Vestibular System

Question 1

what is the vestibular labyrinth?

Answer 1

an outer boney labyrinth filled with perilymph (ionicly similar to CSF)
inner endolymph with positive ions, K+

Question 2

what is in the inner membranous layer?

Answer 2

–utricle and saccule- detect inner ear acceleration and static head tilt
–ampullae- detect angular acceleration

Question 3

what do vestibular hair cells do?

Answer 3

transduce head motion into neuronal activity
Synapse with neurons from vestibular ganglion

Question 4

What is the protein that attaches the sterocillia together called?

Answer 4

Tip links

Question 5

What happens when vestibular hair cells bend toward the kinocilium

Answer 5

When stereocilia bend towards the kinocilium, tip links stretch, opening the chain of channels and allowing ions
to enter the cell
 Influx of K+ ions from the endolymph leads to depolarization of the cell and release of neurotransmitter, which stimulates the vestibular afferent

Question 6

What happens when the stereocillia bend away from the kinocioium

Answer 6

Relaxes tip links encourage ion channel closure
Hyperpolerization of cell

Question 7

What does it mean that vestibular hair cells are tonically active?

Answer 7

Vestibular neurons receive constant baseline stimulation

Question 8

What is the relation of K and hair cells?

Answer 8

At rest, a small amount of K+ leaks into vestibular hair cells, driven by negative membrane
potential and high apical K+ in the endolymph

Question 9

What Do the Utricle and Saccule Detect?

Answer 9

Linear acceleration – movement in a straight line
 Static head tilt (effects on receptive elements mimic linear acceleration)

For example, if you do the following without tilting your
head:
 Walk forward (straight line on x axis)
 Step to the side (straight line on y axis)
 Squat (straight line on z axis)

Question 10

The utricle is specialized to detect … movements

Answer 10

horizontal like walking forward, side stepping, riding in car

Question 11

The saccule is specialized to detect:

Answer 11

Vertical movement like squatting or riding in an elevator

Question 12

Can utricle and saccule defect acceleration or deceleration

Answer 12

Both

Question 13

Linear acceleration is detected by the ……., a
structure within the utricle or saccule

Answer 13

macula

Question 14

The macula contains a layer of cells that include
hair cells. Stereocilia of hair cells extend into a
gelatinous matrix called the …..

Answer 14

otolithic membrane

Question 15

Embedded in the otolithic membrane are CaCO2
crystals called

Answer 15

otoliths
—Otoliths are three times as dense as surrounding
structures