Physiology Of Auditory System

Question 1

Which part of basilar membrane conveys which pitch?

Answer 1

Near oval window is narrow and stiff for High pitch, while near oval and round window it is wide and more flexible for lower frequency

Question 2

How does sound propagate moving outer hair cells?

Answer 2

Vibration of basilar membrane creates pressure differential

-this results in shearing force against tectorial membrane moving outer hair cells

Question 3

Overview of Depolarization of Hair Cells

Answer 3

Deploarization occurs when K+ channels open at apex of stereocilia; this causes depolarization bringing Ca2+
-stereocilia connected via tip links which transmit forces and opens TRPA1 channels
—Very rapid opening and are very sensitive

Question 4

Endolymph vs Perilymph

Answer 4

Endolymph is like intracellular fluid
-high K, low Na

Perilymph has high Na, low K

Question 5

How are hair cells hyperpolarized?

Answer 5

Downward displacement of basilar membrane

Question 6

What is the action of stria vascularis? Also, how will drugs that affect blood labyrinth barrier affect hearing?

Answer 6

Creates the K+ rich endolymph that surrounds hair cells.

Endocochlear potential is maintained by stria vascularis, and forms the BLB
—drugs that affect this, will affect the impact of hearing

Question 7

Olivocochlear efferents

Answer 7

Reduce electricomotility of outer hair cells

Decrease basilar membrane motion

Reduce responses of inner hair cells and auditory nerve fibers

Question 8

Medial Ear Efferents

Answer 8

Tensor tympani and stapedius
-attenuate sound

Bilateral response to high sound levels

Contractions decrease transmission of sound

Act at low frequencies and may prevent damage

Question 9

Autonomic efferents

Answer 9

Arises from CN VIII

-sym adrenergic fibers that regulate vascular tone in blood to cochlea

Question 10

Dorsal and ventral cochlear Nuclei

Answer 10

Dorsal CN-integrates accoustic info w somatosensory info

Ventral CN-begins processing the temporal and spectral features of sound

Question 11

MSO and LSO

Answer 11

MSO generates a map of interaural time differences to help localize sound

LSO generates map of intensity to help localize source of sound

Question 12

Inferior Colliculus and hearing

Answer 12

Suppresses echos, and helps arrive at final estimation of localization of sound

Question 13

Medial Geniculate Nucleus and Hearing

Answer 13

Precise info regarding intensity, frequency, and binaural properties of sound integrated and relayed outward

Question 14

Primary Auditory Cortex FXN

Answer 14

Essential in conscious perception of sound and higher order processing

Question 15

Secondary Auditory Association Cortex (A2) fxn

Answer 15

Respond to more complex sounds, identifying sounds and speech

Question 16

Sensorineural hearing loss vs Conductive

Answer 16

Sensorineural is due to damage of CN VIII or the hair cells

Conductive is due to the ossicles of the ear itself
-can be treated with cochlear implant

Question 17

Utricle detects…

Answer 17

Linear acceleration forward and backward

Question 18

Which part of ear detects linear acceleration up and down?

Answer 18

Saccule

You suck up

Question 19

Let’s say you do a somersault.. which part of ear detects the rotation?

Answer 19

Anterior semicircular canal

Question 20

Let’s say you spin around like a ballerina.. which part of ear detects motion?

Answer 20

Horizontal semicircular canal