Efferent and Vestibular Systems

Question 1

What are the two main divisions of the efferent system? Which one do we know more about?

Answer 1

Caudal efferent system and Rostral efferent system

Know more about Caudal

Question 2

What are the 3 main feedback loops in the rostral portion? Which is the main auditory processing loop?

Answer 2

Reciprocal Loop 1-AC/IC/MGB (main auditory processing loop)

Reciprocal loop 2-AC/IC/PTG, Reciprocal loop 3-AC/SC/MGB

Question 3

The neurons in the lateral olivocochlear bundle originate from where?

Do they mostly have crossed or uncrossed projections?

Answer 3

Originate from LSO and surrounding area

Most uncrossed

Question 4

The neurons in the medial olivocochlear bundle originate from where? Do they mostly have crossed or uncrossed projections?

Answer 4

Arise from MNTB VNTB, DMPO, VMPO

Most crossed

Question 5

Describe the connections of MOCB fibers to IHCs and OHCs.

Answer 5

Connect directly to OHCs and indirectly to IHCs (attach to afferent fibers)

Question 6

How do rate-intensity functions change with background noise? Noise + MOCB?

Answer 6

Without noise, a standard sigmoidal relationship is seen between tone intensity and firing rate, and the MOCB stimulation shifts the function by 12 dB along intensity access. With noise added, the function becomes much flatter, and the MOCB stimulation reverses the effects and steepens the function to some extent (intensity no longer shifted).

Question 7

What is the average change in threshold for an ANF with MOCB stimulation?

Answer 7

15 dB reduction

Question 8

How does the cochlear microphonic change with MOCB stimulation?

Answer 8

CM is increased at low and mid frequencies

Question 9

How does the compound action potential change with MOCB stimulation?

Answer 9

Suppressed

Question 10

How does the summating potential change with MOCB stimulation?

Answer 10

Suppressed

Question 11

How does the endocochlear potential change with MOCB stimulation?

Answer 11

Reduced by 6-7%

Question 12

How does MOCB stimulation change hair cell polarization?

Answer 12

Causes hair cell hyperpolarization (less excitatory)

Question 13

What is the end organ of sensation for the vestibular system?

Answer 13

Cristae

Question 14

How many semicircular canals are there?

Answer 14

3

Question 15

Which areas are able to determine linear motion? Angular motion?

Answer 15

Saccule and utricle is for linear motion

Semicircular canals for angular motion

Question 16

What is the typical spontaneous rate of vestibular hair cells?

Answer 16

90 spikes/sec

Question 17

What is the cupula? What does it do?

Answer 17

Gelatinous mass
The rotation of the head causes fluid to lag behind the rotation of the canal walls. Because the fluid is “blocked” by the cupula, the pressure difference causes the cupula to move, thus bending the stereocilia

Question 18

If a head rotates and accelerates to the left, how do the left and right vestibular afferent fibers respond?

Answer 18

One side excitation, other side causes inhibition

L: increase in firing rate, R: inhibition