Chapter 16 Workbook Questions

Question 1

Hyperpolarization of receptor cells of the left posterior semicircular canal would be associated with depolarization (excitation) of the _____________ (right/left) ______________ (horizontal/anterior/posterior) semicircular canal.

Answer 1

Right, anterior. The anterior semicircular canal is also referred to as the superior semicircular canal.

Question 2

What are the two functional roles of the vestibular system for motor control?

Answer 2

The vestibular system plays a key role in gaze stabilization and postural control and adjustments.

Question 3

Why would a person with chronic vestibular dysfunction have a stiff neck?

Answer 3

People with chronic vestibular problems often have a stiff neck in attempt to stabilize the head and thereby lessen the symptoms of vertigo and oscillopsia.

Question 4

The medial longitudinal fasciculus is a bilateral axonal pathway between the vestibular nuclei and which of the following?
	A. Cranial nerve nuclei III, IV, and VI
	B. Superior colliculus
	C. Cranial nerve nuclei XI
	D. A and B
	E. A, B, and C

Answer 4

E: The medial longitudinal fasciculus (MLF) consists of axons that connect cranial nerves III, IV, VI, and XI and the superior colliculus. The MLF coordinates eye and head movements.

Question 5

Vestibular connections influence which of the following?
	A. Posture of the head and body
	B. Head and eye movements
	C. Consciousness
	D. Autonomic functions
	E. All of the above

Answer 5

E: The vestibular nuclei are located in the brainstem, at the junction of the pons and medulla. Projections from the vestibular nuclei contribute to sensory information about head movement and head position relative to gravity, gaze stabilization (control of eye movements when the head moves), postural adjustments, and autonomic function and consciousness.

Question 6

Information from the right visual field is conveyed to which of the following?
A. Left lateral geniculate and left visual cortex
B. Right lateral geniculate and right visual cortex
C. Bilateral geniculate then left visual cortex
D. Bilateral secondary visual cortices
E. Right pretectal area of superior colliculus

Answer 6

A: The left half of each retina receives information from the right visual field. Signals from the nasal retina of the right eye cross the midline in the optic chiasm, signals from the temporal retina of the left eye continue ipsilaterally. Thus the information from the right visual field is conveyed to the left lateral geniculate and left visual cortex.

Question 7

What is the function of the Superior colliculus

Answer 7

Visual orientation and coordination of head and eye movements

Question 8

What is the function of the Pretectal area

Answer 8

Control of pupillary reflexes

Question 9

What is the function of the Secondary visual cortex

Answer 9

Analysis of visual information for colors and motion

Question 10

What is the function of the Lateral geniculate body

Answer 10

Thalamic relay of visual information to the primary visual cortex

Question 11

What is the function of the Primary visual cortex

Answer 11

Discrimination of the shape, size, or texture of objects

Question 12

What is the function of the Posterior parietal cortex

Answer 12

Specification of movement with visual guidance

Question 13

What is the function of the Occipitotemporal region

Answer 13

Visual identification of objects

Question 14

What is the purpose of the vestibulo-ocular reflexes?

Answer 14

The vestibulo-ocular reflexes stabilize visual images during head and body movements.

Question 15

Relative to head movement, what direction do vestibulo-ocular reflexes move the eyes? Why?

Answer 15

Vestibulo-ocular reflexes move the eyes opposite to the direction of head movement to ensure that the visual field remains stable and visual fixation on objects is undisturbed.

Question 16

Is nystagmus always a sign of nervous system abnormality?

Answer 16

No, nystagmus can be evoked in a normal nervous system by rotational or temperature stimulation of the semicircular canals. Abnormal nystagmus results from unbalanced
inputs to the vestibulo-ocular reflex circuits and may be of the wrong amplitude or involve continuous ocular oscillations that occur with or without movement stimulus.

Question 17

What is the purpose of smooth pursuit eye movements?

Answer 17

Smooth pursuit eye movements allow gaze to follow a moving object.

Question 18

What types of eye movement direct gaze?

Answer 18

Saccades, smooth pursuits, and vergence eye movements direct gaze.

Question 19

Describe Ménière’s disease

Answer 19

Syndrome consisting of both auditory and vestibular disorders associated with abnormal fluid pressures of the inner ear

Question 20

Describe Dysequilibrium

Answer 20

Loss of balance

Question 21

Describe Oscillopsia

Answer 21

Loss of visual stabilization

Question 22

Describe Vertigo

Answer 22

Illusion of motion

Question 23

Describe Benign paroxysmal positional vertigo

Answer 23

Acute onset of vertigo and nystagmus in response to a rapid change of head position

Question 24

What is the most common symptom of vestibular dysfunction?
 	A. Nausea and vomiting
	B. Limb ataxia
	C. Disequilibrium
	D. Vertigo
	E. Upward beat nystagmus

Answer 24

D: The most common symptom of vestibular dysfunction is vertigo. Nausea and vomiting may occur, and disequilibrium may occur due to abnormal vestibulospinal tract signals. Limb ataxia is usually a cerebellar sign. Upward beat nystagmus is unusual and occurs with anterior semicircular canal Benign Paroxysmal Positional Vertigo (BPPV).

Question 25

What is the most common cause of near syncope?
	A. Perilymph fistula
	B. Somatosensory deficits
	C. Cardiovascular disorders
	D. Psychologic or stress disorders
	E. Motion sickness

Answer 25

C: Cardiovascular disorders are the most frequent cause of near syncope (nearly fainting). Psychologic or stress disorders are most frequently associated with light-headedness. Perilymph fistula causes hearing loss and vertigo provoked by pressure changes. Motion sickness consists of nausea, headache, anxiety, and vomiting sometimes experienced in moving vehicles.

Question 26

Damage to the right frontal eye fields may result in which deviation in visual control?
	A. Tropia
	B. Abnormal vestibulo-ocular reflexes
	C. Rotary nystagmus
	D. Ptosis
	E. Persistent ipsilateral gaze

Answer 26

E: A lesion affecting the right frontal eye fields causes both eyes to deviate ipsilaterally.

Question 27

Vertigo accompanied by sensory and/or motor loss, diplopia, and dysarthria is indicative of a lesion of which of the following?
A. Cerebellum
B. Vestibulothalamocortical pathway
C. Brainstem
D. Bilateral Benign Paroxysmal Positional Vertigo (BPPV)
E. All of the above

Answer 27

C: A brainstem lesion may cause vertigo accompanied by sensory and/or motor loss, diplopia, and dysarthria because the vestibular nuclei, medial longitudinal faciculus, oculomotor, trochlear, and abducens nuclei, and cranial nerve nuclei that control the speech muscles are located in the brainstem.

Question 28

Lateropulsion may occur with a lesion to which of the following?
	A. Parietoinsular cortex
	B. Dorsolateral medulla
	C. Inferior cerebellar peduncle
	D. Vestibular nuclei
	E. All of the above

Answer 28

E: Lesions affecting the vestibular cortex, vestibular nuclei, inferior cerebellar peduncle, or spinocerebellar tracts may produce lateropulsion. Lateropulsion is pushing toward one side of the body when sitting and/or standing.

Question 29

Which of the following are signs of the ocular tilt reaction?
	A. Lateral head tilt
	B. Skew deviation of the eyes
	C. Ocular rotation
	D. A and B
	E. A, B, and C

Answer 29

E: Lateral head tilt, skew deviation of the eyes, and ocular rotation are all signs of the ocular tilt reaction.

Question 30

The Hallpike maneuver was designed to:
A. Elicit the vestibulo-ocular reflex.
B. Rupture of the cupula.
C. Provoke maximal movement of otoconia in the horizontal semicircular canals.
D. Provoke maximal movement of otoconia in the posterior semicircular canals.
E. Treat dizziness associated with central vestibular lesions.

Answer 30

D: The Hallpike maneuver was designed to provoke maximal movement of otoconia in the posterior semicircular canals as a diagnostic test for Benign Paroxysmal Positional Vertigo (BPPV). Normally the otoconia should be confined to the macula and not in the horizontal semicircular canal. If the Hallpike maneuver elicits nystagmus and vertigo after a few seconds latency, this indicates otoconia in the horizontal semicircular canal.