Lecture 12 - Vestibular System - Peripheral Transduction and Central Pathways

Question 1

What are the two labyrinths in the inner ear that contain the five vestibular organs (two otolith organs and three semicircular canals) of the inner ear?

Answer 1

bony labyrinth
membranous labyrinth

Question 1

What does the bony labyrinth do?

Answer 1

-it is part of the temporal bond and it contains perilymph fluid and the perilymph fluid suspends the membranous labyrinth
-has the three semicircular canals

Question 2

What does the membranous labyrinth do?

Answer 2

-within the bony labyrinth and contains the endolymph fluid which is potassium rich
-has the two otolith organs the utricle and saccule

Question 3

What are the two otolith organs and what do they do?

Answer 3

-utricle and saccule
-detect horizontal and vertical movement of the head and body

Question 4

What type of movement does the utricle detect?

Answer 4

detects horizontal movement of the head and body

Question 5

What type of movement does the saccule detect?

Answer 5

detects vertical movement of the head and body

Question 6

What are otoconia and where are they located?

Answer 6

ear crystals that are layers on top of the otolithic membrane and their added and and movement drags the otolithic membrane which in tuns bends the stereocilia of the hair cells

Question 7

What are the semicircular canals how many are there and what do they do?

Answer 7

-there are three and are oriented 90 degrees to each other and detect rotation in three directions

Question 8

What are the three directions of rotation the three semicircular canals detect?

Answer 8

roll - x-axis rotation - nodding your head side to side
pitch - y-axis rotation - nodding you head yes
yaw- z-axis rotation - nodding your hear no

Question 9

What is located within each semicircular canal?

Answer 9

ampulla - a swelling

Question 10

What is located within each ampulla?

Answer 10

-crista ampullaris which contains cupula

Question 11

What does movement of the endolymph fluid cause to move in the semicircular canals?

Answer 11

within the ampulla there is the crista ampullaris which contains the cupula which is what moves and bends the stereocilia of hair cells

Question 12

What is a type 1 hair cell?

Answer 12

more modern in their evolution and they have a kinocilium that modulates the sensitivity of the cell and the afferent ending which is the calyx ending which is cup shaped

Question 13

What is a type 2 hair cell?

Answer 13

evolutionarily older has a kinocilium and many stereocilia

Question 14

`What are the steps in vestibular transduction?

Answer 14

1. movement of the endolymph fluid in the membranous labyrinth in repsone to head and body movements causes the otolithic membrane in the utricile and saccule and the cupula in the semicircular canals to move
2. the stereocilia and kinocilium bend which opens the tension gated K+ channels which cause depolarization
3. influx of potassium causes release of neurotransmitters to stimulate the vestibular nerve

Question 15

What is the key difference between auditory and vestibular transduction?

Answer 15

-the direction of the fluid matters because in the vestibular the direction can cause the channels to open or close while in auditory any sort of movement of the fluid will cause the channels to open

Question 16

What is the overview of the central vestibular pathway?

Answer 16

vestibular nerve —> vestibular nuclei in medulla and pons —-> cranial nerve nuclei for CN III, IV, and VI which is the oculomotor nerve , trochlear nerve, and abducens nerve and this coordinate eye movement with balance

Question 17

What are the two descending vestibulospinal tracts and what do they do?

Answer 17

-communicate with muscles in the periphery to maintain balance
-medial vestibulospinal tract
- controls the medial muscle and the intercostals
-lateral vestibulospinal tract
- controls the lateral muscles in the arms and legs

Question 18

What is the vestibulocerebellar circuitry?

Answer 18

vestibular nerve —-> vestiubular nucleus —–> flocculonodular lobe/vermis —–> fastigial nucleus —–> gaze centers, vestibular nucelus, reticular nucleus

fastigial nucleus coordinate eye movements and motor movement for balance

Question 19

What is vertigo?

Answer 19

characterized by dizziness and nausea due to irritation of the vestibular nerve

Question 20

What is Meniere’s Disease?

Answer 20

rare disease caused by buildup of endolymph fluid which leads to swelling in the vestibular and cochlear structures
-causing vertigo and tinnitus