Flashcards in FE: Lecture 4: Vestibular Part 2 Deck (15):
Where are the vestibular hair cells located?
in the utricle macula, saccule macula and ampullary crests
How does hair move in the organs?
depolarized by force in direction of the arrows, however in the ampulla the hairs are unidirectional
What is the path of the AP from hair to end?
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)
Where are the vestibular nuclei?
1. inferior and medial nuclei in the medulla
2. medial, superior and lateral are in the pons
What is another name for the vestibular hair cells?
crista ampullaris- hair cells have same orientation
What is function of the cupulla in the ampulla?
this amplifies the force of the flow of endolymph
How is the movement of endolymph initiated?
any time you rotate your head the endolymph will move, this will either bend the stereocilia towards or away from the kinocilia
In regards to hyper and depolarization what rotations are needed for each?
ipsilateral rotation- depolarizes
If your turn your head to the left what happens in the ampulla?
left ampulla turns left and endolymph goes to the right which depolarizes the left side
What happens for in order for the Vestibular- Ocular reflex (VOR) or Doll's eye reflex?
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
Therefore what happens when your turn your head to the right?
right vestibular nuclei activated due to flow of endolymph flowing toward kinocilia
this activates Left eye ABD, Right eye ADD
How many degrees does a normal VOR usually work?
15 degrees then eyes jump back to center
What is movements behind nystagmus?
slow then fast eye movements
slow drift opposite of head rotation then jump back in same rotation
What is the functional anatomy behind nystagmus?
slow phase- vestibular nuclei
quick phase- pontine reticular nuclei