FE: Lecture 4: Vestibular Part 2

Question 1

Where are the vestibular hair cells located?

Answer 1

in the utricle macula, saccule macula and ampullary crests

Question 2

How does hair move in the organs?

Answer 2

depolarized by force in direction of the arrows, however in the ampulla the hairs are unidirectional

Question 3

What is the path of the AP from hair to end?

Answer 3

1. synapse from hair to primary afferent fibers
2. fibers go to scarpa’s ganglia then synapse in ipsilateral vestibular nuclei
3. ampullary crest goes to medial and superior nuclei- detects head rotation (angular acceleration)
4. maccula of utricle and saccule go to lateral nucleus (tilt and linear acceleration)

Question 4

Where are the vestibular nuclei?

Answer 4

1. inferior and medial nuclei in the medulla

2. medial, superior and lateral are in the pons

Question 5

What is another name for the vestibular hair cells?

Answer 5

crista ampullaris- hair cells have same orientation

Question 6

What is function of the cupulla in the ampulla?

Answer 6

this amplifies the force of the flow of endolymph

Question 7

How is the movement of endolymph initiated?

Answer 7

any time you rotate your head the endolymph will move, this will either bend the stereocilia towards or away from the kinocilia

Question 8

In regards to hyper and depolarization what rotations are needed for each?

Answer 8

ipsilateral rotation- depolarizes

contralateral- hyperpolarizes

Question 9

If your turn your head to the left what happens in the ampulla?

Answer 9

left ampulla turns left and endolymph goes to the right which depolarizes the left side

Question 10

What happens for in order for the Vestibular- Ocular reflex (VOR) or Doll’s eye reflex?

Answer 10

after synapsing at the vestibular nuclei the AP travels of the MLF this excites the contralateral abducens nerve and ipsilateral Oculomotor nucleus which then sends LMN to those muscles

Question 11

Therefore what happens when your turn your head to the right?

Answer 11

right vestibular nuclei activated due to flow of endolymph flowing toward kinocilia

this activates Left eye ABD, Right eye ADD

Question 12

How many degrees does a normal VOR usually work?

Answer 12

15 degrees then eyes jump back to center

Question 13

What is movements behind nystagmus?

Answer 13

slow then fast eye movements

slow drift opposite of head rotation then jump back in same rotation

Question 14

What is the functional anatomy behind nystagmus?

Answer 14

slow phase- vestibular nuclei

quick phase- pontine reticular nuclei

Question 15

What is abnormal nystagmus?

Answer 15

head is fixed but constant nystagmus

due to vestibular lesion