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NE3 > phys of auditory system > Flashcards

phys of auditory system Flashcards

1
Q

how is the basilar membrane structured?

A

varied over its length

narrow and stiff near oval and round windows

wider and more flexible near helicotrema

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2
Q

how do high frequency sounds affect basilar membrane?

A

greater deflection where it is narrow

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3
Q

how do low frequency sounds affect basilar membrane?

A

greater deflection where it is loose and flexible

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4
Q

where is frequncy of sound decoded?

A

where there is greatest deflection along membrane

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5
Q

amplitude of sound?

A

sound pressure specifiied by a level

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6
Q

sound?

A

oscillations of air pressure that vary alot

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7
Q

frequency?

A

number of oscillations of pressure per second

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8
Q

how do sound waves propogates through basilar membrane?

A

initiated at basilar membrane, same frequency as sound

goes from base to apex

reaches point of maximal displacement of basilar membrane

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9
Q

what determines how far sound wave propogates through basilar membrane?

A

the flexibility of the membrane

higher frequency sounds max out at base

low frequenc max out at apex

result in tonotopy

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10
Q

what causes stereocilia of outer hair cells to be displaced?

A

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

stereocilia displaced in that plane

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11
Q

how are inner hair cells activated?

A

fluid movement through cochlear duct

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12
Q

how does depolarzation of cell occur?

A

cation channels open at apex of stereocilia

connected to each other via tip links

transmit force to elastic gating spring, opens TRPA1 channels

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13
Q

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

A

mechanotransduction, immediate effects

can respond to stimulus within 50us

dont need receptor potentials

small vibrations such as .3nm can open channel

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14
Q

where is endolymph made and whats its composition?

where is it

A

stria vascularis, but located in membranous labyrinth

bathes apical side of hair cells, in scala media

high in K, similar to ICF

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15
Q

where is perilymph made and whats its composition?

where is it

A

bathes basal end of hair cells

High Na, like ECF

scala vestibuli and tympani

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16
Q

what happens when cation channel open ?

A

bathed in endolumph

causes influx of K, which causes hair cell depolarization

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17
Q

what happens after hair cell is depolarized?

A

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

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18
Q

upward displacemtn of basilar membrane causes what?

A

shearing force that results in lateral displacement of stereocilia

eventually, depolarization of hair cell

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19
Q

where is hair cells located?

A

tips of stereocilia are in tectorial membrane

bodies are on basilar membrane

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20
Q

downward displacemtn of basilar membrane causes what?

A

hyperpolarization of hair cell

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21
Q

what hair cells are responsible for hearing?

A

inner hair cells, most cochlear nerve fibers come from here

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

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22
Q

what maintains electrochemical properties of endolymph?

A

stria vascularis

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23
Q

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

A

cells of stria vascularis extend processes and folds around capillaries

K released from capillaries flows into endolymph

24
Q

what forms BLB and how is it relevant?

A

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

25
Q

how do ototoxic cells disrupt hearing?

A

disrupt function of stria vascularis, diminsh endocochlear potential

26
Q

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

A

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

27
Q

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

A

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

28
Q

what are otoacoustic emissions?

A

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

29
Q

what are otoacoustic emissions used to measure?

A

function of inner and middle ears in infants

30
Q

how do otoacoustic emissions travel?

A

from superior olivary complex

“olicocochlear efferents”

31
Q

what does medial olivary complex innervate?

A

outer hair cells

32
Q

what does lateral olivary complex innervate?

A

inner hair cells

33
Q

what is OAE used to screen for?

A

presence of absence of sound waves generated by cochlear outer hair cells

used to screen for sensorineural hearing loss but not auditory neuropathy

34
Q

how does olivocochlear efferents protect cochlea from extreme sounds?

A

reduce motility of outer hair cells

decrease motion of basilar membreane

reduce responses of inner hair cells and auditory nerve fibers

35
Q

how do middle ear efferents protect cochlea from extreme sounds?

A

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

36
Q

what is implicated in tinnitus?

A

middle ear efferents

37
Q

how do autonomic efferents protect cochlea from extreme sounds?

A

arises from 8th CN

sympathetic adrenergic

regulates vascular tone in clood supply from cochlea

38
Q

what mechanisms protect cochlea from damage?

A

olivocochlear efferents

middle ear efferents

autonomic efferents

39
Q

what does dorsal cochlear nuclei do?

A

integrates acoustic info with somatosensory info

40
Q

what does ventral cochlear nuclei do?

A

processes temporal and spectral features of sound

41
Q

what kind of input do olivary complexes receive?

A

glutamatergic input

42
Q

MSO does what?

A

interaural time differences to help localize sound

43
Q

LSO does what?

A

map of interaural intensity differences to help localize sound

44
Q

what does inferior colliculus do?

A

suppresses echoes, helps with localization

time and intensit differences converge to help find precise origin of sound along horizon

45
Q

what does medial geniculate nucleus do?

A

convergence from spectral and temporal pathways,
process speech inflections

precise info regarding intensity, frequency, binaural properties of sound relayed forward

46
Q

what does primary auditory cortex do?

A

conscious perception of sound

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

47
Q

what does secondary auditory association cortex do?

A

brocas, wernickes, etc

tonotopic map not maintained, unlike others

complex sounds, sound , speech

48
Q

where does sensorineural hearing loss come from?

A

problems in inner ear

with hair cells or cochlear nerve

49
Q

can hair cells regenerate?

A

once damaged, no

50
Q

what does cochlear implant consist of ?

A

internal and external component

receiver that decodes signal and sends signals to electrode array

51
Q

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

A

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

52
Q

what activate anterior semicircular canal?

A

rotation in vertical plane forward

53
Q

what activate horizontal semicircular canal?

A

rotation in horizontal plane

54
Q

what activate utricle?

A

linear acceleration forward and backward

55
Q

what activate saccule?

A

linear acceleration up and down

NE3 (15 decks)

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