Essential Neuroscience 3rd Ed Siegel and Sapru Quizzes Ch 1, 3, 5, 6, 8-11, 13, 14, 18-20, 22, 25-27

A 68-year-old man is admitted to the emergency room (ER) after initially complaining of dizziness. In the ER, the patient indicated that he could not move his right arm or leg, and his speech was slurred. The tongue was directed to the right side when the patient was asked to protrude it, and the patient's jaw drooped to the right side as well. Sensory functions on each side of the body appeared normal as well as motor functions on the left side. 1. The patient suffered a stroke involving the: a. Anterior cerebral artery b. Middle cerebral artery c. Posterior cerebral artery d. Anterior spinal artery e. Vertebral artery 2. The stroke involved the: a. Right precentral gyrus b. Left postcentral gyrus c. Left internal capsule d. Right internal capsule e. Left medullary pyramids

1. b. Middle cerebral artery 2. c. Left internal capsule The lenticulostriate branches of the middle cerebral artery supply the internal capsule, including the region of the posterior limb and genu. The key point here is that these regions of the internal capsule contain corticobulbar and corticospinal fibers that mediate functions of the head and body that were affected in the patient, likely producing right central palsy. Thus, of the choices given in this question, only the middle cerebral artery is correct because its branches supply these regions and none of the other arteries supply fibers that mediate these functions. Note that both the anterior spinal and vertebral arteries are present at medullary lev- els, whereas the corticobulbar fibers mediating motor control of the jaw exit at the level of the pons. The anterior cerebral artery, which passes on the medial aspect of the cortex, does not sup- ply neurons that mediate speech (located laterally on the cortex). As indicated in the explanation to Question 4, branches of the middle cerebral artery supply descending fibers in the internal capsule, which are associated with the motor functions disrupted in this patient. Other choices involving fiber bundles on the right side of the brain are wrong because the right side of the body was affected in this case, requiring an answer that included damage to the left corticospinal tract. The left post- central gyrus is not directly involved in motor functions, and the left medullary pyramids lie below the level where corticobulbar fibers exit to innervate motor neurons of the facial nerve.

A patient presents with violent involuntary ballistic movements that are jerky and irregular and mainly involve the upper extremity on one side of the body. 1. The lesion was most likely located in the: a. Neostriatum b. Paleostriatum c. Subthalamic nucleus d. Pars reticulata of the substantia nigra e. Claustrum 2. The motor dysfunctions characteristic of this disorder can best be accounted for in terms of loss of: a. Inhibitory input to the caudate nucleus b. Excitatory input to the medial (internal) pallidal segment c. Dopaminergic input to the caudate nucleus and putamen d. Gamma aminobutyric acid (GABA)-ergic input to the lateral (external) pallidal segment e. Glutamatergic input to the caudate nucleus

1. c. Subthalamic nucleus 2. b. Excitatory input to the medial (internal) pallidal segment Hemiballism is associated with a discrete lesion of the subthalamic nucleus. It consists of wild, uncontrolled movements of the distal musculature (limb) on the side contralateral to the site of the lesion. It is believed to constitute a "release" phenomenon in which the pallidalthalamic fibers, which are inhibitory to ventral anterior and ventrolateral nuclei of thalamus, are prevented from discharging due to the loss of excitatory input from the glutamatergic fibers that arise from the subthalamic nucleus and that project to the medial pallidal segment. The other choices for question 1 are not correct for the following reasons. Lesions of the neostriatum are associated with Huntington's disease and other forms of choreiform movements, which can affect both the upper and lower limb. Lesions of the paleostriatum (globus pallidus) have not been associated with hemiballism; likewise, lesions of the pars reticulata of the substantia nigra have not been associated with hemiballism. The claustrum is not linked to motor functions.

A 68yo woman was admitted to the ED after having lost consciousness at her home. Several days after regaining consciousness, a neurologic examination revealed the presence of nystagmus, deviation of the right eye medially, loss of sensation of the right side of the face and pain and temperature sensation from the left side of the body, Horner's syndrome, and some loss of coordination. The neurologist concluded that the patient had suffered a stroke. 1) Where was the most likely location of her stroke? a) bilaterally, at the pontine-midbrain border b) in the right basilar pons c) in the left basilar pons d) in the right pontine tegmentum e) in the left pontine tegmentum 2) Structures affected by the stroke include: a) corticospinal tract, medial lemniscus, spinothalamic tract, middle cerebellar peduncle, trigemniothalamic tracts, and reticular formation of right side of the rostral pons b) Spinothalamic tract, trigeminal structures, medial lemniscus, medial longitudinal fasciculus, cranial nerve VIII, and middle cerebellar peduncle of right side of the caudal half of pons c) Medial longitudinal fasciculus, cranial nerve VI, middle cerebellar peduncle, reticular formation, spinothalamic fibers, and trigeminothalamic structures of right side of caudal half of the pons d) reticular formation of the right pontine tegmentum near the border with the pons e) cerebellum, medial longitudinal fasciculus, medial lemniscus, spinothalamic tract, main sensory nucleus of cranial nerve (CN V), and motor nucleus of CN VII of the right side of the rostral pons

1. d) in the right pontine tegmentum 2. c) Medial longitudinal fasciculus, cranial nerve VI, middle cerebellar peduncle, reticular formation, spinothalamic fibers, and trigeminothalamic structures of right side of caudal half of the pons In order for this constellation of deficits to be present, the lesions must be present in the right pontine tegmentum. The lesion has to be on the right side because the first-order sensory fibers from the head are uncrossed, whereas pain and temperature fibers from the body are crossed. The pontine tegmentum contains these sensory fibers. In addition, it also contains descending sympathetic fibers, the medial longitudinal fasciculus, and the nucleus and fibers of cranial nerve VI, the damage of which would account for the loss of functions described in this case.

A patient presents with reduced facial expression, spontaneous movements (slower than normal) that are revealed most clearly when walking, monotonous speech, an increase in muscle tone in the arms, and a rhythmic tremor (4 to 7 Hz) in the fingers, including a pill-rolling tremor. 3. This disorder can be directly linked to loss of: a) Glutamatergic inputs from neocortex to the neostriatum b) Gamma aminobutyric acid (GABA)-ergic input to the lateral (external) pallidal segment c) Glutamatergic input to the medial (internal) pallidal segment d) Dopaminergic inputs to the neostriatum e) Cholinergic inputs to the neostriatum 4. Which of the following pharmacological treatment strategies would be most appropriate for this patient? a) Cholinergic (muscarinic) agonist (Pilocarpine) b) Gamma aminobutyric acid (GABA)A agonist (Muscimol) c) L-3, 4-hydroxyphenylalanine (L-DOPA) plus a dopamine-decarboxylase inhibitor (Sinemet) d) Serotonin reuptake inhibitor (Prozac) e) Gamma aminobutyric acid (GABA)B agonist (Baclofen)

3. d) Dopaminergic inputs to the neostriatum 4. c) L-3, 4-hydroxyphenylalanine (L-DOPA) plus a dopamine-decarboxylase inhibitor (Sinemet) The patient described for these questions has Parkinson's disease. It is a hypokinetic disorder characterized by a reduction in spontaneous movements and facial expression, tremor (4 to 7 Hz), pill-rolling tremor, and monotonous speech. This disease results from a reduction or loss of dopaminergic input to the neostriatum from the pars compacta of the substantia nigra. One pharmacological approach used for the treatment of Parkinson's disease has been to administer Sinemet, which consists of a mixture of L-3, 4-hydroxyphenylalanine (L-DOPA), the precursor of dopamine, coupled with a dopa- mine-decarboxylase inhibitor. This drug serves as a means of providing dopamine to brain regions, such as the neostriatum, in place of the dopamine that would normally be provided from the pars compacta of the substantia nigra to the neostriatum

An individual is diagnosed with a cerebellar tumor. As a result, the patient presents with nausea, vomiting, dizziness, nystagmus, and wide "ataxic" gait with disturbances of equilibrium. 3) The tumor is most likely located in the: a. Dentate nucleus b. Interposed nuclei c. Lateral aspect of neocerebellar hemispheres d. Anterior lobe e. Flocculonodular lobe 4) A primary source of input to the region where the tumor is located includes: a. Dentate nucleus b. Red nucleus c. Cerebral cortex d. Vestibular nuclei e. Ventral horn of spinal cord

3. e. Flocculonodular lobe 4. d. Anterior lobe The flocculonodular lobe receives inputs from the vestibular system. Disruption of these inputs and the loss of ability to integrate such messages and provide the necessary feedback signals to the vestibular nuclei and reticular formation through the fastigial nuclei result in disturbances of gait and equilibrium as well as nystagmus. The cerebellar hemispheres are primarily concerned with movements associated with the distal musculature, as are the interposed and dentate nuclei, which are linked anatomically and functionally to the red nucleus and cerebral cortex. Axons of the ventral horn of the spinal cord project to skeletal muscle and not to the brainstem or cerebellum.

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A patient presents with double vision, drooping of the eyelid (ptosis), dilation of the pupil, a downward abducted eye, and inability to accommodate to a near object. A staff neurologist concluded that the patient had suffered damage to: a) Cranial nerve III b) Cranial nerve IV c) Cranial nerve VI d) Superior colliculus e) Lateral tegmentum

a) Cranial nerve III The somatomotor components of the oculomotor nerve (cranial nerve [CN] III) innervate the superior, inferior, and medial rectus muscles as well as the levator palpebrae and inferior oblique muscles. The parasympathetic components innervate the ciliary and papillary constrictor muscles. Therefore, damage to this nerve will cause lateral and downward deviation of the eye, because of the unopposed actions of the superior oblique and lateral rectus muscles, and will cause diplopia, because the effect is on one eye, thus preventing both eyes from working together. The drooping of the eye is the result of loss of innervation of the levator palpebrae muscle, dilation of the pupil is the result of parasympathetic loss to the pupillary constrictor muscles, and loss of accommodation occurred because of the combined loss of innervation to the medial rectus and ciliary muscles. CN IV and VI have no parasympathetic components; CN III passes ventrally to exit the brain through the floor of the midbrain, and, thus, lesions of either the superior colliculus or lateral tegmentum would not affect basic functions of CN III.

A patient visiting a neurologist complained of spells of dizziness while standing, dry mouth, constipation, and muscle weakness. A routine chest x-ray revealed a tumor in the lung. Biopsy of the tissue suggested the presence of small-cell carcinoma of the lung. The patient was diagnosed to be suffering from Lambert-Eaton syndrome. Which one of the following is likely to account for muscle weakness in this patient? a) Loss of voltage-gated calcium channels in the presynaptic terminals b) Loss of voltage-gated potassium channels in the neuronal cell body c) Excessive release of ACh from nerve terminals d) Blockade of voltage-gated sodium channels in the neurons e) Excessive increase in the conductance of chloride channels in the spinal motor neurons

a) Loss of voltage-gated calcium channels in the presynaptic terminals The patient is suffering from Lambert-Eaton syndrome. In patients with this syndrome, a specific antibody causes loss of voltage-gated calcium channels in the presynaptic terminal at the neuromuscular junction. Therefore, depolarization of the terminal does not open a sufficient number of calcium channels, and the release of the transmitter (ACh) is reduced. This results in muscle weakness. The patient's other symptoms are caused by the loss of voltage-gated calcium channels in the presynaptic terminals of the sympathetic and parasympathetic divisions of the autonomic nervous system.

A 69yo woman admitted to a local hospital after she reported that she couldn't move her legs. Neurologic examination indicated that not only did she lose motor functions in both of her legs but that she could not detect any sensation in either leg when probed with a safety pin. However, she was aware of sensation in both legs when the neurologist applied tactlle stimulation to them. IT was concluded that the patient suffered damage to the: a) anterior half of both sides of the spinal cord at the lumbar level b) posterior half of both sides of the spinal cord at the lumbar level c) region surrounding the central canal of the lumbar cord d) left half of the cervical cord e) dorsal roots of the lower thoracic cord, bilaterally

a) anterior half of both sides of the spinal cord at the lumbar level This is an example of an individual who suffered an occlusion of the anterior spinal artery, affecting the ventral half of the spinal cord. Such an occlusion would affect the ventral horns on both sides, causing paralysis of both legs. Damage to the ventral half of the spinal cord would also affect the spinothalamic tracts, resulting in the loss of pain impulses below the lesion bilaterally. Damage to the posterior half of the spinal cord would affect conscious proprioception but would not affect transmission of pain and temperature. Damage to the region of the central canal would only produce segmental loss of pain and temperature but would have no motor effects. Damage to the left half of the cervical cord would produce Brown-Séquard syndrome. Dorsal root ganglion damage would only produce sensory loss but would not cause limb paralysis.

A 45 yo man complained about having recurring headaches over a period of weeks. Subsequent tests revealed the presence of a tumor along the lateral wall of the anterior horn of the lateral ventricle, which did not produce hydrocephalus. One region that would be directly affected by the tumor is the: a) caudate nucleus b) putamen c) globus pallidus d) hippocampus e) cingulate gyrus

a) caudate nucleus The head of the caudate nucleus is located adjacent to the lateral aspect of the anterior horn of the lateral ventricle. Therefore, a tumor in this region would include the head of the caudate nucleus. The putamen and globus pallidus lie lateral to the caudate nucleus at a position away from the lateral ventricle, the hippocampus lies adjacent to the inferior horn of the lateral ventricle, and the cingulate gyrus lies above the corpus callosum in a position not in proximity to the lateral ventricle

An adult male suffering from chills, fever, headache, nausea, vomiting, and pain in the back was admitted to the ED and diagnosed as having meningococcal meningitis. Which of the following changes are most likely in the composition of the cerebrospinal fluid of this patient? a) increased protein, decreased glucose, and increased PMNs b) increased protein, normal glucose, and excessive number of lymphocytes c) increased protein, normal glucose, and a few WBCs d) increased protein, normal glucose, and presence of tumor cells and WBCs e) increased protein, increased glucose, and a few WBCs

a) increased protein, decreased glucose, and increased PMNs Increased protein, decreased glucose, and increased PMNs are observed in the CSF of patients with bacterial meningitis. The glucose levels in CSF decrease because the bacteria present in the CSF (usually, meningococcus, pneumococcus, and Haemophilus influenzae organisms) use glucose. The CSF glucose levels are low in tubercular meningitis also; however, in this condition, the cells in CSF are predominantly lymphocytes. In viral meningitis, the glucose levels in CSF remain normal because, in this condition, the viruses do not use glucose. In addition, the number of lymphocytes present in the CSF is excessive

Which one of the following arteries supplies the tegmentum of rostral and caudal pons and lateral midbrain? a. Paramedian branches of the basilar artery b. Long circumferential branches of basilar artery c. Superior cerebellar artery d. Calcarine artery e. Posterior spinal artery

b. Long circumferential branches of basilar artery The long circumferential arteries arise from the basilar supply in the pons and supply most of the tegmentum of the rostral and caudal pons and lateral portions of the midbrain tegmentum.

A 75yo man was admitted to the ED complaining that he had trouble walking and that he could not move his arms as well. An MRI revealed the presence of a brain tumor. Tracer dye injected into the lateral ventricle did not appear in the lumbar CSF, suggesting that the patient had developed a noncommunicating hydrocephalus. Which one of the following is the most likely location of the tumor? a) interventricular foramen b) cerebellar cortex c) cerebral cortex d) lateral thalamus e) lateral medullary reticular formation

a) interventricular foramen In patients suffering from hydrocephalus, the circulation of CSF is blocked or its absorption is impeded, while the CSF formation continues to occur. The ventricles dilate, and pressure is exerted on the adjacent tissue, causing impairment of such structures as the corticobulbar and corticospinal tracts. Therefore, a progressive loss of motor function ensues. Hydrocephalus that develops when the movement of CSF out of the ventricular system is impeded is called noncommunicating hydrocephalus. In noncommunicating hydrocephalus, a tracer dye injected into the lateral ventricle does not appear in the lumbar CSF, indicating that there is an obstruction to the flow of CSF in the ventricular pathways. Therefore, of the structures listed as choices, the interventricular foramen is the most likely site where the tumor is present. IF the movement of the CSF into the dural venous sinuses is impeded or blocked by an obstruction at the arachnoid villi, this type of hydrocephalus is called a communicating hydrocephalus. A tracer dye injected into the lateral ventricle in this condition does appear in the lumbar CSF, indicating that there is no obstruction to the flow of CSSF in the ventricular or extraventricular pathways.

Examination of a patient reveals the presence of a right lateral gaze palsy and diplopia as well as a loss of ability to express a smile on the right side of the face. The primary focus of the lesion is on: a) the dorsal aspect of the right caudal pons b) the dorsal aspect of the right rostral pons c) the caudal aspect of the basilar pons on the left side d) the caudal aspect of the basilar pons on the right side e) the midline on the pons at the level of the main sensory nucleus of cranial nerve V

a) the dorsal aspect of the right caudal pons The loss of ability for the right eye to gaze laterally coupled with loss of control over the muscles of facial expression can be only occur if the lesion is present in the region of the facial colliculus, which includes the fibers of cranial nerve (CN) VII passing over the nucleus of CN VI. Lesions in the other regions would not include both of these cranial nerve structures.

There is a convergence of inputs from the dorsal spinocerebellar, ventral spinocerebellar, and cuneocerebellar tracts within the cerebellum. These major cerebellar afferent fibers terminate primarily in the: a. Anterior lobe b. Posterior lobe c. Flocculonodular lobe d. Interposed nuclei e. Dentate nucleus

a. Anterior lobe The anterior lobe receives major inputs from the spinal cord and is referred to as the "spinocerebellum." These inputs contain fibers that convey signals associated with muscle spindle and Golgi tendon activity as well as some tactile inputs that are transmitted through the dorsal spinocerebellar, ventral spinocerebellar, and cuneocerebellar tracts. The posterior lobe receives inputs mainly from the cerebral cortex, inferior olivary nucleus, red nucleus, and reticular formation. The flocculonodular lobe receives inputs from vestibular neurons. The dentate and interposed nuclei are anatomically and functionally related mainly to the posterior lobe and, in addition, receive only collateral inputs from fibers that are afferent to the cerebellum.

A middle-aged man was admitted to a local hospital with a cerebellar hemorrhage resulting from hypertension. Several days later, the patient displayed "past pointing" and "asynergia of movement." The region of cerebellum that was most likely affected by the hemorrhage was: a. Fastigial nucleus b. Neocerebellar hemispheres c. Vermal region of the anterior lobe d. Vermal region of the posterior lobe e. Flocculonodular lobe

b. Neocerebellar hemispheres A variety of the cerebellar ataxias are associated with lesions of the neocerebellar hemispheres, in particular, if the movement disorders involve the distal musculature. "Past pointing" involves the distal musculature, and asynergia of movement is associated with a failure of the planning mode of the cerebellar cortex, which is represented in the neocerebellar hemispheres. The axial musculature is represented in the vermal region.

A 68-year-old man fell down a flight of stairs. Although the patient was not seriously injured from the fall, he reported that he experienced double vision when he attempted to walk down the stairs. Neurologic examination failed to show any other evidence of diplopia when the patient was asked to move his eyes upward or to either side. The neurologist concluded that there was damage to: a) Cranial nerve III b) Cranial nerve IV c) Cranial nerve VI d) Ventromedial aspect of midbrain e) Superior colliculus

b) Cranial nerve IV The trochlear nerve (cranial nerve [CN] IV) innervates the superior oblique muscle, whose action brings the eye downward. Damage to this nerve produces diplopia, which is most pronounced when attempting to look downward, such as when attempting to walk down a flight of stairs. The other choices are clearly incorrect. Damage to CN III and VI would produce a different constellation of deficits, most notably effects upon medial and lateral gaze, respectively. Since CN IV exits the brainstem dorsally at the pontine midbrain border, lesions of the ventromedial midbrain or superior colliculus would not affect the functions of this nerve

A 50yo complained to his neurologist that he was suffering from a generalized muscle weakness that was exacerbated when he exercised. The patient's history revealed that he suffered from a viral infection 4 to 5 weeks prior to the onset of muscle weakness. The neurologist suspected that the patient was suffering from myasthenia gravis and prescribed drug treatment with neostigmine. Following this treatment, the patient reported a significant improvement in his symptoms. Which one of the following could have accounted for muscle weakness in this patient? a) Reduction of voltage-gated calcium channels on the presynaptic terminals b) Reduction in the number of functional nicotinic ACh receptors on the muscle end-plates c) Reduction in the release of ACh at the muscle end-plates d) Demyelination of nerves innervating the muscle end-plates e) Demyelination of axons in the CNS

b) Reduction in the number of functional nicotinic ACh receptors on the muscle end-plates The patient is suffering from myasthenia gravis. The virus that had infected the patient 4 to 5 weeks prior to the onset of the muscle weakness may have contained an amino acid sequence similar to that present in the nicotinic ACh receptor (nAChR). The patient's T cells may have become reactive and produced an antibody against the nAChR. The circulating antibody may have bound to the nAChRs on the muscle end-plates, thus, reducing the number of functional nAChRs. Consequently, ACh released from the presynaptic terminals did not activate a sufficient number of nAChRs at the neuromuscular junction, thus producing muscle weakness. Neostigmine, an acetylcholinesterase inhibitor, may have increased the probability of interaction of the neurotransmitter with the remaining functional nAChRs by reducing the destruction of released ACh. Therefore, the patient's muscle weakness was reversed in myasthenia gravis, there is no defect in myelination of axons either in the CNS or PNS. Reduction in the number of functional voltage-gated calcium channels does not occur in myasthenia gravis; it is a characteristic of Lambert-Eaton Syndrome.

A 61yo man complained to his local physician that his legs had begun to feel weak over the past few months and that the weakness was progressive over time. Some time following the initial examination, the patient was unable to move his legs and, several months later, his arms began to show weakness as well. Eventually, he couldn't move his limbs at all, and, in addition, he began to lose bladder control. Sensation seemed to be relatively intact. A comprehensive neurologic examination led the neurologist to conclude that the patient was suffering from: a) syringomelia b) amyotrophic lateral sclerosis c) multiple sclerosis d) combined systems disease e) tabes dorsalis

b) amyotrophic lateral sclerosis Progressive loss of motor functions, starting with the lower limbs and extending to the upper limbs, is characteristic of amyotrophic lateral sclerosis, which results in the destruction of ventral horn cells and, eventually, descending motor pathways. There is little or no sensory loss. In contrast, the other choices produce disorders that include components of sensory loss.

Which of the following statements is correct concerning chemical transmission at a synapse? a) continuity of the cytoplasm between the presynaptic and postsynaptic neurons is necessary b) calcium entry into the presynaptic terminal is an important step in this type of transmission c) the nature of the response elicited depends upon the chemical nature of the transmitter d) it involves transmitter release by endocytosis e) this type of transmission is uncommon in the CNS

b) calcium entry into the presynaptic terminal is an important step in this type of transmission At the chemical synapse, there is no continuity between the cytoplasm of the presynaptic and postsynaptic cell. Instead, the cells are separated by fluid-filled gaps that are relatively large (about 20-50nm). Calcium entry into the presynaptic nerve terminal is necessary for the release of the transmitter. The neurotransmitter then interacts with its specific receptors and opens or closes several thousand channels in the postsynaptic membrane. The nature of the response (i.e. excitatory or inhibitory) elicited at the postsynaptic neuron does not depend on the chemical nature of the transmitter. Instead, it depends on the type of receptor being activated. Instead, it depends on the type of receptor being activated and the ion species that becomes more permeable. Transmitter release involves a process called exocytosis, in which the vesicles containing the transmitter fuse with the presynaptic membrane and release their contents into the synaptic cell. Neurotransmission in the nervous system involves predominantly chemical synapses.

An elderly female patient was diagnosed as having had a stroke, which caused loss of pain to the left side of her face and head and to the right side of her body and flushing of the left side of her face. Where was the locus of this lesion? a) ventromedial aspect of right caudal medulla b) dorsolateral aspect of left rostral medulla c) dorsomedial aspect of right caudal medulla d) midline region of medulla-spinal cord border e) dorsomedial aspect of the medulla-pons border

b) dorsolateral aspect of left rostral medulla A lesion of the dorsolateral aspect of the left medulla would affect first-order pain fibers (and second-order neuronal cell bodies of the trigeminal complex) associated with the left side of the face. Pain fibers associated with the body have already crossed in the spinal cord. Thus, this lesion would affect pain sensation from the right side of the body. The flushing of the face would result from the loss of descending autonomic fibers from the hypothalamus, which controls the sympathetic nervous system, thus producing a flushing of the face known as Horner's syndrome. The medial aspect of the medulla does not contain pain fibers from either the head or body.

Which of the following statements is correct concerning a gap junction? a) The neurons at a gap junction are separated by a large (20-50 nm) space b) gap junction channels are formed by two hemichannels connecting presynaptic and postsynaptic neurons c) these channels are transmitter gated d) at the gap junction, the current generated by an impulse in one neuron spreads to another neuron through a pathway of high resistance e) usually, gap junctions allow flow of current in only one direction

b) gap junction channels are formed by two hemichannels connecting presynaptic and postsynaptic neurons In electrical transmission between the nerve cells, the current generated by an impulse in one neuron spreads to another neuron through a pathway of low resistance (these channels are not transmitter gated). Such a pathway has been identified at gap junctions. The area where the two neurons are apposed to each other, at an electrical synapse, is called a gap junction. The extracellular space between presynaptic and postsynaptic neurons at an electrical synapse is 3 to 3.5 nm, which is much smaller than the usual extracellular space (about 20-50 nm) between neurons. These channels are formed by two hemichannels, one in the presynaptic and the other in the postsynaptic neuron. Most gap junctions allow ion flow in both directions.

Which one of the following arteries supplies the tegmentum of rostral and caudal pons and lateral midbrain? a. Paramedian branches of the basilar artery b. Long circumferential branches of basilar artery c. Superior cerebellar artery d. Calcarine artery e. Posterior spinal artery

b. Long circumferential branches of basilar artery

A 50yo man was admitted to the emergency room after a head injury resulting from an automobile accidente. The patient was diagnosed as having a subarachnoid hemorrhage. Which of the following changes are most likely in the composition of the CSF of this patient? a) decreased protein, normal glucose, and presence of a few WBCs b) increased protein, normal glucose, and presence of RBCs c) increased protein, decreased glucose, and presence of PMNs d) decreased protein, normal glucose, and presence of a small number of lymphocytes e) decreased protein, decreased glucose, and presence of tumor cells

b) increased protein, normal glucose, and presence of RBCs Normal CSF may contain a few lymphocytes and PMNs, but it contains no RBCs. The presence of RBCs in CSF is characteristic of subarachnoid hemorrhage. In viral and tubercular meningitis and metastatic cancer, the CSF will show an increased number of lymphocytes, wehereas the number of PMNs is increased in bacterial meningitis. Most pathologic conditions do not decrease protein levels in the CSF; glucose level may be decreased in metastatic cancer and tubercular or bacterial meningitis. The presence of WBCs in the CSF occurs in pathologies other than subarachnoid hemorrhage

Which of the following statements is correct regarding the voltage-gated sodium channel? a) it is in an open state at the resting membrane potential b) it is blocked by local anesthetic drugs c) it is formed by several long polypeptide chains d) it is equally permeable to Na+ as well as K+ ions e) it can be activated during the falling phase of the action potential

b) it is blocked by local anesthetic drugs The channel is formed by a single long polypeptide that has four domains (I-IV). Each domain has six hydrophobic alpha helices (S1-S6) that span back and forth within the cell membrane. The four domains joins together and form an aqueous pore of the channel. These channels open during the rising phase of the action potential. At the resting membrane potential, the channel pore is closed. When the neuron is depolarized, the channel gate opens, allowing an influx of sodium ions. They are blocked by a poison, called TTX, obtained from the puffer fish, and local anesthetic drugs (e.g. lidocaine). At the end of the rising phase of the action potential, the voltage-gated Na+ channels are inactivated. They cannot be activated to generate an action potential until the membrane potential becomes adequately negative and the Na+ channels get de-inactivated. The period during which the Na+ channels are in an inactivated state and an action potential cannot be generated is called the absolute refractory period.

Which of the following statements is correct regarding a graded potential? a) it has a threshold b) its amplitude varies with the intensity of the stimulus c) it has a long refractory period d) it has a constant duration e) it is mediated via a voltage-gated ion channel

b) its amplitude varies with the intensity of the stimulus The amplitude of a graded potential varies with the intensity of the stimulus; the response is graded. It has no threshold or refractory period. Its duration depends on the initial stimulus. It is mediated by a receptor (not voltage-gated ion channel).

Conscious proprioception from the upper limbs to the thalamus is mediated through the: a) nucleus gracilis b) nucleus cuneatus c) spinal trigeminal nucleus d) inferior olivary nucleus e) nuclei of reticular formation of rostral medulla

b) nucleus cuneatus First-order neurons mediating conscious proprioception from the body pass from the periphery through the dorsal columns of the spinal cord to the dorsal column nuclei of the lower medulla, where they terminate. Fibers associated with this type of sensation from the upper limbs terminate upon the nucleus cuneatus, whereas fibers associated with the lower limb terminate upon the nucleus gracilis. These nuclei thens project their axons to the contralateral thalamus.

A 79yo woman is admitted to the ED after she was found unconscious in her apartment. After she regained consciousness, a neurologic examination indicated that she suffered a stroke with paralysis of the right arm and leg as well as loss of speech. The most likely region affected by the stroke that could account for limb paralysis is: a) prefrontal cortex b) precentral gyrus c) postcentral gyrus d) superior temporal gyrus e) parietal lobe

b) precentral gyrus The primary motor cortex is located in the precentral gyrus, which is organized somatotopically. The functions of the upper and lower limbs are represented in different regions along the precentral gyrus. The postcentral gyrus represents a primary somesthetic receiving area for pain, temperature, pressure, kinesthetic, and tactile impulses from the periphery. Although the superior frontal gyrus contains certain groups of neurons (the supplementary and premotor motor areas) that also contribute to motor functions, it is not a primary motor area. The superior parietal lobule is associated with sensory discrimination processes and with the programming of signals to the premotor cortex. The posterior parietal cortex represents a region of sensorimotor integration and the organization of complex response patterns.

Which one of the following arteries supplies the medial structures of the medulla, including the pyramids, medial lemniscus, medial longitudinal fasciculus, hypoglossal nucleus, and inferior olivary nucleus? a. Posterior spinal artery b. Anterior spinal artery c. Lenticulostriate branches of the middle cerebral artery d. Medial striate artery e. Callosomarginal artery

b. Anterior spinal artery Two small arteries arise at the confluence of the two vertebral arteries which join to form a single anterior spinal artery. This artery supplies the medial structures of the medulla, which include the pyramids, medial lemniscus, medial longitudinal fasciculus, hypoglossal nucleus, and the inferior olivary nucleus. The axons contained within the pyramid originate in the cerebral cortex. At the juncture of the medulla with the spinal cord, most of the fibers contained within the pyramid pass to the contralateral side through a commissure, the pyramidal decussation.

A patient exhibits a variety of behavioral and language problems such as a failure to inhibit responses that are socially inappropriate. Such an individual is most likely to suffer from dementia involving the: a. Parieto-occipital region b. Frontal cortex c. Inferior temporal cortex d. Corpus callosum e. Caudate nucleus

b. Frontal cortex The frontal cortex, particularly the prefrontal region, plays an important role in cognitive functions and in the regulation of emotional behavior. Parts of the frontal lobe (i.e., Broca's area) and superior aspect of the temporal lobe (Wernicke's area) mediate the motor and receptive components of speech. Neither the parieto-occipital region nor inferior temporal cortex is directly involved in these functions. The corpus callosum mediates the transmission of information from one side of the cortex to the other, and the caudate nucleus is associated with the cognitive aspects of motor functions.

A 72-year-old man was found unconscious in his home and was taken to the emergency room of the local hospital. After a few days, the patient remained in a coma, and the pattern on his electroencephalogram revealed mainly the presence of an alpha-like rhythm. In addition, the patient presented with normal eye movements and a variety of autonomic and somatomotor reflexes. On the basis of these observations as well as a magnetic resonance imaging scan, the neurologist concluded that the lesion was localized to the: a. Medulla b. Pons c. Midbrain d. Diencephalon e. Cerebral cortex

b. Pons The disorder described in this case is referred to as "coma vigil." It is characteristic of a pontine lesion, which includes parts of the tegmentum but spares the dorsomedial region, which is associated with the control of horizontal eye movements. Although the patient is comatose, his electroencephalographic response is characteristic of an alpha rhythm, and horizontal eye movements are clearly present. Lesions of that medulla usually are fatal; lesions involving the other choices do not produce the symptoms described in this case, such as the alpha-like rhythms and eye movements.

Rapid eye movement (REM) sleep is believed to originate in the: a. Caudal medulla b. Pons c. Midbrain d. Lateral hypothalamus e. Medial thalamus

b. Pons Electrophysiological studies have indicated that rapid eye movement (REM) sleep originates in the pontine reticular formation. Activation of this pathway modulates cortical activity in association with REM sleep. Other choices include regions that have never been associated with induction of REM sleep. The caudal medulla contains few reticular formation neurons, and the general region of the caudal medulla contains cell bodies and axons associated with transmission of sensory information to higher regions, cranial nerve function, and descending fibers to the spinal cord. The midbrain contains neurons comprising part of the reticular formation but lacks the cholinergic cell groups essential for generation of REM sleep, which is characteristic of those present in the pontine reticular formation. The lateral hypothalamus is associated with visceral processes, such as feeding, and contains ascending and descending fibers associated with limbic structures and monoaminergic systems that are unrelated to REM sleep. The medial thalamus is concerned with the transmission of impulses mainly to the frontal lobe and has no known relationship to REM sleep.

A patient presented with paralysis of the left side of the limbs and left side of the lower face and deviation of the tongue to the left with no atrophy and with no loss of taste sensation. This constellation of deficits most likely resulted from a lesion of the: a. Left internal capsule b. Right internal capsule c. Left pontine tegmentum d. Ventromedial medulla on the right side e. Ventromedial medulla on the left side

b. Right internal capsule The right internal capsule contains corticospinal and corticobulbar fibers that project to the contralateral spinal cord and to the brainstem. The corticobulbar fibers that project predominantly to the contralateral side include those fibers that innervate motor nuclei of cranial nerves VII (lower facial muscles) and XII (hypoglossal). Therefore, a lesion of the right internal capsule will result in paralysis of the limbs on the left side, a deviation of the tongue to the left side (i.e., side opposite to the lesion), and paralysis of the right side of the lower face. A lesion of the right ventromedial medulla is too far caudal to affect corticobulbar fibers that supply the facial nucleus. Be- cause the defects are on the left side, all of the choices that involve a lesion on the same (i.e., left) side are incorrect because lesions of the corticospinal and corticobulbar fibers result in motor deficits that are manifested on the contralateral side.

midbrain

brain region: brainstem general functions: transmission and regulation of sensory, motor, and autonomic functions (cranial nerves III and IV) associated disorder(s): sensory, motor, and autonomic deficits as well as deficits associated with cranial nerves III and IV

pons

brain region: brainstem general functions: transmission and regulation of sensory, motor, and autonomic functions (cranial nerves V, VI, VII, and VIII) associated disorder(s): sensory, motor, and autonomic deficits as well as deficits associated with cranial nerves V, VI, and VII

medulla

brain region: brainstem general functions: transmission and regulation of sensory, motor, and autonomic functions (cranial nerves, V, VIII, IX, X, XII) associated disorder(s): sensory, motor, and autonomic deficits, including respiration, as well as deficits associated with cranial nerves VIII, IX, X, and XII

cerebellum: anterior, posterior, and flocculonodular lobes

brain region: cerebellum general functions: integration of motor functions related to all regions of the CNS associated with motor and related processes associated disorder(s): loss of balance; ataxia; hypotonia; loss of coordination; disorders of movement when intentionally attempting to produce a purposeful response

A 55-year-old man was recently diagnosed with Huntington's disease. This disorder may best be understood in terms of the loss of which substance with which result? a) Serotonin in the globus pallidus, increased excitation of ventral anterior thalamic nucleus b) Substance P in the neostriatum, increased inhibition in the medial pallidal segment c) Gamma aminobutyric acid (GABA) in the neostriatum, reduction of neostriatal inhibition on the lateral (external) pallidal segment d) Acetylcholine and gamma aminobutyric acid (GABA) in the neostriatum, reduction of inhibition on the medial (internal) pallidal segment e) Dopamine in the neostriatum, a reduction of neostriatal

c) Gamma aminobutyric acid (GABA) in the neostriatum, reduction of neostriatal inhibition on the lateral (external) pallidal segment The lateral segment of the globus pallidus projects gamma aminobutyric acid (GABA)-ergic fibers to the subthalamic nucleus. This connection represents the first limb of the indirect pathway connecting the striatum, subthalamic nucleus, and thalamus. In turn, the subthalamic nucleus provides an excitatory, glutamatergic input to the medial pallidal segment; and the medial segment inhibits the ventrolateral and ventral anterior nuclei of thalamus (which normally excite motor regions of cortex) by virtue of its GABAergic projection. Thus, when the inhibitory GABAergic input to the lateral pallidal segment is lost, as is the case in Huntington's disease, the GABAergic input into the subthalamic nucleus from the lateral pallidal segment is more pronounced. Consequently, there is a weaker excitatory input into the medial pallidal segment from the subthalamic nucleus, resulting in less inhibition from the medial pallidal segment on the thalamic nucleus and motor regions of cortex. Hence, the loss of neostriatal GABA is manifested in the form of a hyperkinetic effect on motor responses. The other choices are incorrect for the following reasons. The role of serotonin in the globus pallidus is unknown and, therefore, not likely to play any significant role in this structure related to a hyperkinetic disorder. Substance P is excitatory and, therefore, could not be related to inhibitory processes. Acetylcholine is an excitatory transmitter, loss of which would not produce a reduction in inhibition. Loss of dopamine in the neostriatum is associated with a hypokinetic rather than a hyperkinetic disorder.

The corpus callosum of each of 20 patients was severed in order to reduce the spread of seizure activity. The patients were then asked to participate in a research study to identify specific features of brain function. The most likely purpose of this study was to: a) Identify the different areas of the cortex that mediate speech functions b) Identify how the corpus callosum mediates visual functions c) Identify the various properties of cerebral dominance d) Identify the cortical sites mediating movement of the fingers e) Characterize thalamocortical relationships

c) Identify the various properties of cerebral dominance Much of the knowledge we have recently obtained concerning cerebral dominance has come from studies of patients whose corpus callosum has been cut in order to reduce the spread of seizure activity. These patients have been ideal subjects for determining which side of the cerebral cortex is dominant with respect to a variety of functions such as music, language, mathematics, and spatial perception. The corpus callosum plays a minimal role in transferring visual information and information concerning movements of the fingers. Removal of the corpus callosum is not necessary to characterize the different areas of the cortex that mediate speech functions. Also, sectioning of the corpus callosum would not serve any purpose in examining thalamocortical connections, which typically involve relationships on the same side of the brain.

Which of the following statements is correct regarding the rising phase of an action potential in a neuron? a) the membrane potential becomes more negative during this phase b) there is an influx of sodium through the nongated ion channels c) Na+ flows into the neuron through voltage-gated sodium channels d) K+ flows into the neuron through the voltage-gated K+ channels e) energy for influx of Na+ is provided by the Na+-K+ pump

c) Na+ flows into the neuron through voltage-gated sodium channels When the membrane depolarizes beyond the threshold potential, a sufficient number of voltage-gated Na+ channels opens, and there is an influx of Na+ during the rising phase of the AP. The membrane potential becomes less negative during depolarization. The flow of ions through the voltage-gated channels during the rising phase of the action potential does not require energy. At the end of the depolarization, there is an efflux of K+, and the neuron repolarizes

A 22yo man was admitted to the ED after a motorcycle accident. A clinical examination showed that he had elevated ICP due to head trauma. The patient suffered from severe bradycardia. Acting on which of the following brain regions would elevated ICP most likely cause bradycardia? a) cerebral cortex b) basal ganglia c) brainstem d) thalamus e) cerebellum

c) brainstem The craniovertebral cavity and its dural lining form a closed space. An increase in the size or volume of any constituent of the cranial cavity results in an increase in ICP. The following symptoms may accompany increased ICP: loss of consciousness, headache, nausea and vomiting, increase in systemic blood pressure, and bradycardia. The bradycardia (decrease in heart rate) is usually due to the increased pressure on the nucleus ambiguus and dorsal motor nucleus of vagus located in the medulla. The other brain structures listed are not involved in the control of heart rate.

A 56yo man was admitted to the ED after fainting in a hallway of his apartment building. Two days later, he was able to open his eyes and began to regain some basic functions. However, a neurologic examination revealed that he was not able to move his left arm or leg. In addition, he lost some sensation his left leg and arm, and when he tried to extend his tongue, it deviated to the right side. Where was the location of the lesion? a) at the border of the spinal cord and medulla b) in the dorsomedial medulla c) in the ventromedial medulla d) in the dorsolateral medulla e) at the border between medulla and pons

c) in the ventromedial medulla The fiber bundle mediating upper motor neuron control over movements of the contralateral arm and leg is the pyramids, which are situated in the ventromedial aspect of the medulla. Sensory impulses from the left limbs are mediated through the right brainstem medial lemniscus as a result of a decussation of this pathway at its site of origin. Lesions of the hypoglossal nerve result in deviation of the tongue to the side of the lesion due to the unopposed action of the contralateral hypoglossal nerve upon the tongue muscles when the tongue is protruded. All of these structures lie in the ventromedial aspect of the medulla. Thus, the other choices are incorrect because they do not contain all of these structures.

A 79yo woman is admitted to the ED after she was found unconscious in her apartment. After she regained consciousness, a neurologic examination indicated that she suffered a stroke with paralysis of the right arm and leg as well as loss of speech. The loss of speech in this patient was due mainly to damage of the: a) superior frontal cortex b) inferior temporal gyrus c) inferior frontal gyrus d) occipital cortex e) medial aspect of parietal cortex

c) inferior frontal gyrus The posterior aspect of the inferior frontal gyrus contains a region called "Broca's motor speech" area. LEsions affecting this region produce motor aphasia, which is characterized by a loss of ability to express thoughts in a meaningful manner. The superior aspect of the frontal cortex is associated with movements of the lower limbs, the inferior temporal gyrus is associated with perceptual functions, the occipital cortex is associated with vision, and the medial aspect of the parietal lobe is associated with somatosensory functions involving the leg.

A 47yo woman is admitted to the ED.She is diagnosed as having a vascular infarction of the brainstem, resulting in loss of conscious proprioception, pain, and temperature of both the same side of her body and face. The neurologist concluded that the affected region included the: a) midbrain periaqueductal gray b) tectal area c) lateral aspect of midbrain d) medial aspect of dorsal midbrain e) ventromedial aspect of midbrain

c) lateral aspect of midbrain The lateral aspect of the midbrain tegmentum contains the spinothalamic and trigeminothalamic tracts as well as the me- dial lemniscus. Thus, damage to the lateral tegmentum would cause loss of pain and temperature sensation to both the head and body and loss of conscious proprioception to the con- tralateral side of the body. The loss in each case would be contralateral to the side of the lesion because the pathways mediating these sensations have already crossed, either at the spinal cord (for spinothalamic fibers) or lower brainstem (for the medial lemniscus and trigeminothalamic fibers). The other regions do not contain any of these pathways.

hippocampal formation, amygdala, septal area, cingulate gyrus, prefrontal cortex

diencephalon brain region: limbic structures general functions: modulation of hypothalamic functions; regulation of emotional behavior; short-term memory associated disorder(s): temporal lobe epilepsy; loss of control of emotions and related affective processes; loss of short term memory

During a routine examination, a physician attempted to elicit a gag reflex response in a patient by stroking the posterior pharynx with a cotton-tipped probe. This reflex is initiated primarily by activating the sensory endings of: a. Cranial nerve V b. Cranial nerve VII c. Cranial nerve IX d. Cranial nerve XI e. Cranial nerve XII

c. Cranial nerve IX The afferent (sensory) limb of the gag reflex involves somatic afferent fibers (i.e., general somatic afferent) of the glossopharyngeal (cranial nerve [CN] IX) nerve that enter the brainstem and make a synapse with special visceral motor fibers of CN X, whose axons comprise the efferent (motor) limb of the reflex that innervates pharyngeal muscles. The other cranial nerves are not involved in this reflex.

A 67-year-old man was taken to the emergency room after collapsing in a movie theater. The patient regained consciousness and, several days later, displayed a right-side paralysis with pronounced spasticity. The neurologist concluded that the stroke might have involved: a. Ventral horn cells b. Cerebellum c. Internal capsule d. Postcentral gyrus e. Pontine tegmentum

c. Internal capsule An upper motor neuron paralysis results in a paralysis or paresis of the contralateral limb(s), Babinski sign, spasticity, and hypertonicity. The most common sites where lesions produce this syndrome include the motor regions of the cerebral cortex, internal capsule, and other regions that contain the descending fibers of the corticospinal and corticobulbar tracts, such as the basilar pons and lateral funiculus of the spinal cord. A lower motor neuron paralysis is characterized by a flaccid paralysis of the affected limbs and results from a lesion of the ventral horn cells that innervate the muscles in question directly. Regions such as the cerebellum, postcentral gyrus, and pontine tegmentum do not produce paralysis and spasticity when damaged. They do produce other deficits, such as movement disorders with respect to the cerebellum, coma with respect to the pontine tegmentum, and somatosensory deficits with respect to the postcentral gyrus, which are described in later chapters.

Which one of the following arteries supplies the anteromedial part of the head of caudate nucleus and parts of the internal capsule, putamen, and septal nuclei? a. Anterior communicating artery b. Middle cerebral artery c. Medial striate artery (recurrent artery of Heubner) d. Anterior inferior cerebellar artery e. Posterior inferior cerebellar artery

c. Medial striate artery (recurrent artery of Heubner) The medial striate artery (recurrent artery of Heubner) arises from the anterior cerebral artery at the level of the optic chiasm and supplies blood to the anteromedial part of the head and caudate nucleus

A middle-aged, male professor of neuroscience at a north- eastern medical school began to experience intermittent episodes of uncontrollable sleep, even while giving lectures to the first-year medical class. At the request of colleagues and students, it was suggested that he see a neurologist in the university hospital. The neurologic examination revealed temporary loss of muscle tone in the trunk and extremities, and in the sleep clinic, he experienced some hallucinations and tended to remain awake at night. The neurologist concluded that the patient was suffering from: a. A brainstem stroke b. A cortical stroke c. Narcolepsy d. Depression e. Sleep apnea

c. Narcolepsy The constellation of symptoms described in this case is characteristic of narcolepsy. In narcolepsy, the patient has frequent bouts of sleep during the day, an inability to sleep at night, and loss of muscle tone. Sleep apnea is characterized by an interruption of breathing during sleep, with considerable snoring. A cortical or brainstem stroke would significantly disable the patient, and the symptoms associated with these lesions are totally distinct from those described in this case and would likely involve paralysis and, perhaps, coma. Although depression commonly is associated with problems in sleeping, it does not involve either loss of muscle tone or frequent bouts of sleep during the day as described in this case.

A 34-year-old man is hit in the head with a heavy object that was carelessly thrown out of a window under which he was walking. He was taken to the emergency room, given a magnetic resonance imaging (MRI) scan, and 36 hours later, regained consciousness. Several days later, the patient reported difficulty in following a moving object presented within his visual field and also felt little or no sensation of the forehead after a mild pinprick administered to that region. The MRI provided evidence that the head injury most likely caused damage to: a. Peripheral fibers of the facial nerve b. Central processes of the trigeminal nerve c. Nerve fibers in the superior orbital fissure d. The ventral half of the midbrain e. Processes passing through the jugular foramen

c. Nerve fibers in the superior orbital fissure Cranial nerves (CN) III, IV, and VI exit the skull through the superior orbital fissure. The ophthalmic division of the trigeminal nerve (CN V) also exits through the superior orbital fissure. Therefore, any damage to this fissure would affect functions of these cranial nerves. In this case, there would be loss of ability to move the eyes, such as in following a moving object, and there would also be loss of pain and temperature sensation to the forehead because of damage to the ophthalmic division of the trigeminal nerve. The other choices cannot account for this constellation of deficits (i.e., the facial nerve is not involved in this disorder; central processes of the trigeminal nerve could only account for the sensory losses; damage to the ventral midbrain would affect CN III but not CN VI, IV, and V; and the jugular foramen does not contain any of these cranial nerves).

A 35-year-old man suffered a stroke that did not cause paralysis. However, he discovered that he was unable to perform complex learned movements. The region of the cerebral cortex most likely affected by the stroke was the: a. Precentral gyrus b. Postcentral gyrus c. Premotor cortex d. Temporal neocortex e. Prefrontal cortex

c. Premotor cortex The premotor area is extremely important in providing sequencing or programming mechanism for learned movements. The most significant inputs come from the posterior parietal cortex. The premotor cortex then signals the appropriate groups of neurons in the spinal cord (and/or brainstem) to respond in a particular set of sequences. Therefore, damage to this region would result in loss of the sequencing mechanism that is so necessary for the occurrence of complex learned movements. The resulting disorder is called apraxia. Damage to the postcentral gyrus will produce a somatosensory loss. Damage to the precentral gyrus will produce an upper motor neuron paralysis. Damage to the temporal cortex will produce an auditory loss, and damage to the prefrontal cortex will produce different kinds of intellectual deficits, none of which include apraxia.

thalamic nuclei

diencephalon brain region: thalamus general functions: transmission of signals from other regions of the CNS to the cerebral cortex mediating sensory, motor, cognitive, and affective (emotional) functions associated disorder(s): disruption, loss, or alterations in visceral and affective functions and processes

An investigator designed an experiment to characterize how neurons in the lower brainstem respond to administration of a specific neurotoxic substance. To effectively carry out this study, it was necessary to use a decerebrate preparation in which the region of the brain rostral to the pons was disconnected from the brainstem and spinal cord. Following this surgery, the investigator noted that the animal displayed marked rigidity of the limbs, which was most pronounced in the hind limbs. When the student of this investigator asked why there was such pronounced rigidity, the investigator should have provided which of the following reasons? a. There is direct loss of inhibitory neurons from the motor cortex to the spinal cord. b. There is damage to the red nucleus with preservation of the reticulospinal tracts and cerebellar cortex. c. There is preservation of the lateral vestibulospinal tract with loss of cortical inputs to reticular formation. d. There is loss of hypothalamic inputs to the brainstem, which normally have excitatory effects on inhibitory pathways of the brainstem. e. There is selective loss of input from the cerebral cortex to the pontine reticular formation and medial reticulospinal tract.

c. There is preservation of the lateral vestibulospinal tract with loss of cortical inputs to reticular formation. The lateral vestibular nucleus gives rise to the lateral vestibulospinal tract, which projects to all levels of the spinal cord. The tract passes in the ventral funiculus of the cord and innervates alpha and gamma motor neurons of extensors and provides powerful excitation of these neurons. A decerebrate preparation leaves this pathway intact, while other inhibitory inputs are lost, in particular, to the reticular formation and its descending motor pathways. Collectively, this allows for un- opposed excitatory actions of the lateral vestibulospinal tract on extensor motor neurons. The other choices are incorrect. The influence of the motor cortex on the spinal cord is generally excitatory. The red nucleus excites flexor motor neurons, and its loss would not account for decerebrate rigidity. In addition, reticulospinal pathways (in particular, the lateral reticulospinal tract) are dependent on inputs from the cerebral cortex, and, thus, their effects on spinal motor neurons would not be preserved. The medial reticulospinal tract facilitates extensor motor tone. Accordingly, the rigidity could not be accounted for by postulating a selective loss of cortical inputs to this pathway because it would imply that such loss would achieve just the opposite of rigidity. The hypothalamus has no known influences on extensor motor tone.

premotor region

cerebral cortex brain region: frontal lobe general functions: aids and integrates voluntary movements of body associated disorder(s): apraxia (loss of ability to carry out complex movements of body and head)

frontal eye fields

cerebral cortex brain region: frontal lobe general functions: controls voluntary horizontal movements of the eyes associated disorder(s): loss of voluntary control of horizontal eye movement (i.e. eyes cannot deviate to side opposite lesion)

prefrontal cortex

cerebral cortex brain region: frontal lobe general functions: intellectual functions; affective processes associated disorder(s): intellectual and emotional impairment

Broca's motor speech area

cerebral cortex brain region: frontal lobe general functions: regulates motor aspects of speech associated disorder(s): motor aphasia

precentral gyrus

cerebral cortex brain region: frontal lobe general functions: voluntary movement of muscles of body and head region associated disorder(s): loss of voluntary movement of body and head region

upper and lower banks of calcarine sulcus

cerebral cortex brain region: occipital lobe general functions: visual perception associated disorder(s): partial or total loss of vision of the contralateral visual fields for both eyes; depending upon the extent of the lesion in the visual cortex

postcentral gyrus

cerebral cortex brain region: parietal lobe general functions: conscious perception of somesthetic sesnation associated disorder(s): loss of somatosensory perception

Superior parietal lobule

cerebral cortex brain region: parietal lobe general functions: integration of sensory and motor functions; programming mechanism for motor responses associated disorder(s): posterior parietal syndrome; sensory neglect; apraxia

Wernicke's area

cerebral cortex brain region: parietal lobe general functions: receptive integration of speech associated disorder(s): receptive aphasia

superior temporal gyrus

cerebral cortex brain region: temporal lobe general functions: auditory perception associated disorder(s): loss of auditory perception

middle temporal gyrus

cerebral cortex brain region: temporal lobe general functions: detection of moving objects associated disorder(s): loss of facial recognition

inferior temporal gyrus

cerebral cortex brain region: temporal lobe general functions: recognition of faces associated disorder(s): loss of facial recognition

A patient exhibits clumsiness, weakness, and somatosensory loss of the right leg. The most likely cause of these symptoms is a: a) Seizure of the left frontal lobe b) Tumor of the left prefrontal cortex c) Tumor of the right cerebellar hemisphere d) Hemorrhagic stroke of the left anterior cerebral artery e) Left frontal lobe concussion resulting from an automobile accident

d) Hemorrhagic stroke of the left anterior cerebral artery The anterior cerebral artery supplies, in part, the motor and somatosensory neurons associated with the leg region of the cerebral cortex. A stroke involving the left anterior cerebral artery will damage neurons in the left medial sensorimotor region, thus causing weakness and loss of sensation in the right leg. The other choices are incorrect because they involve different regions of the cerebral cortex that are not involved in sensorimotor regulation of the leg region.

A 25yo woman complained to her neurologist of a sudden onset of blurred vision, loss of visual acuity, and loss of color vision in her right eye. The patient also experienced pain behind her right eye. The neurologist suspected that this was a case of optic neuritis and ordered an MRI, which showed changes consistent with demyelinating disease. The optic neuritis with this history was associated with which one of the following disorders? a) Myasthenia gravis b) Lambert-Eaton syndrome c) Guillain-Barré syndrome d) Multiple sclerosis e) Cystic fibrosis

d) Multiple sclerosis In patients with MS, demyelination of axons in the optic nerves, brain, and spinal cord occurs. Therefore neural conduction in the CNS is disrupted. In Guillain-Barré syndrome, however, demyelination occurs in peripheral nerves, innervating the muscles and skin. In the other syndromes listed, demyelination of axons does not occur.

An elderly female patient was brought into the ED after suffering injuries to her head and body as a result of falling in her bathroom. A routine neurologic examination revealed that she would lose her balance when attempting to walk and would tend to fall to one side. She also showed very poor coordination in the use of her right arm and further displayed a tremor when attempting to produce a purposeful movement with that arm. The most likely locus of the lesion is: a) basilar pons b) lateral aspect of the caudal pontine tegmentum c) lateral aspect of the rostral pontine tegmentum d) cerebellum e) midline region of the tegmentum and basilar aspects of pons

d) cerebellum The cerebellum is concerned with the control of motor functions, and lesions of this structure can cause a variety of motor deficits, including loss of balance and coordination and tremoer in attempting to move the limb. Lesions of other regions of the pons would produce different motor deficits, such as an upper motor neuron paralysis, associated with damage to the corticospinal tract

A magnetic resonance image scan taken of a 60yo woman revealed the presence of a tumor on the base of the brain that was situated just anterior to the pituitary and the impinged upon the adjoining neural tissue. A likely deficit resulting from this tumor includes: a) loss of movement of upper limbs b) speech impairment c) difficulties in breathing d) changes in emotionality e) loss of ability to experience pain

d) changes in emotionality The optic nerve enters the brain at the level of the far anterior hypothalamus. Tumors of this region of the base of the brain commonly affect the hypothalamus, which plays an important role in the regulation of emotional behavior and autonomic functions. Such tumors would also likely affect visual functions. Movements of the limbs are affected by lesions of the internal capsule or precentral gyrus; speech impairment is affected by damage to the inferior frontal or superior temporal gyrus; breathing is affected by the lower brainstem; and pain is affected by parts of the brainstem, thalamus, and postcentral gyrus.

A 43yo woman had herself admitted to the hospital after complaining of headaches. Two days later, she was unable to move either of her hands or feet and was, in effect, a quadriplegic. A neurologic examination revealed no loss of either cranial nerve reflexes or sensation from the body or head. Subsequent MRI and other neurologic diagnoses indicated that the damage to the CNS was quite limited. The most likely focus of the lesion was in the a) dorsomedial aspect of the rostral medulla b) dorsolateral aspect of the rostral medulla c) ventromedial aspect of the rostral medulla d) midline at the border of medulla and spinal cord e) dorsomedial aspect of the border of medulla and pons

d) midline at the border of medulla and spinal cord The decussation of the pyramids occurs at the most caudal aspect of the medulla near its border with the spinal cord. Therefore, damage to the midline region would most likely affect corticospinal fibers that arise from both sides of the cerebral cortex and that normally pass to both the cervical and lumbar levels on both sides of the spinal cord. The net results here would result in an upper motor neuron paralysis of all four limbs. The position of the decussation of the pyramids is the only locus where a single lesion (among the choices presented) could affect pyramidal fibers bilaterally. Therefore, the other choices are incorrect because lesions at any of these other sites could not affect pyramidal fibers bilaterally (i.e. ventromedial medulla) or at all with respect to several choices (i.e. dorsolateral and dorsomedial aspects of the caudal or rostral medulla)

An 80yo man was brought to the ED after complaining of an inability to swallow food. The structure most closely linked to this dysfunction is: a) inferior olivary nucleus b) pyramids c) spinal trigeminal nucleus d) nucleus ambiguus e) hypoglossal nucleus

d) nucleus ambiguus Swallowing is controlled by neurons of the 9th and 10th cranial nerves, which innervate the pharyngeal and laryngeal muscles. These neurons arise from the nucleus ambiguus, which contributes to the motor outputs of both cranial nerves. The inferior olivary nucleus serves as a relay for information from the spinal cord and red nucleus that is transmitted to the cerebellum, and thus, plays no role in swallowing. The pyramids at the level of the medulla contain mostly corticospinal fibers that control movements of the limbs. The spinal trigeminal nucleus receives inputs from the face associated mainly with pain and temperature. The hypoglossal nucleus regulates movements of the tongue.

The membranes that lines the cisterns in the cranial cavity are: a) dura and arachnoid mater b) dura mater and ependymal cell layer c) neuronal cell membrane ad the pia mater d) pia and arachnoid mater e) periosteal and meningeal layers of dura mater

d) pia and arachnoid mater The cisterns are formed by enlargements of subarachnoid space located between the pia and arachnoid mater. Other choices listed are not appropriate. For example, there is no space between the dura and arachnoid mater. Ependymal cells line the ventricles. there is no space between the pia and brain tissue; the pia mater is tightly attached to the brain. The periosteal and meningeal layers of the dura mater are fused except at the places where venous sinuses are located

A 27yo man was involved in a street brawl, and during the fight, he was stabbed in the back. HE lost consciousness and was rushed to the mergency room of a local hospital. After regaining consciousness, the patient received a neurologic examination. The patient indicated to the neurologist that he could not feel any pricks of a safety pin when tested along a band of an approximately 4-cm ring, which included both sides of his back. The patient was able to recognize tactile stimulation when tested on his arms and legs of both sides of the body as well as on the back or chest. Motor functions appeared to be intact. The neurologist concluded that the patient suffered damage of the: a) substantia gelatinosa b) dorsal root ganglion of the left side c) lateral funiculus of both the lumbar and thoracic cords of the left side d) region surrounding the central canal of thoracic cord e) dorsal columns at the level of thoracic cord, bilaterally

d) region surrounding the central canal of thoracic cord Bilateral segmental loss of pain is the result of damage to the region surrounding the central canal of the spinal cord. This is due to damage to the crossing fibers of the lateral spinothalamic tracts (on each side) at a specific level of the cord. Damage to the substantia gelatinosa or dorsal root ganglia could only account for unilateral loss of pain. Damage to the lateral funiculus at both lumbar and thoracic levels on one side would likewise not account for bilateral loss of pain and, additionally, such a lesion would not be segmental. Dorsal column lesions would not affect the pathways mediating pain but, instead, would affect conscious proprioception.

Which of the following statements is correct concerning directly gated transmission at the nerve-muscle synapse? a) the presynaptic boutons include synaptic vesicles containing norepinephrine b) norepinephrine released from the presynaptic terminal acts on alpha-adrenergic receptors located at the end-plate c) the transmitter-gated ion channel at the end-plate is permeable only to calcium d) voltage-gated channels selective for sodium are present in the junctional folds of the muscle-cell membrane e) each muscle fiber receives both excitatory and inhibitory inputs

d) voltage-gated channels selective for sodium are present in the junctional folds of the muscle-cell membrane At the neuromuscular junction, many varicosities (swellings), called synaptic boutons, are present at the terminals of the presynaptic neuron. The presynaptic boutons include the synaptic vesicles that contain ACh. When the motor axon is stimulated, ACh is released, which acts on the nicotinic cholinergic receptors located at the crest of the junctional folds to produce an end-plate potential (EPP). During the EPP, sodium flows into the postsynaptic cell, while potassium flows out of the cell (the transmitter-gated ionic channel at the end-plate is permeable to both sodium and potassium). In the junctional folds, the muscle cell membrane has a high density of voltage- gated channels that are selective for sodium; these channels convert the EPP into an AP in the muscle fiber that eventually results in muscle contraction. The muscle fibers receive only excitatory inputs.

A 67-year-old woman complained to her ophthalmologist that she was experiencing double vision. After a thorough examination, the patient was given a neurologic examination. A magnetic resonance imaging scan revealed the presence of a small stroke. The most likely locus of the lesion was the: a. Ventrolateral medulla b. Dorsomedial medulla c. Dorsolateral pons d. Dorsomedial pons e. Dorsolateral midbrain

d. Dorsomedial pons The paramedian reticular formation of the caudal pons in the region of the abducens nucleus contains the horizontal gaze center. It serves to integrate cortical and vestibular inputs for the control of conjugate horizontal gaze. Damage to this region would result in loss of coordination of the eyes, causing double vision. The other choices involve regions that are not associated with the regulation of eye movements. Damage to these regions would cause significantly different neurologic deficits that are unrelated to double vision.

During what appeared to be routine surgery for a torn ligament, a middle-aged man suffered a stroke. After a few days, the patient showed some recovery because he was able to walk with some difficulty, and, in addition, sensory functions seemed normal. However, a neurologic evaluation revealed a weakness in muscles that regulate breathing, speech, swallowing, and facial expression. A subsequent magnetic resonance imaging scan indicated that the stroke was limited but primarily affected the: a. Premotor cortex b. Medullary pyramids c. Posterior limb of internal capsule d. Genu of internal capsule e. Anterior limb of internal capsule

d. Genu of internal capsule The symptoms described in this case reflect pseudobulbar palsy, which is characterized by weakness in the muscles of the head and face. It involves corticobulbar pathways that innervate, in part, cranial nerve motor nuclei. These fibers are contained in the genu of the internal capsule. Damage to the premotor cortex would produce a form of apraxia. Damage to the medullary pyramids is too low to affect corticobulbar fibers, which supply the facial nerve. The posterior limb of the internal capsule contains corticospinal fibers, which have no influence on brainstem cranial nerve activity. The anterior limb of the internal capsule contains frontopontine fibers, which synapse with pontine nuclei in the basilar pons and, thus, constitute part of a circuit linking the cerebral and cerebellar cortices. Accordingly, this pathway is not related to functions of cranial nerve motor nuclei.

A 60-year-old man was admitted to the local hospital after complaining that, for the past few months, he has had difficulty in swallowing and his voice has become increasingly hoarse and, at times, little or no voice could be produced. The patient was given a neurologic and general medical examination, and a magnetic resonance imaging scan (MRI) was done. The examinations revealed deviation of the uvula to one side and significant reduction of gastric fluids. The MRI revealed the presence of a growing tumor. The location of this tumor is in the: a. Ventromedial medulla b. Dorsolateral pons c. Internal acoustic meatus d. Jugular foramen e. Hypoglossal canal

d. Jugular foramen The jugular foramen contains fibers of cranial nerves (CN) IX and CN X. In particular, damage to fibers associated with CN X could account for both the somatomotor and autonomic effects described in this case. Because CN X innervates the intrinsic muscles of the larynx, damage to the nerve would affect swallowing and speech (producing hoarseness). Reduction in gastric secretions is due to damage to the parasympathetic inputs to the stomach from the vagus nerve. The other choices are not appropriate because none of them contain any fibers or cell bodies associated with CN X.

A patient displays ipsilateral medial gaze paralysis coupled with contralateral hemiplegia. The lesion is located in the: a. Medulla b. Caudal pons c. Rostral pons d. Midbrain e. Diencephalon

d. Midbrain Medial gaze is governed by the action of the oculomotor (cranial nerve [CN] III) nerve. This nerve passes close to the crus cerebri en route to exiting the brain. Therefore, a lesion located in the ventromedial aspect of the midbrain can quite easily affect both the root fibers of CN III as well as the descending fibers of the corticospinal tract. Such a lesion would produce paralysis of the limbs on the contralateral side of the body, due to the disruption of the corticospinal tract, and ipsilateral third nerve paralysis. This constellation of deficits is called Weber's syndrome.

A middle-aged man was admitted to a local hospital with a cerebellar hemorrhage resulting from hypertension. Several days later, the patient displayed "past pointing" and "asynergia of movement." 2) The region affected by the hemorrhage is one that shares direct or indirect connections with: a. Vestibular nuclei b. Reticular formation c. Fastigial nucleus d. Motor regions of cerebral cortex e. Sensory regions of spinal cord

d. Motor regions of cerebral cortex The cerebellar hemisphere is linked anatomically and functionally (in a reciprocal manner) with motor regions of the cerebral cortex. The vestibular nuclei, reticular formation, and fastigial nucleus are all associated anatomically and functionally with more medial (vermal and paravermal) regions of the cerebellar cortex. Likewise, the relationship of the cerebellar hemisphere with sensory regions of the spinal cord is very indirect, if existent.

Central control of cardiovascular function is mediated primarily from the: a. Prefrontal cortex b. Dorsomedial pons c. Ventromedial medulla d. Ventrolateral medulla e. Midbrain tectum

d. Ventrolateral medulla The ventrolateral medulla gives rise to neurons that project to the intermediolateral cell column of the thoracolumbar spinal cord. In this manner, this region of the medulla regulates sympathetic activity. The prefrontal cortex may exert some influence on autonomic functions; the primary properties of this region are associated with intellectual and affective functions. The dorsomedial pons, ventromedial medulla, and tectum are not known to contain fiber systems that directly affect autonomic functions.

caudate nucleus, putamen, globus pallidus, subthalamic nucleus, substantia nigra

deep brain structures brain region: basal ganglia general functions: regulation of motor functions associated with cerebral cortex associated disorder(s): dyskinesia

lateral, third, and fourth ventricles and cerebral aqueduct

deep brain structures brain region: ventricles of the brain general functions: flow of CSF throughout the CNS: a source of electrolytes and conduit of neuroactive and metabolic products associated disorder(s): hydrocephalus

hypothalamic nuclei

diencephalon brain region: hypothalamus general functions: visceral (feeding, drinking, autonomic, and endocrine functions and sexual and emotional behavior) associated disorder(s): disruption, loss, or alterations in visceral and affective functions and processes

Which one of the following statements regarding the circle of Willis is correct? a) It is the primary source of blood supply to the pons and medulla. b) It includes two vertebral arteries. c) It is the site where most of the cerebrospinal fluid is formed. d) The superior cerebellar artery arises from this circle of arteries. e) It surrounds the optic chiasm, tuber cinereum, and the interpeduncular region.

e) It surrounds the optic chiasm, tuber cinereum, and the interpeduncular region. The cerebral arterial circle (circle of Willis) surrounds the optic chiasm and the infundibulum of the pituitary. It is formed by the anastomosis of the branches of the internal carotid artery and the terminal branches of the basilar artery. The arteries that form the circle of Willis include the anterior communicating artery, posterior communicating arteries, and the posterior cerebral arteries. Vertebral and superior cerebellar arteries are not included in the circle of Willis, which, under normal circumstances, does not supply blood to the pons and medulla. When the circle of Willis is patent (20% of individuals), it sup- plies the hypothalamus, hypophysis, infundibulum, thalamus, caudate nucleus, putamen, internal capsule, globus pallidus, choroid plexus (lateral ventricles), and temporal lobe. The choroid plexuses produce about 70% of the cerebrospinal fluid present in the brain and spinal cord.

During routine surgery for appendicitis, a clot is released from the lung of a 75yo man, causing the patient to remain unconscious for a period of 1 week. Upon regaining consciousness, the patient finds that he is unable to maintain his balance and, further, displays tremors while attempting to produce a purposeful movement. In addition, the patient's movements are not smooth but jerky and lack coordination. The region affected most likely include the: a) spinal cord b) medulla c) pons d) midbrain e) cerebellum

e) cerebellum Although the spinal cord, medulla, pons, and midbrain play important roles in motor functions, the primary functions of the cerebellum include regulation of motor functions. Damage to parts of this structure causes a loss of balance, loss of coordination of movements, and tremors. Unlike the cerebellum, none of the other regions has a direct role in the regulation of these processes

Which of the following statements is correct regarding the sodium-potassium pump? a) binding sites for ATP are located on the extracellular side of the pump b) it drives more positive charge into the neuron c) binding sites for K+ ions are located on the cytoplasmic side of the pump d) it pumps out two Na+ ions and pumps 3 K+ ions into the neuron e) it pumps three Na+ ions out of the neuron and pumps in two K+ ions

e) it pumps three Na+ ions out of the neuron and pumps in two K+ ions The sodium-potassium pump is located in the neuronal membrane. Binding sites for ATP and Na+ ions are located on the cytoplasmic side. It pumps out three Na+ ions for the two K+ ions it pumps in. Thus, it drives, more positive charge out of the cell than it brings into the cell. The binding site for K+ is located on the extracellular side of the pump.

As a result of a vascular lesion of the brainstem, an afflicted individual displays a rather extensive marked rigidity in his limbs. The pathway most likely responsible for this rigidity is the: a) medial longitudinal fasciculus b) rubrospinal tract c) tectospinal tract d) lateral reticulospinal tract e) lateral vestibulospinal tract

e) lateral vestibulospinal tract Impulses transmitted to the spinal cord by the lateral vestibular nucleus powerfully *facilitate* ipsilateral extensor motor neurons and increase extensor motor tone. The main function of this tract is to control the muscles that maintain upright posture and balance. The descending fibers of the medial longitudinal fasciculus do not descend beyond the cervical level and have no effect on functions of the lower limbs. The rubrospinal tract is known to facilitate the flexor musculature, and the lateral reticulospinal tract inhibits spinal reflex activity. Damage to the tectospinal tract does not produce rigidity. The tectospinal tract is believed to aid in directing head movements in response to visual and auditory stimuli.

A security guard at a bank was shot in the back during an attempted bank robbery. He was admitted to the emergency room, and when he regained consciousness, he was given a neurologic examination. The patient indicated that he could not detect tactile stimulation of the left leg, although sensation in the left arm after similar stimulation was intact. When a pinprick was applied to all four limbs, the patient said that he could not feel the sensation in his right leg, whereas this sensation was present in his left leg and both arms. In addition, further neurologic examination indicated that the patient could not move his left leg. The neurologist concluded that there was damage to the: a) dorsal horn of the right side of the thoracic cord b) region surrounding the central canal of the lumbar cord c) region of the dorsal columns, bilaterally d) ventral horn of the left side of the thoracic cord e) left half of the lower thoracic cord

e) left half of the lower thoracic cord This disorder is a classic example of Brown-Séquard syndrome, in which there is damage to one side of the spinal cord. Such a lesion would cause loss of conscious proprioception below the lesion on the same side (i.e., left leg in this case) and loss of pain in the contralateral limb below the lesion (i.e., right leg). Sensation from other regions would remain intact. Because of the damage to the ventral horn and lateral funiculus, there would be loss of ability to move the limb at the level of the lesion or below it (i.e., left leg). A dorsal horn lesion of the right side could not account for the loss of sensation on the left side. Damage to the region of the central canal would only produce loss of pain bilaterally and segmentally. Damage to the dorsal columns would only affect conscious proprioception but not pain. A ventral horn lesion would not affect sensory functions, such as pain and conscious proprioception.

A neuronal cell group that responds directly to activation of muscle spindles from the jaw is: a) the facial motor nucleus (cranial nerve VII) b) the spinal nucleus of cranial nerve V c) the main sensory nucleus of cranial nerve V d) the motor nucleus of cranial nerve V e) the mesencephalic nucleus of cranial nerve V

e) the mesencephalic nucleus of cranial nerve V The mesencephalic nucleus of cranial nerve (CN) V contains cell bodies of first-order neurons whose peripheral receptors are muscle spindles contained in muscles of the head, which respond to stretching of one of these muscles. The alternate choices relate to other sensory modalities (main sensory or spinal nucleus of CN V) or to structures mediating motor functions (motor nucleus of CN V or CN VII)

Specialized cells in the ventral aspect of the midbrain are a major source of: a. Enkephalin to the basal forebrain b. Serotonin to the limbic system c. Norepinephrine to the cerebral cortex d. Serotonin to the spinal cord e. Dopamine to the neostriatum

e. Dopamine to the neostriatum Neurons in the pars compacta of the substantia nigra, situated ventrally in the midbrain just above the crus cerebri, give rise to dopaminergic neurons that project to the neostriatum. Norepinephrine neurons are located in the pons and medulla, serotonin neurons are located in a dorsomedial position within the raphe complex of the brainstem, and enkephalinergic neurons are located in the periaqueductal gray matter.

Which one of the following arteries supplies the cranial dura? a. Posterior communicating artery b. Anterior choroidal artery c. Posterior cerebral artery d. Ophthalmic artery e. Middle cerebral artery

e. Middle cerebral artery The primary artery blood supply to the dura is provided by the middle meningeal artery

A patient was admitted to the hospital and examined by a neurologist, who made the following report. When the patient was asked to look to the left, the right eye deviated to the right. Likewise, when looking straight ahead, the right eye deviated to the right. The patient also reported having double vision and had difficulty in focusing on an object when it was placed close to him. In addition, the patient was unable to move his left arm or leg. The neurologist concluded that there was damage to the midbrain that was localized to the: a. Reticular formation b. Superior colliculus c. Nucleus of cranial nerve III d. Lateral aspect of midbrain e. Ventromedial aspect of midbrain

e. Ventromedial aspect of midbrain Lesions involving the ventromedial aspect of the midbrain at the level of cranial nerve (CN) III (and superior colliculus) would likely cause damage to both the corticospinal tracts (situated in the crus cerebri) and fibers (not nucleus) of CN III, which pass ventromedially to exit through the floor at this level of the midbrain. Therefore, damage to these structures would result in both an upper motor neuron paralysis of the contralateral limbs and an ipsilateral loss of functions associated with CN III (see explanation to question 2). Damage to the other regions of the midbrain that were provided as alternate choices would be incorrect because they do not include these two structures.