neuroanatomy Flashcards

Question

2. The optic chiasm is supplied by all of the following arteries EXCEPT the (A) internal carotid artery (B) anterior communicating artery (C) anterior choroidal artery (D) posterior communicating artery (E) anterior cerebral artery

Answer 1

(C) anterior choroidal artery

Answer 2

(B) posterior cerebral artery

Answer 3

(A) enters the skull via the sphenoid bone

Answer 4

(B) gives rise to the labyrinthine artery

Answer 5

(D) optic nerve

Answer 6

(A) enters the orbit via the superior orbital fissure

Answer 7

(E) it supplies the dura of the posterior cranial fossa

Answer 8

(C) Fourth

Answer 9

(B) anencephaly

Answer 10

(C) Arnold-Chiari syndrome

Answer 11

(C) pontine flexure

Answer 12

(B) It is located between the alar and basal plates

Answer 13

(C) globus pallidus

Answer 14

(D) adenohypophysis

Answer 15

(D) nucleus ambiguus

Answer 16

(E) is completed by birth

Answer 17

(C) spina bifida usually occurs in the cervi-cothoracic region

Answer 18

(C) contains the neural crest

Answer 19

(E) myelencephalon

Answer 20

(B) ohgodendrocytes

Answer 21

(B) 3 mm/day

Answer 22

(C) 15 m/sec

Answer 23

(E) bipolar neurons are the most common type of neuron

Answer 24

(D) contain rough endoplasmic reticulum

Answer 25

(A) it is produced by the microglia

Answer 26

(C) they are considered to be the scavenger cells of the CNS

Answer 27

(B) they are derived from the neural tube

Answer 28

(A) they are derived from the neural crest

Answer 29

(C) it is a retrograde degeneration

Answer 30

(B) mitochondria are transported at the rate of 5 mm/day

Answer 31

(A) pain and thermal receptors utilize group lb fibers

Answer 32

(E) it is greatly reduced in size at sacral levels

Answer 33

(E) It lies within the subarachnoid space

Answer 34

(B) It is found at the level of the phrenic nucleus

Answer 35

(D) it terminates in the newborn at VS2

Answer 36

(D) all spinal nerves have white communicating rami

Answer 37

(D) it is derived from the pia

Answer 38

(E) the cell body of afferent nerve fiber is found in the dorsal horn

Answer 39

(B) Dorsal column

Answer 40

(C) they descend through the anterior limb of the internal capsule

Answer 41

(B) it enters the cerebellum via the superior cerebellar peduncle

Answer 42

(E) It plays a role in the control of extensor tone

Answer 43

(D) Babinski's sign

Answer 44

(D) dorsal spinocerebellar tract

Answer 45

(A) prefrontal cortex

Answer 46

(C) it projects to the ventral posteromedial (VPM) nucleus of the thalamus

Answer 47

(C) it decussates in the spinal cord

Answer 48

(B) usually is found at lumbosacral levels

Answer 49

(E) is characterized by lower motor neuron (LMN) symptoms

Answer 50

(A) plantar response flexor on the left side

Answer 51

(D) cauda equina syndrome

Answer 52

(E) plantar reflex extensor

Answer 53

(C) it affects dorsal root ganglion cells

Answer 54

(A) plantar reflexes are usually extensor

Answer 55

(E) Nucleus ambiguus

Answer 56

(B) Caudal midbrain

Answer 57

(B) arcuate nuclei

Answer 58

(B) it contains the medial longitudinal fasciculus (MLF)

Answer 59

(B) it gives rise to the dorsal trigeminothalamic tract

Answer 60

(B) it contains the facial nucleus

Answer 61

(A) it gives rise to SVE fibers

Answer 62

(C) it exits the brainstem at the superior pontine sulcus

Answer 63

(A) it plays a role in the corneal reflex

Answer 64

(E) it innervates a muscle that extorts the globe

Answer 65

(B) its neurons contain dopamine

Answer 66

(A) stimulation of its parasympathetic component results in mydriasis

Answer 67

(D) Glioma of the lateral medulla

Answer 68

(D) it is the afferent limb of the jaw jerk reflex

Answer 69

(E) first-order neurons are located in the mesencephalic nucleus

Answer 70

(B) the posterior belly of the digastric muscle

Answer 71

(B) anesthesia of the tongue

Answer 72

(D) it is more common in men than in women

Answer 73

(C) it contains bipolar ganglion cells

Answer 74

(D) it innervates the skin of the dorsum of the nose

Answer 75

(D) it contains bipolar neurons

Answer 76

(C) it mediates the corneal reflex

Answer 77

(D) it is located in the medulla and pons

Answer 78

(C) it innervates the stapedius muscle

Answer 79

(E) destruction of the principal sensory nucleus of CN V

Answer 80

(C) it is abolished by a transection of the spinal trigeminal tract made within its caudal medullary extent

Answer 81

(B) it may be the result of an acoustic neuroma

Answer 82

(B) it may result from a middle ear infection

Answer 83

(C) inferior olivary nucleus

Answer 84

(D) it detects sound frequencies from 20 Hz to 50 kHz

Answer 85

(E) it receives sensory innervation by the vagal nerve

Answer 86

(E) it is a structure of the middle ear

Answer 87

(D) it gives rise to the tectorial membrane

Answer 88

(A) cochlear nuclei

Answer 89

(B) marijuana

Answer 90

(Dj macula of the utricle

Answer 91

(D) Deviation of the eyes to the left

Answer 92

(D) it detects sound frequencies from 20 Hz to 50 kHz

Answer 93

(B) it is considered to be alpha rigidity

Answer 94

(A) the patient would have a vertical nystagmus

Answer 95

(A) it is found in the helicotrema

Answer 96

(D) Caloric testing is contraindicated in comatose patients

Answer 97

(D) They are found within the vestibule

Answer 98

(B) hair cells of the semicircular ducts are stimulated by perilymphatic flow

Answer 99

(E) it is tested clinically by caloric stimulation

Answer 100

(A) it lies within the bony modiolus

Answer 101

(A) they are three in number

Answer 102

(E) it is a crossed pathway

Answer 103

(E) transection results in paralysis of convergence

Answer 104

(E) it results in nystagmus to the same side with ice-water irrigation of the external auditory meatus

Answer 105

(E) it is located in the paracentral lobule 212

Answer 106

B. The mandibular nerve (CN V-3) does not pass through the cavernous sinus; it exits the skull via the foramen ovale.

Answer 107

B.The trigeminal nerve (CN V) contains only special visceral efferent (SVE) and general somatic afferent (GSA) fibers.

Answer 108

E. The optic nerve (CN II) enters the skull via the optic canal. The optic canal also contains the ophthalmic artery.

Answer 109

C. Transection of the oculomotor nerve (CN III) does not interrupt the afferent limb of the pupillary reflex, which is bilateral. Light shone into the left eye results in constriction of the contralateral pupil, the consensual reaction.

Answer 110

D. The right trochlear nucleus of CN IV projects to the left superior oblique muscle. Diplopia occurs when an image falls on disparate parts of the retina. The pupillary light reflex is mediated by the parasympathetic fibers of the oculomotor nerve. 231

Answer 111

E. The vestibulocochlear nerve (CN VTII) is classified as a special somatic afferent (SSA) nerve, as is the optic nerve (CN II).

Answer 112

D. The vagal nerve (CN X) emerges from the brainstem in the postolivary sulcus of the medulla and exits the skull via the jugular foramen with CN LX and CN XI. It contains preganglionic parasympathetic fibers from the nucleus ambiguus that project to the cardiac ganglia of the heart. The vagal nerve innervates the levator veli palatini muscle, which raises and retracts the soft palate. The dorsal motor nucleus of the vagal nerve lies in the medulla.

Answer 113

D. The geniculate ganglion contains all of the first-order sensory neurons of the facial nerve (CN VII) [general somatic afferent (GSA) and special visceral afferent (SVA)]. It is found within the temporal bone and gives rise to the greater petrosal nerve. Sensory neurons in the geniculate ganglion innervate taste buds from the anterior two-thirds of the tongue. Taste fibers from the posterior third of the tongue belong to the glossopharyngeal nerve (CN LX). Pseudounipolar ganglion cells of the geniculate ganglion innervate part of the outer ear.

Answer 114

D. The olfactory nerve (CN I), a special visceral afferent (SVA) nerve, consists of the unmyelinated axons of bipolar neurons found in the olfactory epithelium of the upper nasal cavity. There are 25 million neurosensory cells on each side. These axons synapse with mitral cells in the olfactory bulb, a rhinencephalic structure of the forebrain. Mitral cells project directly via the olfactory tract to the primary olfactory cortex of the uncus.

Answer 115

A. The optic nerve (CN II) enters the skull via the optic canal of the sphenoid bone (the ophthalmic artery is also found in the optic canal). Efferent retinal fibers are the afferent limb of the pupillary light reflex. The efferent limb is the oculomotor nerve (CN III). The optic nerve is invested with meninges and lies in the subarachnoid space. The optic nerve is a tract of the central nervous system (CNS) and not a peripheral nerve. There is no regeneration after transection. The axons of the optic nerve are myelinated by oligodendrocytes; peripheral nerve axons are myelinated by Schwann cells.

Answer 116

D. The oculomotor nucleus is found in the rostral midbrain at the level of the superior colliculus. Ptosis results after transection of the fibers to the levator palpebrae muscle. The oculomotor nerve (CN III) traverses the wall of the cavernous sinus with CN IV, CN VI, CN V-l, and CN V-2. The oculomotor nerve has a general visceral efferent (GVE) parasympathetic component, which arises from the Edinger-Westphal nucleus. CN III exits the cranium via the superior orbital fissure.

Answer 117

C. The accessory (spinal) nerve (CN XI) exits the skull via the jugular foramen (with CN LX and CN X). The spinal part of the spinal accessory nerve enters the skull via the foramen magnum. CN XI contains SVE fibers from the nucleus ambiguus that innervate intrinsic muscles of the larynx; CN XI contains special visceral efferent (SVE) fibers from the cervical spinal cord that innervate two muscles of branchiomeric origin, the trapezius and the sternocleidomastoid. The dorsal motor nucleus is the general visceral efferent (GVE) nucleus of the vagal nerve (CN X).

Answer 118

E. The facial nerve (CN VII) provides the preganglionic parasympathetic innervation for the lacrimal, sublingual, and submandibular glands and innervates the stapedius muscle of the tympanic cavity and the posterior belly of the digastric muscle. The otic ganglion receives preganglionic parasympathetic input from the glossopharyngeal nerve (CN LX) and projects postganglionic parasympathetic fibers to the parotid gland.

Answer 119

E. The trigeminal nerve (CN V) [general somatic afferent (GSA) and special visceral efferent (SVE)] innervates the tensor tympani muscle and the anterior belly of the digastric muscle. It innervates the supratentorial dura. The skin over the angle of the jaw and the scalp of the back of the head are innervated by the second and third cervical nerves. 232

Answer 120

B. Transection of the glossopharyngeal nerve (CN IX) results in degeneration of neurons in the rostral part of the nucleus ambiguus and in the inferior salivatory nucleus, loss of the gag reflex, loss of sensation from the tonsillar bed, loss of taste and pain sensation from the posterior third of the tongue, and loss of the carotid sinus reflex. The superior salivatory nucleus is a general visceral efferent (GVE) nucleus of CN VH.

Answer 121

B. The lesion is a classic Wallenberg's syndrome (PICA syndrome) of the lateral medullary zone. Interruption of the descending sympathetic tract produces ipsilateral Horner's syndrome. Involvement of the nucleus ambiguus or its exiting intra-axial fibers accounts for lower motor neuron (LMN) paralysis of the larynx and soft palate. The ipsilateral facial anesthesia is due to interruption of the spinal trigeminal tract; the contralateral loss of pain and temperature sensation from the trunk and extremities is due to transection of the spinothalamic tracts. The combination of ipsilateral and contralateral sensory loss is called alternating hemianesthesia. Singultus (hiccup) is frequently seen in this syndrome and is thought to result from irritation of the reticulophrenic pathway.

Answer 122

D. This constellation of deficits constitutes Weber's syndrome, which affects the basis pedunculi and the exiting intra-axial oculomotor fibers. Severe ptosis (compare mild ptosis of Horner's syndrome), the abducted and depressed eyeball, and the internal ophthalmoplegia (fixed dilated pupil) are third nerve signs. The contralateral hemiparesis results from interruption of the corticospinal tracts; lower facial weakness is due to interruption of the corticobulbar tracts. The combination of ipsilateral and contralateral motor deficits is called alternating hemiplegia. In cases of sensory or motor long tract involvement, the involved cranial nerve indicates the rostrocaudal site of the lesion; the cranial nerve signs are ipsilateral and lateralize the lesion (the trochlear nerve is the exception).

Answer 123

E. These signs point to the base of the pons (medial inferior pontine syndrome) on the right side and include involvement of the exiting intra-axial abducent fibers that pass through the uncrossed corticospinal fibers; this results in an ipsilateral rectus paralysis [lower motor neuron (LMN) lesion] and contralateral hemiparesis. Contralateral facial weakness results from damage to the corticobulbar fibers prior to their decussation. Involvement of the transverse pontine fibers destined for the middle cerebellar peduncle results in cerebellar signs. Again, the involved cranial nerve and pyramidal tract indicate where the lesion must be to account for the deficits. An ipsilateral sixth nerve paralysis and crossed hemiplegia is called the Millard-Gubler syndrome.

Answer 124

A. These deficits indicate Parinaud's syndrome, dorsal midbrain syndrome. This condition frequently is the result of a pinealoma, which compresses the superior colliculus and the underlying accessory oculomotor nuclei that are responsible for upward and downward vertical conjugate gaze. Patients usually have pupillary disturbances and absence of convergence.

Answer 125

A. This lesion site indicates medial longitudinal fasciculus (MLF) syndrome, internuclear ophthalmoplegia. The lesion is located in the dorsomedial tegmentum and is found between the abducent nucleus and the oculomotor nucleus.

Answer 126

C. These deficits correspond to a lesion in the dorsolateral zone of the pontine isthmus, lateral superior pontine syndrome. Interruption of the descending sympathetic pathway to the ciliospinal center of Budge (T1-T2) results in Horner's syndrome (always ipsilateral). Involvement of the lateral aspect (includes the leg fibers) of the medial lemniscus results in a loss of vibration sensation and other dorsal column modalities. Damage to the trigeminothalamic and spinothalamic tracts at this level results in contralateral hemianesthesia of the face and body. Infarction of the superior cerebellar peduncle leads to severe cerebellar dystaxia on the same side.

Answer 127

A. These signs indicate lateral midpontine syndrome. This lesion involves the motor and principal trigeminal nuclei and the intra-axial root fibers of the trigeminal nerve as it passes through the base of the pons. AH signs are ipsilateral and refer to CN V. The afferent limb of the corneal reflex has been interrupted. This syndrome results from occlusion of the trigeminal artery, a short circumferential branch of the basilar artery.

Answer 128

D. These signs constitute lateral inferior pontine syndrome (AICA syndrome). The neurologic findings are all signs of a lesion involving the facial nerve (CN VII). The facial nerve nucleus and intra-axial fibers are found in the caudal lateral pontine tegmentum. A lesion of the stylomastoid foramen would not include the absence of the stapedial reflex or the loss of taste sensation from the anterior two-thirds of the tongue. The stapedial nerve and the chorda tympani exit the facial canal proximal to the stylomastoid foramen.

Answer 129

D. The base of the pons includes corticospinal (pyramidal), corticobulbar, and corticopontine tracts, pontine nuclei, and transverse pontine fibers. At caudal levels, intra-axial abducent fibers of CN VI pass through the lateral pyramidal fascicles.

Answer 130

D. The anterior (ventral) spinal artery, a branch of the vertebral artery, irrigates the ventral median zone of the medulla, which includes the pyramid (corticospinal tracts), the medial lemniscus, and the exiting intra-axial root fibers of the hypoglossal nerve (CN XII). The inferior olivary nucleus lies in the paramedian zone of the medulla and is supplied by the short lateral branches of the vertebral artery.

Answer 131

C. The posterior inferior cerebellar artery (PICA), a branch of the vertebral artery, perfuses the lateral zone of the medulla, which includes the medial and inferior vestibular nuclei, the inferior cerebellar peduncle, and the lateral spinothalamic tract.

Answer 132

D. The anterior inferior cerebellar artery (AICA) usually (in 85% of cases) gives rise to the labyrinthine artery. The AICA supplies the lateral zone of the caudal pontine tegmentum (including the cochlear nuclei, the facial nucleus, and intra-axial fibers) and the spinal trigeminal nucleus and tract. The medial longitudinal fasciculus (MLF) is irrigated by paramedian penetrating branches of the basilar artery.

Answer 133

E. Internuclear ophthalmoplegia results from a lesion of the medial longitudinal fasciculus (MLF), which extends in the dorsomedial tegmentum from the abducent nucleus of CN VI to the oculomotor nucleus of CN III. Transection of the MLF results in medial rectus palsy on attempted lateral gaze and monocular nystagmus in the abducting eye. Convergence is normal. Bilateral MLF syndrome is a common ocular motor manifestation of multiple sclerosis.

Answer 134

(A) alcohol abuse Anterior vermis syndrome is a result of chronic alcohol abuse. Patients present with dystaxia of the lower limb and trunk. Posterior vermis syndrome involves the flocculonodular lobe; it is most frequently caused by an ependymoma or a medulloblastoma. Patients have truncal dystaxia. Hemispheric syndrome usually is the result of a tumor (astrocytoma) or abscess; patients have arm, leg, trunk, and gait dystaxia.

Answer 135

(A) astrocytoma ``` Astrocytomas (30%) are the most common cerebellar tumors in children; they are followed by medulloblastomas (20%) and ependymomas (10%). ```

Answer 136

(E) medulloblastoma Medulloblastomas are derived from the external granular layer of the cerebellar cortex. Medulloblastomas give rise to posterior vermis syndrome.

Answer 137

(B) ventral spinocerebellar tract The ventral spinocerebellar tract enters the cerebellum via the superior cerebellar peduncle.

Answer 138

(E) contains the juxtarestiform body The inferior cerebellar peduncle includes the restiform body and the juxtarestiform body. The juxtarestiform body contains vestibulocerebellar, cerebellovestibular, and cerebelloreticu-lar fibers.

Answer 139

(A) plays a role in the initiation, planning, and timing of voluntary motor activities The vestibulocerebellum (archicerebellum) plays a role in the maintenance of posture and balance and in the coordination of head and eye movements.

Answer 140

(B) its primary effect is on truncal and proximal muscles The red nucleus gives rise to the crossed rubrospinal tract, which has its primary effect on distal muscle groups. The red nucleus is a way station in the paravermal spinocerebellar pathway, a system dedicated to distal motor control and ongoing execution of motor acts.

Answer 141

(A) the neocerebellar pathway influences the motor cortex via the ventral anterior thalamic nucleus In the neocerebellar pathway, the dentate nucleus projects to the contralateral ventral lateral nucleus of the thalamus, which in turn projects to the motor cortex. The motor cortex gives rise to the crossed corticopontocerebellar tract, which then modifies further cerebellar output to the neocortex. The motor cortex also gives rise to the corticospinal and corticobulbar tracts. The neocerebellum thus expresses itself via the corticospinal (pyramidal) and corticobulbar (corticonuclear) tracts.

Answer 142

(C) resting static pill-rolling tremor Cerebellar signs include hypotonia, disequilibrium, muscle incoordination (dyssynergia), and nystagmus. Intention tremor is a variation of dysmetria (inability to correctly meter distances) and is commonly seen in lesions of the cerebellar hemispheres or their central projections. Dysdiadochokinesia is the inability to perform rapid alternating movements. Decomposition of movement is a breakdown of smooth muscular movement into a number of component steps. A resting static pill-rolling tremor is seen in Parkinson's disease.

Answer 143

(C) the fastigial nucleus and the emboliform nucleus are called the interposed nucleus The emboliform and globose nuclei are called the interposed nucleus. The fastigial nucleus projects to the vestibular nuclei via the uncinate fasciculus (a component of the superior cerebellar peduncle) and via the juxtarestiform body (a component of the inferior cerebellar peduncle). The dentate nucleus, the largest of the cerebellar nuclei, gives rise to the bulk of the axons in the superior cerebellar peduncle.

Answer 144

(B) contains two pairs of cerebellar peduncles The cerebellum is attached to the brainstem by three pairs of cerebellar peduncles: Superior cerebellar peduncles connect to the pons and midbrain; middle cerebellar peduncles connect to the pons; and inferior cerebellar peduncles attach to the medulla.

Answer 145

(D) receives input from the superior olivary nucleus The superior olivary nucleus is a relay nucleus of the auditory system and does not project to the cerebellum. The inferior olivary nucleus of the medulla projects to the cerebellum via the inferior cerebellar peduncle.

Answer 146

(E) is part of the brainstem The cerebellum develops from the rhombic lips of the alar plates. The metencephalon (afterbrain) consists of the pons and cerebellum; the rhombencephalon (hindbrain) includes the metencephalon and the myelencephalon (medulla oblongata). The brainstem (truncus cerebri) includes the midbrain, pons, and medulla oblongata; some authorities also include the diencephalon.

Answer 147

(D) gives rise to the fascia dentata The dentate nucleus is innervated by climbing and mossy fibers and receives inhibitory input from the Purkinje cells of the cerebellar cortex. It gives rise to most of the fibers in the superior cerebellar peduncle (i.e., the dentatorubrothalamic tract). The dentate nucleus projects to the ventral lateral and ventral posterolateral nuclei of the thalamus; these thalamic nuclei project to the motor cortex. The fascia dentata (dentate gyrus) is a structure of the hippocampal formation.

Answer 148

(C) it has an autosomal dominant mode of inheritance Friedreich's ataxia is transmitted as an autosomal recessive trait. It is the most common of the hereditary ataxias.

Answer 149

(D) the cell loss in the inferior olivary nucleus is due to a primary loss of Purkinje cells With cerebello-olivary atrophy, there is no loss of cells in the substantia nigra. With olivopontocerebellar atrophy, there is frequently a loss of neurons in the substantia nigra.

Answer 150

(C) Ventral lateral nucleus The ventral lateral nucleus receives motor input from the extrapyramidal (striatal) motor system (globus pallidus and substantia nigra) and from the cerebellum (dentate nucleus).

Answer 151

(D) Ventral posterolateral (VPL) nucleus Spinothalamic fibers project to the ventral posterolateral (VPL) nucleus, which receives the medial lemniscus.

Answer 152

(D) Ventral lateral nucleus ``` Cerebellar fibers (dentatocerebellar) project to the ventral lateral and ventral posterolateral (VPL) nuclei, which project to the motor cortex (area 4). ```

Answer 153

(A) Centromedian, ventral anterior, and ventral lateral nuclei The globus pallidus, a nucleus of the extrapyramidal (striatal) motor system, projects to three thalamic nuclei: the centromedian, the ventral anterior, and the ventral lateral nuclei of the thalamus.

Answer 154

(E) olfaction The thalamus receives precortical input from all sensory systems except the olfactory system. The olfactory pathway reaches the primary olfactory cortex (prepiriform and periamyg-daloid cortex) without a relay in the thalamus.

Answer 155

(D) is part of the extrapyramidal motor system The mediodorsal nucleus plays an important role in the expression of affect, emotion, and behavior. It is a limbic structure. The mediodorsal nucleus is not a part of the extrapyramidal motor system.

Answer 156

(D) receives input from the lateral lemniscus ``` The lateral geniculate body (LGB) receives input from the retina and projects to the visual cortex (lingual gyrus and cuneus). It is irrigated by the anterior choroidal artery and the posterior cerebral artery (thalamogeniculate arteries). The lateral lemniscus is an auditory pathway. ```

Answer 157

(E) a lesion results in a contralateral hemi-anopia The pulvinar, the largest nucleus of the thalamus, is a dorsal tier nucleus and has reciprocal connections with the visual association cortex (areas 18 and 19). The pulvinar is reciprocally connected with the parietal association cortex (areas 39 and 40). It also receives input from the superior colliculus and the pretectal area. Destruction of the pulvinar does not result in a visual field deficit (hemianopia).

Answer 158

(B) right homonymous hemianopia Infarction of the right internal capsule could result in a left homonymous hemianopia.

Answer 159

(C) Medial striate arteries A capsular stroke is most commonly caused by occlusion of the medial striate branches of the middle cerebral artery.

Answer 160

(C) results in paralysis of lateral gaze on command Interruption of the pontine medial longitudinal fasciculus (MLF) results in a medial rectus palsy on attempted conjugate lateral gaze. Convergence remains intact. This syndrome, called internuclear ophthalmoplegia or MLF syndrome, is commonly seen in multiple sclerosis.

Answer 161

(C) the midsagittal section results in binasal hemianopia The midsagittal section of the optic chiasm transects fibers from the nasal hemiretinae, resulting in a bitemporal hemianopia.

Answer 162

(D) destruction results in bitemporal hemianopia Destruction of the optic tract, the lateral geniculate body (LGB), or the geniculocalcarine tract all result in the same visual field defect, a contralateral homonymous hemianopia.

Answer 163

(C) destruction of the upper bank of the calcarine sulcus results in a lower ipsilateral homonymous quadrantanopia Destruction of the upper bank of the calcarine sulcus interrupts lateral geniculate body (LGB) fibers, which represent the upper ipsilateral retinal quadrants. The field defect is called a lower contralateral homonymous quadrantanopia.

Answer 164

(A) transection of the optic tract eliminates the direct pupillary light response Transection of the optic tract would not eliminate the direct pupillary response. Pupillary fibers in the optic tract project to the pretectal nuclei, which discharge to the ipsilateral and contralateral Edinger-Westphal nuclei.

Answer 165

(D) it is irrigated by the posterior communicating artery The superior colliculus is irrigated by the long circumflex branches of the posterior cerebral arteries (quadrigeminal arteries).

Answer 166

(C) retinal ganglion cells project directly to the visual cortex Retinal ganglion cells project to the lateral geniculate body (LGB), which projects to the primary visual cortex. Retinal ganglion cells project directly to the suprachiasmatic nucleus of the hypothalamus and to the pretectal nuclei and superior colliculus of the midbrain. The retina is derived from the optic vesicle of the diencephalon.

Answer 167

(D) contains myelinated axons from the ganglion cell layer The optic disk, the optic papilla, is found nasal (medial) to the fovea centralis. It contains no rods or cones and thus represents a blind spot in the retina. The retinal vessels emerge from the optic disk. Myelinated axons usually are not found in the retina; when they are present, they may produce a central scotoma. Myelination of the optic nerve extends from the external part of the lamina cribrosa to the lateral geniculate body (LGB).

Answer 168

(D) is the optic papilla The fovea centralis lies within the macula lutea and represents the locus of highest visual acuity. The fovea contains only cones, thus subserving color or day (photopic) vision. The fovea centralis lies temporal (lateral) to the optic disk. The optic disk is the optic papilla.

Answer 169

(B) receive direct input from the rods and cones The ganglion cells of the retina give rise to the optic nerve and project to the lateral geniculate body (LGB), the hypothalamus, the pretectal nucleus, and the superior colliculus. Input from the rods and cones is conducted to the ganglion cells via the bipolar cells. The retina is derived from the optic vesicle of the diencephalon. The hypothalamic projection is to the suprachiasmatic nucleus, a circadian pacemaker.

Answer 170

(B) it is a true peripheral nerve The optic nerve is a myelinated tract of the central nervous system (CNS) that is invested by the leptomeninges and the dura mater. Its cells of origin are found in the ganglion cell layer of the retina. It is incapable of regeneration.

Answer 171

(D) is found in the midbrain The subcortical center for lateral gaze is found in the abducent nucleus of the pons, receives input from the contralateral frontal eye field (area 8), and projects to the contralateral medial longitudinal fasciculus (MLF). Destruction of the abducent nucleus results in an ipsilateral lateral rectus paralysis and a contralateral medial rectus palsy on attempted lateral gaze. The subcortical center for vertical conjugate gaze is located in the midbrain at the level of the posterior commissure.

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