phys of auditory system

Question 1

how is the basilar membrane structured?

Answer 1

varied over its length

narrow and stiff near oval and round windows

wider and more flexible near helicotrema

Question 2

how do high frequency sounds affect basilar membrane?

Answer 2

greater deflection where it is narrow

Question 3

how do low frequency sounds affect basilar membrane?

Answer 3

greater deflection where it is loose and flexible

Question 4

where is frequncy of sound decoded?

Answer 4

where there is greatest deflection along membrane

Question 5

amplitude of sound?

Answer 5

sound pressure specifiied by a level

Question 6

sound?

Answer 6

oscillations of air pressure that vary alot

Question 7

frequency?

Answer 7

number of oscillations of pressure per second

Question 8

how do sound waves propogates through basilar membrane?

Answer 8

initiated at basilar membrane, same frequency as sound

goes from base to apex

reaches point of maximal displacement of basilar membrane

Question 9

what determines how far sound wave propogates through basilar membrane?

Answer 9

the flexibility of the membrane

higher frequency sounds max out at base

low frequenc max out at apex

result in tonotopy

Question 10

what causes stereocilia of outer hair cells to be displaced?

Answer 10

pressure differential by vibration of basilar membrane
results in shearing force against stationary tectorial membrane

stereocilia displaced in that plane

Question 11

how are inner hair cells activated?

Answer 11

fluid movement through cochlear duct

Question 12

how does depolarzation of cell occur?

Answer 12

cation channels open at apex of stereocilia

connected to each other via tip links

transmit force to elastic gating spring, opens TRPA1 channels

Question 13

what kind of channels are TRPA1? whats so special about them?

Answer 13

mechanotransduction, immediate effects

can respond to stimulus within 50us

dont need receptor potentials

small vibrations such as .3nm can open channel

Question 14

where is endolymph made and whats its composition?

where is it

Answer 14

stria vascularis, but located in membranous labyrinth

bathes apical side of hair cells, in scala media

high in K, similar to ICF

Question 15

where is perilymph made and whats its composition?

where is it

Answer 15

bathes basal end of hair cells

High Na, like ECF

scala vestibuli and tympani

Question 16

what happens when cation channel open ?

Answer 16

bathed in endolumph

causes influx of K, which causes hair cell depolarization

Question 17

what happens after hair cell is depolarized?

Answer 17

Ca channels at base of cells open

NT vesicules fuse to basilar membrane, release glutamate into cleft

afferent nerve fibers are stimulated, transmit signal to CNS

Question 18

upward displacemtn of basilar membrane causes what?

Answer 18

shearing force that results in lateral displacement of stereocilia

eventually, depolarization of hair cell

Question 19

where is hair cells located?

Answer 19

tips of stereocilia are in tectorial membrane

bodies are on basilar membrane

Question 20

downward displacemtn of basilar membrane causes what?

Answer 20

hyperpolarization of hair cell

Question 21

what hair cells are responsible for hearing?

Answer 21

inner hair cells, most cochlear nerve fibers come from here

outer hair cells amplify signals that are read by inner hair cells

Question 22

what maintains electrochemical properties of endolymph?

Answer 22

stria vascularis

Question 23

howis intraepithelial plexus formed? how does it allow endolymph to have high ?

Answer 23

cells of stria vascularis extend processes and folds around capillaries

K released from capillaries flows into endolymph

Question 24

what forms BLB and how is it relevant?

Answer 24

endocochlear potential which drives positively charged ions into hair cells

maintained bystria vascularis

one of the main sites of drug entry to access inner hair cell

Question 25

how do ototoxic cells disrupt hearing?

Answer 25

disrupt function of stria vascularis, diminsh endocochlear potential

Question 26

What are inner hair cells, how are they organized, what do they do?

Answer 26

primary source of auditory info arranged in a single layer synapse with peripheral terminal of primary afferent sensory neuron modulated by efferent neuron as well

Question 27

What are outer hair cells, how are they organized, what do they do?

Answer 27

amplify sound waves, moving basilar membrane specialied type of epithelial cell contractile, boost vibration of membrane , amplify three rows synapse with sensory afferent from spiral ganglion and terminals from efferent neurons

Question 28

what are otoacoustic emissions?

Answer 28

retrograde movement through oval window and through ossicles to cause tympanic memebrane to move

Question 29

what are otoacoustic emissions used to measure?

Answer 29

function of inner and middle ears in infants

Question 30

how do otoacoustic emissions travel?

Answer 30

from superior olivary complex "olicocochlear efferents"

Question 31

what does medial olivary complex innervate?

Answer 31

outer hair cells

Question 32

what does lateral olivary complex innervate?

Answer 32

inner hair cells

Question 33

what is OAE used to screen for?

Answer 33

presence of absence of sound waves generated by cochlear outer hair cells used to screen for sensorineural hearing loss but not auditory neuropathy

Question 34

how does olivocochlear efferents protect cochlea from extreme sounds?

Answer 34

reduce motility of outer hair cells decrease motion of basilar membreane reduce responses of inner hair cells and auditory nerve fibers

Question 35

how do middle ear efferents protect cochlea from extreme sounds?

Answer 35

tensor tympani atenuates sound stapedius attenuates sound bilateral response to high sound contraction decrease transmission of sound act at low frequencies, prevent low frequency masking may prevent damage, protect hair cells

Question 36

what is implicated in tinnitus?

Answer 36

middle ear efferents

Question 37

how do autonomic efferents protect cochlea from extreme sounds?

Answer 37

arises from 8th CN sympathetic adrenergic regulates vascular tone in clood supply from cochlea

Question 38

what mechanisms protect cochlea from damage?

Answer 38

olivocochlear efferents middle ear efferents autonomic efferents

Question 39

what does dorsal cochlear nuclei do?

Answer 39

integrates acoustic info with somatosensory info

Question 40

what does ventral cochlear nuclei do?

Answer 40

processes temporal and spectral features of sound

Question 41

what kind of input do olivary complexes receive?

Answer 41

glutamatergic input

Question 42

MSO does what?

Answer 42

interaural time differences to help localize sound

Question 43

LSO does what?

Answer 43

map of interaural intensity differences to help localize sound

Question 44

what does inferior colliculus do?

Answer 44

suppresses echoes, helps with localization time and intensit differences converge to help find precise origin of sound along horizon

Question 45

what does medial geniculate nucleus do?

Answer 45

convergence from spectral and temporal pathways, process speech inflections precise info regarding intensity, frequency, binaural properties of sound relayed forward

Question 46

what does primary auditory cortex do?

Answer 46

conscious perception of sound higher order processing of sound (loudness, volume changes, frequency changes)

Question 47

what does secondary auditory association cortex do?

Answer 47

brocas, wernickes, etc tonotopic map not maintained, unlike others complex sounds, sound , speech

Question 48

where does sensorineural hearing loss come from?

Answer 48

problems in inner ear with hair cells or cochlear nerve

Question 49

can hair cells regenerate?

Answer 49

once damaged, no

Question 50

what does cochlear implant consist of ?

Answer 50

internal and external component receiver that decodes signal and sends signals to electrode array

Question 51

where is electrode array from impant inserted into, what does that do?

Answer 51

cochlea through oval window sits on cochlear duct along CN VIII afferents electric signals along electrode stimulate a particular cochlear nerve along basilar membrane array mimics tonotopy, stimulate nerves at discrete frequencies

Question 52

what activate anterior semicircular canal?

Answer 52

rotation in vertical plane forward

Question 53

what activate horizontal semicircular canal?

Answer 53

rotation in horizontal plane

Question 54

what activate utricle?

Answer 54

linear acceleration forward and backward

Question 55

what activate saccule?

Answer 55

linear acceleration up and down