efferent pathways

Question 1

efferent

Answer 1

away from a central organ or part

Question 2

what do efferent nerves carry

Answer 2

will carry motor impulses away from CNS

Question 3

two sections of the pathway

Answer 3

rostral and olivocochlear bundle

Question 4

rostral division

Answer 4

originates in the auditory cortex
-descends to the MGB and midbrain region
-efferent fibers at MGB and IC may give rise to additional fibers
-physiology/function of these is not well understood

Question 5

olivocochlear bundle (OCB)

Answer 5

caudal efferent system
-lateral and medial divison
-exert control over synaptic transmission
-mainly an inhibitory role

Question 6

lateral OCB

Answer 6

originates from cells near the lateral superior olive
-mostly uncrossed
-unmyelinated
-fibers terminating on dendrites beneath the IHC

Question 7

medial OCB

Answer 7

originates near the medial superior olive
-mainly crossed fibers to contralateral cochlea
-myelinated

Question 8

what do it mean to be a crossed OCB?

Answer 8

crosses the tunnel of corti and space of nuclei within the cochlea
-connects directly to OHC
-within MOCB, crosses to contralateral cochlea (so MSO to opposite cochlea)

Question 9

how is a OCB (olivocochlear bundle) shown?

Answer 9

(olivocochlear bundle) its an electrical stimulation of the OCB fibers while making measurements such as ABR, OAE, and tuning curves

Question 10

tuning curves with OCB

Answer 10

stimulation of an OCB will cause a less sharp curve

Question 11

why do we have an efferent system?

Answer 11

for hearing in noise : studies have shown that the medial OCB can trigger OHC motility
-this enhances the BM movement
-helps release from masking

Question 12

efferent vestibular connections

Answer 12

projections to the hair cells
-originating in the reticular formation (lateral to abducens nucleus)
-goes bilaterally to vestibular division of CN 8
-terminating directly or indirectly