Chapter 16 Workbook Questions Flashcards
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.
Right, anterior. The anterior semicircular canal is also referred to as the superior semicircular canal.
What are the two functional roles of the vestibular system for motor control?
The vestibular system plays a key role in gaze stabilization and postural control and adjustments.
Why would a person with chronic vestibular dysfunction have a stiff neck?
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.
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
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.
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
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.
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
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.
What is the function of the Superior colliculus
Visual orientation and coordination of head and eye movements
What is the function of the Pretectal area
Control of pupillary reflexes
What is the function of the Secondary visual cortex
Analysis of visual information for colors and motion
What is the function of the Lateral geniculate body
Thalamic relay of visual information to the primary visual cortex
What is the function of the Primary visual cortex
Discrimination of the shape, size, or texture of objects
What is the function of the Posterior parietal cortex
Specification of movement with visual guidance
What is the function of the Occipitotemporal region
Visual identification of objects
What is the purpose of the vestibulo-ocular reflexes?
The vestibulo-ocular reflexes stabilize visual images during head and body movements.
Relative to head movement, what direction do vestibulo-ocular reflexes move the eyes? Why?
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.
Is nystagmus always a sign of nervous system abnormality?
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.
What is the purpose of smooth pursuit eye movements?
Smooth pursuit eye movements allow gaze to follow a moving object.
What types of eye movement direct gaze?
Saccades, smooth pursuits, and vergence eye movements direct gaze.
Describe Ménière’s disease
Syndrome consisting of both auditory and vestibular disorders associated with abnormal fluid pressures of the inner ear
Describe Dysequilibrium
Loss of balance
Describe Oscillopsia
Loss of visual stabilization
Describe Vertigo
Illusion of motion
Describe Benign paroxysmal positional vertigo
Acute onset of vertigo and nystagmus in response to a rapid change of head position
What is the most common symptom of vestibular dysfunction? A. Nausea and vomiting B. Limb ataxia C. Disequilibrium D. Vertigo E. Upward beat nystagmus
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).
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
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.
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
E: A lesion affecting the right frontal eye fields causes both eyes to deviate ipsilaterally.
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
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.
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
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.
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
E: Lateral head tilt, skew deviation of the eyes, and ocular rotation are all signs of the ocular tilt reaction.
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.
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.
