geniculate cells have small concentric receptive fields that are either on-center or off-center in which the cells respond best to small spots of light that are in the center of the receptive field. On the other hand, cells in the visual cortex display a much greater complexity in their responses to images in the visual field. Instead of responding to small spots of light, they respond to lines and borders in the different areas of the visual field. In particular, the simple cell responds as a function of the retinal position in which the line-stimulus is located as well as its orientation (e.g., whether it is in a vertical or horizontal position). As a result, when a bar of light is positioned in the appropriate part of the visual field with the appropriate orientation, the cells in area 17 will respond maximally. When either of these parameters is altered, the firing pattern of the cell will be reduced or totally inhibited. Complex cells lack clear excitatory and inhibitory zones (i.e., these neurons respond to bars of light in a given orientation but they are not position-specific). Hypercomplex cells are stimulated by bars of light of specific lengths or by specific shapes.Rate this question:
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- 17.
The neural basis of olfactory discrimination is believed to utilize which of the following?
- A.
Specific activation of different cell groups within the amygdala
- B.
Specific activation of different groups of olfactory glomeruli that are spatially organized and segregated within the olfactory bulb
- C.
Specific activation of different groups of cells within the olfactory tubercle
- D.
Temporal summation of olfactory signals in the anterior olfactory nucleus
- E.
Temporal summation of olfactory signals in the mediodorsal thalamic nucleus
Correct Answer
B. Specific activation of different groups of olfactory glomeruli that are spatially organized and segregated within the olfactory bulbExplanation
A number of recent studies have indicated that different olfactory glomeruli respond to different kinds of olfactory stimuli. In a sense, this represents a type of organization of the olfactory bulb that bears a functional similarity to the spatial organization that exists for other sensory systems. There is no evidence that such a spatial arrangement exists for other components of the olfactory system, nor is there any evidence that temporal summation plays any role in the process of olfactory discrimination.Rate this question:
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- 18.
Which of the following sensory systems is able to utilize a circuit that bypasses the thalamus for the transmission of sensory information from the periphery to the cerebral cortex?
- A.
Conscious proprioception
- B.
Taste
- C.
Olfaction
- D.
Vision
- E.
Audition
Correct Answer
C. OlfactionExplanation
The pathway for conscious proprioception from the body utilizes the ventral posterolateral nucleus as its thalamic relay. Conscious proprioception from the head utilizes the ventral posteromedial nucleus as its relay. The taste pathway utilizes the ventral posteromedial nucleus as well. The visual system utilizes the lateral geniculate nucleus, and the auditory system utilizes the medial geniculate nucleus. In contrast, the olfactory system can transmit olfactory information to the prefrontal cortex without engaging thalamic nuclei. Thus, olfactory information reaches the pyriform cortex and amygdala from the olfactory bulb and then is transmitted directly to the prefrontal cortex. However, it should be noted that olfactory information also can reach the prefrontal cortex by virtue of projections from the olfactory tubercle and pyriform cortex via the mediodorsal thalamic nucleus. Thus, the olfactory system may utilize a parallel processing mechanism in transmitting inputs to the prefrontal cortex.Rate this question:
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- 19.
A patient delays initiation of movement, displays an uneven trajectory in moving her hand from above her head to touch her nose, and is uneven in her attempts to demonstrate rapid alternation of pronating and supernating movements of the hand and forearm. Which of the following is the most likely locus of the lesion
- A.
Hemispheres of the posterior cerebellar lobe
- B.
Flocculonodular lobe of the cerebellum
- C.
Vermal region of the anterior cerebellar lobe
- D.
Fastigial nucleus
- E.
Ventral spinocerebellar tract
Correct Answer
A. Hemispheres of the posterior cerebellar lobeExplanation
The classic appearance of a patient with a lesion of the cerebellar hemispheres is one in which voluntary and skilled movements are affected. They are uncoordinated and there are errors in the range, force, and direction of movement. The relationships between the cerebellum and the motor regions of the cerebral cortex have been disrupted. Lesions of other regions such as the flocculonodular lobe, vermal region of the anterior cerebellar cortex, or fastigial nucleus produce different symptoms (disturbances of balance, muscle tone, or nystagmus). Although pure lesions limited to the ventral spinocerebellar tract have not been reported, it is likely that such a lesion could not account for the symptoms indicated in this question. Information carried by this tract concerns activity of Golgi tendon organs of muscles of the lower limbs.Rate this question:
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- 20.
In studying the functional relationships between the motor cortex and the spinal cord, which of the following effects of cortical stimulation on synaptic potentials would an investigator be likely to observe
- A.
The largest potentials would be seen in spinal motor neurons that innervate proximal muscles
- B.
The largest potentials would be seen in spinal motor neurons that innervate distal muscles
- C.
The potentials seen in spinal motor neurons that innervate proximal and distal muscles would be approximately equivalent
- D.
The largest potentials would be seen in spinal sensory neurons that carry information from spindle afferents to the cerebellum
- E.
The largest potentials would be seen in spinal sensory neurons that carry information from proprioceptors to the thalamus
Correct Answer
B. The largest potentials would be seen in spinal motor neurons that innervate distal musclesExplanation
The largest synaptic potentials produced by cortical stimulation would most likely be seen in spinal motor neurons that innervate distal muscles. One of the primary functions of the corticospinal tract is to control the distal muscles of the hands and fingers. Penfield and others constructed a homuncular map from stimulation studies of the cortex. Such studies reveal that the region of the cortex that is associated with the hands and fingers is considerably larger than those regions that are associated with the proximal musculature. Accordingly, stimulation of the hand region of the cortex would activate more fibers than other cortical regions. It is likely that more ventral horn neurons (located in a lateral position) innervate distal musculature than neurons (located in a medial position) innervate proximal musculature. Since the size of the synaptic potential is a function of both the number of fibers that provide a converging input into a given region and the number of cells that discharge in response to that converging input, it is reasonable to conclude that the largest potentials would be observed following stimulation of the cortical regions associated with the distal musculature. Since neurons situated in the motor cortex project their axons to motor horn cells and interneurons but not to sensory neurons of the dorsal horn (although the component of the corticospinal tract that arises from the parietal lobe does project to the dorsal horn), stimulation of the motor cortex could only produce weak potentials at best among sensory neurons in the dorsal horn.Rate this question:
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- 21.
Paralysis of the right side of the lower face, right spastic paralysis of the limbs, deviation of the tongue to the right with no atrophy, and no loss of taste from any region of the tongue will likely result from a lesion of which of the following?
- A.
Internal capsule of the right side
- B.
Internal capsule of the left side
- C.
Right pontine tegmentum
- D.
Base of the medulla on the right side
- E.
Base of the medulla on the left side
Correct Answer
B. Internal capsule of the left sideExplanation
This constellation of deficits, including paralysis of the lower right face, paralysis of the right lower limbs, and right deviation of the tongue, requires a lesion located in the left internal capsule. Since the motor fibers from the cortex that supply all three of these regions (i.e., limbs, lower face, and tongue) are all crossed, a lesion of the internal capsule will produce each of these deficits. Also, recall that the tongue will deviate to the side of the lesion when the lesion affects the lower motor neuron (LMN) (i.e., cranial nerve XII) directly. When it affects the UMN (i.e., fibers in the internal capsule), inputs into the contralateral nucleus of cranial nerve XII are affected. Thus, the tongue in this instance will deviate to the side opposite the lesion. A lesion of the pontine tegmentum will not affect descending corticospinal or corticomedullary fibers since these fibers are contained in the basilar part of the pons. A lesion of the medulla would be too caudal to affect cortical fibers that terminate on cells of the facial nucleus whose axons innervate muscles of the lower face.Rate this question:
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- 22.
Damage to the subthalamic nucleus will result in which of the following
- A.
Torsion dystonia
- B.
Tremor at rest
- C.
Hemiballism
- D.
Spastic paralysis
- E.
Tardive dyskinesia
Correct Answer
C. HemiballismExplanation
A lesion of the subthalamic nucleus results in hemiballism, a form of dyskinesia in which the patient displays severe involuntary movements. It is believed to occur as a result of an imbalance in the output signals of the basal ganglia. There is a change in the relationship between efferent pathways associated with the two pallidal segments (i.e., a direct pathway from the medial pallidal segment to the VL and VA nuclei of the thalamus versus an indirect pathway, involving connections between the lateral pallidal segment, subthalamic nucleus, and substantia nigra). Thus, in hemiballism the indirect pathway is disrupted, resulting in a change in the output signals of the pallidum to the thalamus.Rate this question:
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- 23.
Which of the following drugs ameliorate choreiform movements?
- A.
ACh blockers because there is an excess of this transmitter in the caudate nucleus
- B.
Dopamine blockers because there is too low a ratio of ACh to dopamine in the neostriatum
- C.
Serotonin blockers because there is too low a ratio of serotonin to ACh and dopamine in the neostriatum
- D.
Substance P antagonists because the ratio of substance P to ACh is too high in the neostriatum
- E.
Norepinephrine antagonists because the ratio of norepinephrine to ACh is too high in the subthalamic nucleus
Correct Answer
B. Dopamine blockers because there is too low a ratio of ACh to dopamine in the neostriatumExplanation
Choreiform movements have generally been associated with damage to the neostriatum (the cortex and the globus pallidus have occasionally been implicated). Normally, there is a balance in what seems to be opposing effects of ACh, dopamine, and GABA in the neostriatum. In this disorder, the levels of ACh and GABA are significantly reduced. This creates an imbalance in which dopamine levels now become (relatively) too high. Accordingly, effective pharmacologic treatment involves the use of dopamine receptor blockers.Rate this question:
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- 24.
Tardive dyskinesia is most likely the result of which of the following
- A.
A change in serotonin receptors that causes a hypersensitivity to serotonin
- B.
A change in ACh receptors that causes a hypersensitivity to ACh
- C.
A change in enkephalin receptors that causes a hypersensitivity to enkephalin
- D.
A change in dopamine receptors that causes a hypersensitivity to dopamine
- E.
A change in GABA receptors that causes a hypersensitivity to GABA
Correct Answer
D. A change in dopamine receptors that causes a hypersensitivity to dopamineExplanation
Tardive dyskinesia, a disorder involving involuntary movements of the mouth, face, and tongue, is caused by long-term treatment with antipsychotic drugs that block or decrease dopaminergic synaptic transmission. Such treatment eventually produces a hypersensitivity in dopamine receptors to dopamine. An imbalance is created between dopamine, GABA, and cholinergic systems within the striatum and this is believed to be responsible for the disorder.Rate this question:
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- 25.
The dorsal spinocerebellar tract, the ventral spinocerebellar tract, and the cuneocerebellar tract, in a general sense, show convergence in their projections to the cerebellum. Which of the following is the principal region within the cerebellum where these fibers converge
- A.
Anterior lobe
- B.
Posterior lobe
- C.
Flocculonodular lobe
- D.
Fastigial nucleus
- E.
Dentate nucleus
Correct Answer
A. Anterior lobeExplanation
One of the most important features of the anterior lobe of the cerebellum is that it receives major inputs from structures that mediate information concerning muscle spindle and Golgi tendon organ activity (sometimes referred to as unconscious proprioception). The pathways that mediate unconscious proprioception include the dorsal and ventral spinocerebellar tracts and the cuneocerebellar tract. Accordingly, the cerebellar anterior lobe is sometimes referred to as the spinocerebellum. The fastigial and dentate nuclei receive their principal inputs from the cerebellar cortex, and their axons project out of the cerebellum. The posterior lobe receives few, if any, inputs from pathways that mediate unconscious proprioception information.Rate this question:
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- 26.
The superior temporal gyrus receives primary inputs from which of the following?
- A.
Centromedian thalamic nucleus
- B.
Medial geniculate thalamic nucleus
- C.
Lateral geniculate thalamic nucleus
- D.
Dorsomedial thalamic nucleus
- E.
Anterior thalamic nucleus
Correct Answer
B. Medial geniculate thalamic nucleusExplanation
The superior temporal gyrus is the primary auditory receiving area in the cerebral cortex. Accordingly, the primary afferent source to this region arises from the medial geniculate nucleus, which constitutes a specific thalamic relay for processing of auditory information.Rate this question:
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- 27.
Of the following thalamic nuclei, which nucleus contains neurons that have properties of both specific and nonspecific thalamus?
- A.
Medial geniculate thalamic nucleus
- B.
Lateral geniculate thalamic nucleus
- C.
Dorsomedial thalamic nucleus
- D.
Anterior thalamic nucleus
- E.
VA thalamic nucleus
Correct Answer
E. VA thalamic nucleusExplanation
The VA nucleus has properties of both the specific and nonspecific thalamus. By this, it is meant that, on the one hand, the VA nucleus receives motor inputs from the basal ganglia, including the substantia nigra, and projects its axons to an important motor region of the brain—the premotor cortex. In this context, the VA nucleus functions as a relay nucleus for the transmission of information associated with motor functions. On the other hand, the VA nucleus also receives various inputs from other thalamic nuclei (such as the centromedian nucleus) and projects its axons in a widespread manner to other parts of the frontal lobe, including the prefrontal cortex. In this context, the VA nucleus can modulate a wide variety of neurons in the cerebral cortex, both directly and indirectly, which is characteristic of nonspecific thalamic nuclei.Rate this question:
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- 28.
Rapid eye movement (REM) sleep is characterized by which of the following?
- A.
Slow-wave EEGs
- B.
Sleep spindles
- C.
Low-voltage EEGs
- D.
High-voltage biphasic waves
- E.
An increase in most skeletal muscle tone
Correct Answer
C. Low-voltage EEGsExplanation
REM sleep is characterized by a low-voltage EEG pattern typical of an alert person. For this reason, REM sleep is sometimes referred to as paradoxical sleep. Other EEG patterns, such as slow waves, high-voltage EEGs, and sleep spindles, occur at other stages of sleep. In addition, REM sleep is characterized by a general loss of skeletal muscle tone with the exception of the eye muscles, which govern the REMs.Rate this question:
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- 29.
While the hippocampal formation has few if any direct (monosynaptic) connections with the lateral hypothalamus, it is known to modulate functions associated with the hypothalamus. The underlying anatomic substrate for such effects is mediated via a synaptic relay in which of the following
- A.
Cingulate gyrus
- B.
Habenular nucleus
- C.
Mediodorsal thalamic nucleus
- D.
Septal area
- E.
Bed nucleus of the stria terminalis
Correct Answer
D. Septal areaExplanation
A major target of efferent fibers from the hippocampal formation is the septal area. Fibers located in the precommissural fornix supply the septal area in an extensive and topographical manner. In turn, the septal area projects significant numbers of fibers to the lateral (and medial) regions of the hypothalamus. In this manner, the septal area serves as a relay for the transmission of signals from the hippocampal formation to the hypothalamus. The hippocampal formation does not project to the habenular nuclei, mediodorsal nucleus, or the bed nucleus of the stria terminalis. Moreover, the cingulate gyrus does not project directly to the hypothalamus.Rate this question:
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- 30.
The vertebral angiogram in the figure below reveals the effects of a severe motorcycle accident upon a 21-year-old woman. As a result of the accident, she most likely suffers from which of the following?
- A.
A UMN paralysis of the right side of the body
- B.
A right homonymous hemianopsia
- C.
A left upper quadrantanopia
- D.
Aphasia
- E.
Dyskinesia
Correct Answer
B. A right homonymous hemianopsiaExplanation
An arterial occlusion compromised the blood supply to the occipital lobe on the left side of the brain. Therefore, it would result in a right homonymous hemianopsia with no motor deficits (since no motor regions of the brain are affected).Rate this question:
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- 31.
. The MRI scan in the figure below reveals a large chromophobe adenoma (T) of the pituitary that impinges on the adjoining brain tissue. This tumor caused which of the following?
- A.
Binasal hemianopsia
- B.
Bitemporal hemianopsia
- C.
Loss of the accommodation reflex
- D.
Loss of the pupillary light reflex
- E.
Loss of conjugate gaze
Correct Answer
B. Bitemporal hemianopsiaExplanation
This large pituitary tumor is seen to compress the optic chiasm. Damage to the chiasm affects the crossing fibers of the nasal retina, which convey information from the temporal visual fields. This results in a bitemporal hemianopsia. Since some parts of the optic nerves are spared, pupillary reflexes are preserved. The neuroanatomic substrates for conjugate gaze (i.e., frontal eye fields; pontine gaze center; medial longitudinal fasciculus; and nuclei of cranial nerves III, IV, and VI) are unaffected by the tumor; the mechanism of conjugate gaze remains intact.Rate this question:
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- 32.
. A 68-year-old man goes to a sleep clinic after he has repeated episodes of loud snoring during sleep coupled with sudden periods of restlessness and cessation of breathing. After extensive analysis, the physicians concluded that the patient's problem was not a result of obstructive sleep. Instead, it was judged that this condition reflected central sleep apnea due to loss of chemoreceptor sensitivity of the neuronal control mechanisms governing respiration. Which of the following sites within the CNS is most closely associated with these effects?
- A.
Dorsal horn of the thoracic spinal cord
- B.
Reticular formation of the medulla
- C.
Midbrain periaqueductal gray
- D.
Hippocampal formation
- E.
Border of occipital and parietal lobes
Correct Answer
B. Reticular formation of the medullaExplanation
Sleep apnea can occur for several reasons. One common basis is an obstruction of the airways (called obstructive sleep apnea). In this case, as indicated in the statement of the question, the physicians ruled out this possibility. Another possible cause involves central sleep apnea. This is due to disruption of the mechanism involving chemoreceptors in the carotid body that monitors carbon dioxide and oxygen levels in the blood. Axons in the carotid body project via the glossopharyngeal nerve (IX) to the reticular formation of the medulla. Therefore, disturbances involving the carotid body could result in central sleep apnea. Here, inappropriate signals are sent to the medullary reticular formation, which, in part, projects caudally to ventral horn sites in the spinal cord, governing such muscles as those that regulate the diaphragm and, therefore, disrupt the normal breathing process.Rate this question:
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- 33.
Loss of cells in which region in the figure below results in a loss of vision in the lower visual field?
- A.
A
- B.
B
- C.
C
- D.
D
- E.
E
Correct Answer
B. BExplanation
This figure is a midsagittal section of the brain. A major portion of the anterior commissure (E) contains fibers that arise from the olfactory bulb and decussate to the contralateral olfactory bulb. The septum pellucidum (G) forms the medial wall of the lateral ventricle, which in fact separates the lateral ventricle on one side from that on the opposite side. The cingulate gyrus (H) is a prominent structure on the medial aspect of the cerebral cortex and constitutes a component of the limbic lobe. It receives a significant input from the anteroventral thalamic nucleus. The major output pathway of the hippocampal formation is the fornix system of fibers (A), which arises from cells in its subicular cortex and adjoining regions of hippocampus. These fibers are then distributed to the anterior thalamic nucleus, mamillary bodies, and septal area. The basilar portion of the pons (D) lies in the ventral half of this region of the brainstem. It receives inputs from each of the lobes of the cerebral cortex, which it then relays to the cerebellar cortex. The primary visual cortex lies on both banks of the calcarine fissure. Cells located on the lower bank receive inputs from the lateral geniculate nucleus that relate to either the nasal or temporal upper visual fields. Therefore, a lesion of this region would produce an upper quadrantanopia (i.e., loss of one-quarter of the visual field). The corpus callosum constitutes the major channel by which the cerebral cortex on one side can communicate with the cortex of the opposite side. The genu of the corpus callosum (F) contains fibers that pass from the frontal lobe of one side to that of the other.Rate this question:
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- 34.
Damage to which region in the figure below, unilaterally will produce an upper quadrantanopia?
- A.
A
- B.
B
- C.
C
- D.
D
- E.
E
Correct Answer
C. CExplanation
Damage to region C unilaterally will produce an upper quadrantanopia. This means that if the region C is damaged on one side of the brain, the person will lose vision in the upper quadrant of the visual field on the opposite side. This can occur due to a stroke or injury affecting the visual pathway in the brain.Rate this question:
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- 35.
Damage to which structure in the figure below could produce both a medial gaze paralysis and failure of pupillary constriction?
- A.
A
- B.
B
- C.
C
- D.
D
- E.
E
Correct Answer
B. BExplanation
This figure is a ventral view of the brainstem. Fibers that arise from the nucleus ambiguus exit the brain on the lateral side of the medulla as part of the vagus nerve (K) and innervate the muscles of the larynx and pharynx as special visceral efferents. The motor root (H) lies medial to the sensory root and innervates the muscles of mastication. The mamillary bodies (A), which lie on the ventral surface of the brain at the caudal aspect of the hypothalamus, project many of their axons to the anteroventral thalamic nucleus as the mamillothalamic tract. The facial nerve (C) exits the brain at the level of the ventrolateral aspect of the caudal pons and its special visceral efferent component innervates the muscles of facial expression.
The cerebral peduncle (G) is situated in the ventrolateral aspect of the midbrain and contains fibers of cortical origin that project to all levels of the neuraxis of the brainstem and spinal cord. Note that the selection of choice E, the pyramids, would not have been a correct choice since the fibers present at this level can only terminate within the medulla or spinal cord. First-order somatosensory fibers from the region of the face (I) enter the brain laterally at the level of the middle of the pons as the sensory root of the trigeminal nerve. The oculomotor nerve (B) exits the brain at the level of the ventromedial aspect of the midbrain and some fibers of the general somatic efferent component of this nerve innervate the medial rectus. Damage to this component results in a loss of ability for medial gaze. Another component of the oculomotor nerve, the GVE component, constitutes the preganglionic parasympathetic neuron in a disynaptic pathway whose postganglionic division innervates the pupillary constrictor muscles. Accordingly, damage to the preganglionic division results in loss of pupillary constriction, which normally occurs in the presence of light as well as in accommodation. The abducens nerve (J) exits the brain at a ventromedial position at the level of the medulla-pontine border, and its fibers innervate the lateral rectus muscle. Damage to this nerve results in a lateral gaze paralysis.
The optic chiasm (F) contains fibers that cross over to reach the lateral geniculate nucleus on the side contralateral to the retina from which they originated. Such fibers are associated with the temporal (i.e., lateral) visual fields. Therefore, damage to the optic chiasm will cause blindness in the lateral half of each of the visual fields. Such a deficit is referred to as bitemporal hemianopsia. First-order neurons from the labyrinth organs (i.e., semicircular canals, saccule, and utricle) convey information concerning the position of the head in space along the vestibular component of the eighth nerve into the central nervous system. This nerve enters the brain laterally at the level of the upper medulla. The hypoglossal nerve (L) exits the brain at the level of the middle of the medulla between the pyramid and the olive. These fibers innervate muscles that move the tongue toward the opposite side. For this reason, a lesion of the hypoglossal nucleus or its nerve will result in a deviation of the tongue to the side of the lesion because of the unopposed action of the contralateral hypoglossal nerve, which remains intact.Rate this question:
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- 36.
Damage to which structure in the figure below produces a lateral gaze paralysis?
- A.
F
- B.
G
- C.
H
- D.
I
- E.
J
Correct Answer
E. JExplanation
This figure is a ventral view of the brainstem. Fibers that arise from the nucleus ambiguus exit the brain on the lateral side of the medulla as part of the vagus nerve (K) and innervate the muscles of the larynx and pharynx as special visceral efferents. The motor root (H) lies medial to the sensory root and innervates the muscles of mastication. The mamillary bodies (A), which lie on the ventral surface of the brain at the caudal aspect of the hypothalamus, project many of their axons to the anteroventral thalamic nucleus as the mamillothalamic tract. The facial nerve (C) exits the brain at the level of the ventrolateral aspect of the caudal pons and its special visceral efferent component innervates the muscles of facial expression.
The cerebral peduncle (G) is situated in the ventrolateral aspect of the midbrain and contains fibers of cortical origin that project to all levels of the neuraxis of the brainstem and spinal cord. Note that the selection of choice E, the pyramids, would not have been a correct choice since the fibers present at this level can only terminate within the medulla or spinal cord. First-order somatosensory fibers from the region of the face (I) enter the brain laterally at the level of the middle of the pons as the sensory root of the trigeminal nerve. The oculomotor nerve (B) exits the brain at the level of the ventromedial aspect of the midbrain and some fibers of the general somatic efferent component of this nerve innervate the medial rectus. Damage to this component results in a loss of ability for medial gaze. Another component of the oculomotor nerve, the GVE component, constitutes the preganglionic parasympathetic neuron in a disynaptic pathway whose postganglionic division innervates the pupillary constrictor muscles. Accordingly, damage to the preganglionic division results in loss of pupillary constriction, which normally occurs in the presence of light as well as in accommodation. The abducens nerve (J) exits the brain at a ventromedial position at the level of the medulla-pontine border, and its fibers innervate the lateral rectus muscle. Damage to this nerve results in a lateral gaze paralysis.
The optic chiasm (F) contains fibers that cross over to reach the lateral geniculate nucleus on the side contralateral to the retina from which they originated. Such fibers are associated with the temporal (i.e., lateral) visual fields. Therefore, damage to the optic chiasm will cause blindness in the lateral half of each of the visual fields. Such a deficit is referred to as bitemporal hemianopsia. First-order neurons from the labyrinth organs (i.e., semicircular canals, saccule, and utricle) convey information concerning the position of the head in space along the vestibular component of the eighth nerve into the central nervous system. This nerve enters the brain laterally at the level of the upper medulla. The hypoglossal nerve (L) exits the brain at the level of the middle of the medulla between the pyramid and the olive. These fibers innervate muscles that move the tongue toward the opposite side. For this reason, a lesion of the hypoglossal nucleus or its nerve will result in a deviation of the tongue to the side of the lesion because of the unopposed action of the contralateral hypoglossal nerve, which remains intact.Rate this question:
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- 37.
In the figure below, disruption of fibers at which site resulting from a tumor would likely produce a bitemporal hemianopsia?
- A.
C
- B.
D
- C.
E
- D.
F
- E.
G
Correct Answer
D. FExplanation
This figure is a ventral view of the brainstem. Fibers that arise from the nucleus ambiguus exit the brain on the lateral side of the medulla as part of the vagus nerve (K) and innervate the muscles of the larynx and pharynx as special visceral efferents. The motor root (H) lies medial to the sensory root and innervates the muscles of mastication. The mamillary bodies (A), which lie on the ventral surface of the brain at the caudal aspect of the hypothalamus, project many of their axons to the anteroventral thalamic nucleus as the mamillothalamic tract. The facial nerve (C) exits the brain at the level of the ventrolateral aspect of the caudal pons and its special visceral efferent component innervates the muscles of facial expression.
The cerebral peduncle (G) is situated in the ventrolateral aspect of the midbrain and contains fibers of cortical origin that project to all levels of the neuraxis of the brainstem and spinal cord. Note that the selection of choice E, the pyramids, would not have been a correct choice since the fibers present at this level can only terminate within the medulla or spinal cord. First-order somatosensory fibers from the region of the face (I) enter the brain laterally at the level of the middle of the pons as the sensory root of the trigeminal nerve. The oculomotor nerve (B) exits the brain at the level of the ventromedial aspect of the midbrain and some fibers of the general somatic efferent component of this nerve innervate the medial rectus. Damage to this component results in a loss of ability for medial gaze. Another component of the oculomotor nerve, the GVE component, constitutes the preganglionic parasympathetic neuron in a disynaptic pathway whose postganglionic division innervates the pupillary constrictor muscles. Accordingly, damage to the preganglionic division results in loss of pupillary constriction, which normally occurs in the presence of light as well as in accommodation. The abducens nerve (J) exits the brain at a ventromedial position at the level of the medulla-pontine border, and its fibers innervate the lateral rectus muscle. Damage to this nerve results in a lateral gaze paralysis.
The optic chiasm (F) contains fibers that cross over to reach the lateral geniculate nucleus on the side contralateral to the retina from which they originated. Such fibers are associated with the temporal (i.e., lateral) visual fields. Therefore, damage to the optic chiasm will cause blindness in the lateral half of each of the visual fields. Such a deficit is referred to as bitemporal hemianopsia. First-order neurons from the labyrinth organs (i.e., semicircular canals, saccule, and utricle) convey information concerning the position of the head in space along the vestibular component of the eighth nerve into the central nervous system. This nerve enters the brain laterally at the level of the upper medulla. The hypoglossal nerve (L) exits the brain at the level of the middle of the medulla between the pyramid and the olive. These fibers innervate muscles that move the tongue toward the opposite side. For this reason, a lesion of the hypoglossal nucleus or its nerve will result in a deviation of the tongue to the side of the lesion because of the unopposed action of the contralateral hypoglossal nerve, which remains intact.Rate this question:
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- 38.
A lesion of which nerve shown in the figure below will cause the tongue to deviate to the side of the lesion?
- A.
H
- B.
I
- C.
J
- D.
K
- E.
L
Correct Answer
E. LExplanation
This figure is a ventral view of the brainstem. Fibers that arise from the nucleus ambiguus exit the brain on the lateral side of the medulla as part of the vagus nerve (K) and innervate the muscles of the larynx and pharynx as special visceral efferents. The motor root (H) lies medial to the sensory root and innervates the muscles of mastication. The mamillary bodies (A), which lie on the ventral surface of the brain at the caudal aspect of the hypothalamus, project many of their axons to the anteroventral thalamic nucleus as the mamillothalamic tract. The facial nerve (C) exits the brain at the level of the ventrolateral aspect of the caudal pons and its special visceral efferent component innervates the muscles of facial expression.
The cerebral peduncle (G) is situated in the ventrolateral aspect of the midbrain and contains fibers of cortical origin that project to all levels of the neuraxis of the brainstem and spinal cord. Note that the selection of choice E, the pyramids, would not have been a correct choice since the fibers present at this level can only terminate within the medulla or spinal cord. First-order somatosensory fibers from the region of the face (I) enter the brain laterally at the level of the middle of the pons as the sensory root of the trigeminal nerve. The oculomotor nerve (B) exits the brain at the level of the ventromedial aspect of the midbrain and some fibers of the general somatic efferent component of this nerve innervate the medial rectus. Damage to this component results in a loss of ability for medial gaze. Another component of the oculomotor nerve, the GVE component, constitutes the preganglionic parasympathetic neuron in a disynaptic pathway whose postganglionic division innervates the pupillary constrictor muscles. Accordingly, damage to the preganglionic division results in loss of pupillary constriction, which normally occurs in the presence of light as well as in accommodation. The abducens nerve (J) exits the brain at a ventromedial position at the level of the medulla-pontine border, and its fibers innervate the lateral rectus muscle. Damage to this nerve results in a lateral gaze paralysis.
The optic chiasm (F) contains fibers that cross over to reach the lateral geniculate nucleus on the side contralateral to the retina from which they originated. Such fibers are associated with the temporal (i.e., lateral) visual fields. Therefore, damage to the optic chiasm will cause blindness in the lateral half of each of the visual fields. Such a deficit is referred to as bitemporal hemianopsia. First-order neurons from the labyrinth organs (i.e., semicircular canals, saccule, and utricle) convey information concerning the position of the head in space along the vestibular component of the eighth nerve into the central nervous system. This nerve enters the brain laterally at the level of the upper medulla. The hypoglossal nerve (L) exits the brain at the level of the middle of the medulla between the pyramid and the olive. These fibers innervate muscles that move the tongue toward the opposite side. For this reason, a lesion of the hypoglossal nucleus or its nerve will result in a deviation of the tongue to the side of the lesion because of the unopposed action of the contralateral hypoglossal nerve, which remains intact.Rate this question:
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- 39.
After an individual is admitted to the hospital, it is determined that he displays a variable weakness of cranial nerve and limb muscles but shows no clinical signs of denervation from tests, which include electromyogram (EMG) recordings. This disorder was partially reversed by the administration of drugs that inhibit acetylcholinesterase. Which of the following is the most likely diagnosis?
- A.
Multiple sclerosis (MS)
- B.
Amyotrophic lateral sclerosis (ALS)
- C.
Myasthenia gravis
- D.
Combined system disease
- E.
Muscular dystrophy (MD)
Correct Answer
C. Myasthenia gravisExplanation
Myasthenia gravis is an autoimmune disease that causes cranial nerve and limb muscle weakness by producing antibodies that act against the nicotinic receptor at the neuromuscular junction. The result is that the action of nerve fibers that innervate skeletal muscle are affected, producing loss of the effects of ACh at the neuromuscular junction. The net result is a reduction of the size of the action potential in the muscle, producing a weakness in the affected muscle. This disorder is reversed by administration of drugs that inhibit the enzyme, acetylcholinesterase, that degrades ACh. Multiple sclerosis, ALS, and combined system disease (see the chapter entitled "The Spinal Cord") involve damage to axons and/or nerve cells within the CNS, producing much more profound damage to motor functions and, in the case of combined system disease, damage to both motor and sensory systems. Muscular dystrophy is typically characterized, in part, by progressive weakness of muscles and degeneration of the muscle fibers. The other disorders listed all involve disorders affecting the CNS, and thus, the symptoms associated with these disorders differ significantly from those described in this case. Excessive release of ACh is not a realistic event that is likely to occur (except from the bite of a black widow spider). In theory, if it were to occur, there is no reason to believe that muscular weakness would be a symptom. Instead, there would be some rigidity and muscle spasms.Rate this question:
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- 40.
An individual is admitted to the emergency room of a hospital after taking a drug of abuse that destroyed selective groups of neurons in the brainstem. After the individual became ambulatory, he became chronically depressed. Which of the following neuronal groups in the brainstem might be related, either directly or indirectly, to this person's condition?
- A.
Vestibular nuclei
- B.
Nucleus ambiguus
- C.
Trigeminal spinal nucleus
- D.
Dorsal column nuclei
- E.
Raphe nuclei
Correct Answer
E. Raphe nucleiExplanation
There is an increasing body of evidence that reductions in serotonin levels play an important role in depressive disorders. The raphe neurons, located along the midline of the brainstem, provide the basic sites of serotonergic neurons that project to all parts of the brain and spinal cord. The other choices refer to structures that concern motor and/or sensory functions mainly associated with cranial nerves. Since the raphe neurons were damaged, the neurotransmitter most likely responsible for the onset of depression in this instance is serotonin. It is possible that other transmitter systems, such as the catecholamines, may also play a role in this disorder; however, they would not be chiefly responsible for the disorder in this instance because of the restricted locus of the lesion. Recent practice has been to treat depression with serotonin reuptake inhibitors such as fluoxetine (Prozac), which has been found to be effective after several weeks of treatment. The other choices for question 102 would be inappropriate because they would likely have a depressant effect on CNS functions.Rate this question:
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- 41.
An individual is admitted to the emergency room of a hospital after taking a drug of abuse that destroyed selective groups of neurons in the brainstem. After the individual became ambulatory, he became chronically depressed. The neurotransmitter loss most likely linked to the symptoms is which of the following?
- A.
Enkephalin
- B.
Dopamine
- C.
Norepinephrine
- D.
Serotonin
- E.
Glycine
Correct Answer
D. SerotoninExplanation
There is an increasing body of evidence that reductions in serotonin levels play an important role in depressive disorders. The raphe neurons, located along the midline of the brainstem, provide the basic sites of serotonergic neurons that project to all parts of the brain and spinal cord. The other choices refer to structures that concern motor and/or sensory functions mainly associated with cranial nerves. Since the raphe neurons were damaged, the neurotransmitter most likely responsible for the onset of depression in this instance is serotonin. It is possible that other transmitter systems, such as the catecholamines, may also play a role in this disorder; however, they would not be chiefly responsible for the disorder in this instance because of the restricted locus of the lesion. Recent practice has been to treat depression with serotonin reuptake inhibitors such as fluoxetine (Prozac), which has been found to be effective after several weeks of treatment. The other choices for question 102 would be inappropriate because they would likely have a depressant effect on CNS functions.Rate this question:
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- 42.
An individual is admitted to the emergency room of a hospital after taking a drug of abuse that destroyed selective groups of neurons in the brainstem. After the individual became ambulatory, he became chronically depressed. An accepted approach toward the treatment of this disorder would be to administer which of the following?
- A.
A serotonin reuptake inhibitor (SSRI)
- B.
A CNS depressant
- C.
A dopaminergic antagonist
- D.
A noradrenergic antagonist
- E.
An NMDA blocker
Correct Answer
A. A serotonin reuptake inhibitor (SSRI)Explanation
There is an increasing body of evidence that reductions in serotonin levels play an important role in depressive disorders. The raphe neurons, located along the midline of the brainstem, provide the basic sites of serotonergic neurons that project to all parts of the brain and spinal cord. The other choices refer to structures that concern motor and/or sensory functions mainly associated with cranial nerves. Since the raphe neurons were damaged, the neurotransmitter most likely responsible for the onset of depression in this instance is serotonin. It is possible that other transmitter systems, such as the catecholamines, may also play a role in this disorder; however, they would not be chiefly responsible for the disorder in this instance because of the restricted locus of the lesion. Recent practice has been to treat depression with serotonin reuptake inhibitors such as fluoxetine (Prozac), which has been found to be effective after several weeks of treatment. The other choices for question 102 would be inappropriate because they would likely have a depressant effect on CNS functions.Rate this question:
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- 43.
An elderly individual is admitted to a hospital after a long period in which the family had complained that he had showed increasing incidences of disorientation coupled with memory loss. The patient was diagnosed with Alzheimer's disease and a few years later, after further physical and mental deterioration, the patient died. An autopsy was taken of his brain and regional brain chemistry and neuropathology identified. Which of the following is the likely sites where neuropathology was identified?
- A.
Cerebellar cortex, hypothalamus, red nucleus
- B.
Substantia nigra, midbrain periaqueductal gray, ventrolateral thalamus
- C.
Nucleus gracilis, deep pontine nuclei, vestibular nuclei
- D.
Cerebral cortex, basal nucleus of Meynert, hippocampus
- E.
Fastigial nucleus, subthalamic nucleus, superior colliculus
Correct Answer
D. Cerebral cortex, basal nucleus of Meynert, hippocampusExplanation
The primary regions shown to be affected by Alzheimer's disease include the basal nucleus of Meynert, (which contains cholinergic neurons that project widely to the forebrain, including the cerebral cortex), the hippocampal formation, and the cerebral cortex. The other choices included structures that have not been significantly implicated in this disorder. The neurotransmitter that has been most implicated in this disorder is ACh. Alzheimer's brains have been shown to have reduced levels of ACh and cholinergic markers, especially after damage to cholinergic neurons of the basal nucleus of Meynert. While reductions in other neurotransmitter levels may also occur, the other choices of neurotransmitters presented have not been clearly implicated in this disorder. One of the clearest neuropathological characteristics of Alzheimer's disease is the presence of amyloid deposits and neurofibrillary tangles in the cerebral cortex. In fact, there has been a new and promising strategy that has been applied for the treatment of Alzheimer's disease. It involves the attempt to administer small molecules that retard the aggregation of amyloid- beta peptides that form fibrillar amyloid plaques, which affect the normal functions of neurons.Rate this question:
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- 44.
An elderly individual is admitted to a hospital after a long period in which the family had complained that he had showed increasing incidences of disorientation coupled with memory loss. The patient was diagnosed with Alzheimer's disease and a few years later, after further physical and mental deterioration, the patient died. An autopsy was taken of his brain and regional brain chemistry and neuropathology identified. Which one of the following neurotransmitters is most often implicated in this disorder with respect to the affected brain regions?
- A.
Histamine
- B.
Substance P
- C.
ACh
- D.
Enkephalin
- E.
Dopamine
Correct Answer
C. AChExplanation
The primary regions shown to be affected by Alzheimer's disease include the basal nucleus of Meynert, (which contains cholinergic neurons that project widely to the forebrain, including the cerebral cortex), the hippocampal formation, and the cerebral cortex. The other choices included structures that have not been significantly implicated in this disorder. The neurotransmitter that has been most implicated in this disorder is ACh. Alzheimer's brains have been shown to have reduced levels of ACh and cholinergic markers, especially after damage to cholinergic neurons of the basal nucleus of Meynert. While reductions in other neurotransmitter levels may also occur, the other choices of neurotransmitters presented have not been clearly implicated in this disorder. One of the clearest neuropathological characteristics of Alzheimer's disease is the presence of amyloid deposits and neurofibrillary tangles in the cerebral cortex. In fact, there has been a new and promising strategy that has been applied for the treatment of Alzheimer's disease. It involves the attempt to administer small molecules that retard the aggregation of amyloid-beta peptides that form fibrillar amyloid plaques, which affect the normal functions of neurons.Rate this question:
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- 45.
An elderly individual is admitted to a hospital after a long period in which the family had complained that he had showed increasing incidences of disorientation coupled with memory loss. The patient was diagnosed with Alzheimer''s disease and a few years later, after further physical and mental deterioration, the patient died. An autopsy was taken of his brain and regional brain chemistry and neuropathology identified. Upon examination of the brain, it was shown that the affected regions displayed which of the following?
- A.
A decrease in substance P in the hypothalamus and brainstem reticular formation
- B.
Marked degeneration of most myelinated pathways
- C.
Amyloid deposits and neurofibrillary tangles
- D.
Marked retrograde degeneration in sensory neurons of the brainstem
- E.
Glial loss associated with the medial lemniscus and spinothalamic pathways
Correct Answer
C. Amyloid deposits and neurofibrillary tanglesExplanation
The primary regions shown to be affected by Alzheimer's disease include the basal nucleus of Meynert, (which contains cholinergic neurons that project widely to the forebrain, including the cerebral cortex), the hippocampal formation, and the cerebral cortex. The other choices included structures that have not been significantly implicated in this disorder. The neurotransmitter that has been most implicated in this disorder is ACh. Alzheimer's brains have been shown to have reduced levels of ACh and cholinergic markers, especially after damage to cholinergic neurons of the basal nucleus of Meynert. While reductions in other neurotransmitter levels may also occur, the other choices of neurotransmitters presented have not been clearly implicated in this disorder. One of the clearest neuropathological characteristics of Alzheimer's disease is the presence of amyloid deposits and neurofibrillary tangles in the cerebral cortex. In fact, there has been a new and promising strategy that has been applied for the treatment of Alzheimer's disease. It involves the attempt to administer small molecules that retard the aggregation of amyloid- peptides that form fibrillar amyloid plaques, which affect the normal functions of neurons.Rate this question:
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- 46.
An elderly individual is admitted to a hospital after a long period in which the family had complained that he had showed increasing incidences of disorientation coupled with memory loss. The patient was diagnosed with Alzheimer's disease and a few years later, after further physical and mental deterioration, the patient died. An autopsy was taken of his brain and regional brain chemistry and neuropathology identified. Of the following, which therapeutic strategy for treatment of this disorder shows promise?
- A.
Surgical removal of selective regions of the cerebral cortex
- B.
Administration of serotonergic agonists that act specifically on cerebral cortical neurons
- C.
Administration of cholinergic antagonists directed against nicotinic receptors in the cerebral cortex
- D.
Administration of noradrenergic agonists directed against alpha2 receptors in the cerebral cortex
- E.
Administration of compounds that slow aggregation of amyloid- beta peptide into its fibrillar form
Correct Answer
E. Administration of compounds that slow aggregation of amyloid- beta peptide into its fibrillar formExplanation
The primary regions shown to be affected by Alzheimer's disease include the basal nucleus of Meynert, (which contains cholinergic neurons that project widely to the forebrain, including the cerebral cortex), the hippocampal formation, and the cerebral cortex. The other choices included structures that have not been significantly implicated in this disorder. The neurotransmitter that has been most implicated in this disorder is ACh. Alzheimer's brains have been shown to have reduced levels of ACh and cholinergic markers, especially after damage to cholinergic neurons of the basal nucleus of Meynert. While reductions in other neurotransmitter levels may also occur, the other choices of neurotransmitters presented have not been clearly implicated in this disorder. One of the clearest neuropathological characteristics of Alzheimer's disease is the presence of amyloid deposits and neurofibrillary tangles in the cerebral cortex. In fact, there has been a new and promising strategy that has been applied for the treatment of Alzheimer's disease. It involves the attempt to administer small molecules that retard the aggregation of amyloid- peptides that form fibrillar amyloid plaques, which affect the normal functions of neurons.Rate this question:
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- 47.
An individual is admitted to the emergency room and is diagnosed as having cortical damage and resultant neuronal degeneration due to an ischemic insult. The neurologist concluded that the brain damage involved neurotoxicity of those cells. The neurotransmitter change associated with neurotoxicity in this case is believed to involve which of the following?
- A.
Extracellular accumulation of norepinephrine
- B.
Extracellular accumulation of ACh
- C.
Extracellular accumulation of glutamate
- D.
Extracellular loss of serotonin
- E.
Extracellular loss of GABA
Correct Answer
C. Extracellular accumulation of glutamateExplanation
It has been discovered that one mechanism of neurodegeneration involves prolonged activation of neurons by glutamate. It is believed that if glutamate accumulates in the extracellular space and is not removed, the presence of glutamate will effectively stimulate the neuron to death. It has been shown that neurotoxicity is linked to cell death after a stroke, which causes brain ischemia and oxygen deprivation. Glutamate receptors are involved in ischemic cell damage in the following way: Glutamate released from the presynaptic terminal would normally activate NMDA and AMPA receptors in the postsynaptic membrane. This results in an increase in the intracellular concentration of Ca2+, which remains long after the initial stimulus is removed, and thus prevents the cell from reestablishing a resting membrane potential. The net effect here is to produce injury (or death) to the cell.Rate this question:
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- 48.
An individual is admitted to the emergency room and is diagnosed as having cortical damage and resultant neuronal degeneration due to an ischemic insult. The neurologist concluded that the brain damage involved neurotoxicity of those cells. The likely mechanism underlying neurotoxicity as a result of ischemia involves which of the following?
- A.
Entry of Ca2+ into the cell
- B.
Reduction of extracellular chloride
- C.
Delayed removal of norepinephrine from the synapse
- D.
Hypersensitivity of the postsynaptic membrane to GABA
- E.
Failure of degradation of ACh
Correct Answer
A. Entry of Ca2+ into the cellExplanation
It has been discovered that one mechanism of neurodegeneration involves prolonged activation of neurons by glutamate. It is believed that if glutamate accumulates in the extracellular space and is not removed, the presence of glutamate will effectively stimulate the neuron to death. It has been shown that neurotoxicity is linked to cell death after a stroke, which causes brain ischemia and oxygen deprivation. Glutamate receptors are involved in ischemic cell damage in the following way: Glutamate released from the presynaptic terminal would normally activate NMDA and AMPA receptors in the postsynaptic membrane. This results in an increase in the intracellular concentration of Ca2+, which remains long after the initial stimulus is removed, and thus prevents the cell from reestablishing a resting membrane potential. The net effect here is to produce injury (or death) to the cell.Rate this question:
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- 49.
A 50-year-old man suffers from anxiety attacks. To treat this disorder, the patient would most likely be treated with which of the following drugs?
- A.
Picrotoxin
- B.
Naloxone
- C.
Chlordiazepoxide
- D.
Bicuculline
- E.
Dopamine
Correct Answer
C. ChlordiazepoxideExplanation
One of the strategies used effectively for the treatment of anxiety disorders is to use classes of drugs that suppress CNS activity. One such class includes benzodiazepine agonists, such as chlordiazepoxide. This drug enhances GABA transmission by binding to the benzodiazepine site on the GABAA-receptor benzodiazepine chloride ionophore complex. In this manner, it acts as a GABA agonist, producing anxiolytic, sedative, and anticonvulsant effects. The other choices for both questions relate to drugs that have opposite effects, namely, ones with excitatory effects on CNS neurons.Rate this question:
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- 50.
A 50-year-old man suffers from anxiety attacks. Which of the following is the mechanism underlying the action of this drug of choice?
- A.
Blockade of chloride channel permeability
- B.
Opioid receptor blockade
- C.
Binding of the drug to the GABA benzodiazepine site
- D.
Activation of muscarinic cholinergic receptor
- E.
Competitive binding of the GABAA-receptor site
Correct Answer
C. Binding of the drug to the GABA benzodiazepine siteExplanation
One of the strategies used effectively for the treatment of anxiety disorders is to use classes of drugs that suppress CNS activity. One such class includes benzodiazepine agonists, such as chlordiazepoxide. This drug enhances GABA transmission by binding to the benzodiazepine site on the GABAA-receptor benzodiazepine chloride ionophore complex. In this manner, it acts as a GABA agonist, producing anxiolytic, sedative, and anticonvulsant effects. The other choices for both questions relate to drugs that have opposite effects, namely, ones with excitatory effects on CNS neurons.Rate this question:
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Apr 17, 2024Quiz Edited by
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Feb 11, 2010Quiz Created by
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