Exam 3 (Chapter 18) - Vestibular System

Question 1

The macula is part of the ________.

Answer 1

Utricle and saccule

Question 2

What is the membranous labyrinth of the vestibular organ filled with?

Answer 2

Endolymph

Question 3

The crista ampullaris responds directly to motion of _________.

Answer 3

Endolymph

Question 4

What is the gelatinous substance that extends across the ampulla and interrupts each semicircular duct?

Answer 4

Cupula

Question 5

The crista ampullaris is part of the ________.

Answer 5

Semicircular duct

Question 6

Neurons in the vestibular nerve are classified as _________. They are located in the ___________.

Answer 6

Bipolar neurons; vestibular ganglion

Question 7

What do the utricle and saccule detect?

Answer 7

Linear acceleration and deceleration

Question 8

What is the semicircular duct that lies horizontally when the head is in normal position and detects rotations around the vertical axis?

Answer 8

Lateral semicircular duct

Question 9

Potential change produced in hair cells of the vestibular receptors is _________.

Answer 9

Graded potential

Question 10

Which cranial nerves are under the control of the medial longitudinal fasciculus?

Answer 10

Oculomotor (III)
Trochlear (IV)
Abducent (VI)

Question 11

A lesion involving the right vestibulospinal tract is likely to cause _________.

Answer 11

Body fall to the right

Question 12

The vestibulospinal tract originates from the _________. It excites ___________ neurons for extensor muscles.

Answer 12

Vestibular nuclei; lower motor

Question 13

The pyramid contains fibers of the _______.

Answer 13

Corticospinal tract

Question 14

What is true about the vestibular system?

Answer 14

Bending stereo cilia of sensory cells toward the kinocilium excite the vestibular nerve fibers.

Question 15

What happens when the head starts to rotate counterclockwise in a horizontal direction?

Answer 15

The left vestibular nerve increases the firing rate and the direction of nystagmus is to the left.

Question 16

Where does the medial longitudinal fasciculus originate from?

Answer 16

Vestibular nuclei

Question 17

The vestibulospinal tract descends to the spinal cord and _________ lower motor neurons innervating the ________ muscles.

Answer 17

Stimulates; extensors

Question 18

A dog shows nystagmus to the left, but cerebellar function appears normal, suggesting a lesion of the __________.

Answer 18

Right vestibular nuclei

Question 19

A lesion of the right vestibular nerve causes the body to fall to which side?

Answer 19

Right

Question 20

A lesion involving the left caudal cerebellar peduncle is likely to cause what?

Answer 20

Body fall to the right

Question 21

A mass of meningioma compressing only the left caudal cerebellar peduncle is likely to induce what?

Answer 21

Nystagmus to the left

Question 22

A dog shows the following clinical signs:
- Nystagmus to the left
- Walking/drifting to right

The lesion most likely involves _______.

Answer 22

Right vestibular nerve

Question 23

A lesion of the flocculonodular lobe can produce paradoxical vestibular syndrome. What is the basis for this?

Answer 23

The net effect of the cerebellum on the vestibular system is inhibitory. When there is a cerebellar lesion, there is more excitation of the affected vestibular nucleus.