Vestibular Ocular Reflex (M1)

Question 1

What eye movements account compensate for relatively brief, transient head rotations and translations (walking)?

Answer 1

vestibular eye movements (vestibular ocular reflex, VOR)

Question 2

When the head turns to the right, which horizontal canal is inhibited? 1. What are the yoked ocular muscles that are inhibited? 2

Answer 2

1. left horizontal canal

2. right lateral rectus and left medial rectus

Question 3

What motions do the horizontal canals detect? 1. Does the canal depolarize or hyperpolarize when the head is rotated in the direction of the canal? 2

Answer 3

1. horizontal rotations

2. depolarizes

Question 4

What is the gelatinous body that contains the cilia from the hair cells that make up the crista? 1. What is this responsible for? 2

Answer 4

1. the cupula

2. bows with the flow of endolymph and generates a directional response of the crista (either excitatory or inhibitory)

Question 5

Which ocular muscles are linked to the anterior vertical canals?

Answer 5

1. ipsilateral recti

2. contralateral obliques

Question 6

When the anterior vertical canals are stimulated, what are the yoked muscles that are stimulated?

Answer 6

1. ipsilateral superior rectus

2. contralateral inferior oblique

Question 7

What are the mechanisms of the interaction between the stereocilia and the kinocilium?

Answer 7

1. bending of stereocilia towards kinocilium depolarizes the hair cell, increasing the firing of the nerve fiber
2. bending of stereocilia away from the kinocilium hyperpolarizes the hair cell, decreasing the firing of the nerve fiber

Question 8

How are the semicircular canals arranged relative to each other?

Answer 8

orthogonally (90deg to each other)

Question 9

What are found at the top of the each hair cell that make up the crista within the ampulla?

Answer 9

1. multiple stereo cilia of variable length

2. a single kinocilium at one edge

Question 10

Which vertical canal is inhibited when the head is rotated to the left and then forward (down)? 1. What ocular muscles and inhibited? 2

Answer 10

1. left posterior canal

2. right inferior rectus and left superior oblique

Question 11

Which canals are stimulated when the head is tilted backward (up)? 1. Inhibited? 2

Answer 11

1. posterior canals

2. anterior canals

Question 12

What is the vestibular apparatus adjacent to and continuous with? 1. What is it filled with? 2

Answer 12

1. cochlea in inner ear

2. viscous endolymph

Question 13

For the horizontal canals, is the cupula deflected towards or away from the utricle when it is stimulated?

Answer 13

towards

Question 14

When the head turns to the right, which horizontal canal is stimulated? 1. What are the yoked ocular muscles that are stimulated? 2

Answer 14

1. right horizontal canal

2. right medial rectus and left lateral rectus

Question 15

Which canals are stimulated when the head is tilted forward (down)? 1. Inhibited? 2

Answer 15

1. anterior canals

2. posterior canals

Question 16

Within the ampulla of the semicircular canals, what detects the flow and is a collection of sensory hair cells?

Answer 16

crista (ampularis)

Question 17

For the vertical canals, is the cupula deflected towards or away from the utricle when it is stimulated?

Answer 17

away from

Question 18

What portion of the vestibular apparatus detects linear acceleration (often gravity)?

Answer 18

otolith

Question 19

What portion of the vestibular apparatus detects rotational acceleration?

Answer 19

the 3 semicircular canals

Question 20

What is the latency for rotational VOR? 1. Is this considered fast or slow? 2

Answer 20

1. 16ms

2. very fast

Question 21

When the posterior vertical canals are stimulated, what are the yoked muscles that are stimulated?

Answer 21

1. ipsilateral superior oblique

2. contralateral inferior rectus

Question 22

What is the flow of the endolymph inside of the canals relative to the direction of head rotation? 1. What is it detected by? 2

Answer 22

1. opposite

2. ampulla

Question 23

What are the names of the three semicircular canals?

Answer 23

1. lateral (horizontal)
2. anterior vertical
3. posterior vertical

Question 24

Which ocular muscles are linked to the posterior vertical canals?

Answer 24

1. ipsilateral obliques

2. contralateral recti

Question 25

Which ocular muscles are almost purely vertical acting when the head is rotated to the left?

Answer 25

1. the right recti muscles

2. left obliques

Question 26

Which way do the eyes move relative to the head for VOR movements?

Answer 26

opposite to head movement

Question 27

Which vertical canal is stimulated when the head is rotated to the left and then forward (down)? 1. What ocular muscles and stimulated? 2

Answer 27

1. right anterior canal

2. right superior rectus and left inferior oblique