The Auditory System Flashcards

1
Q

air particles

A

vibrate back and forth

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2
Q

rarefied air vs compressed

A

packets of less dense air vs dense air

creates sound wave

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3
Q

frequency

A

number of compressed or rarefied patches of air that pass ear each second , Hz
peak - rarefied
trough - compressed

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4
Q

intensity

A

air pressure difference between peaks and troughs, dB

small difference = low intensity

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5
Q

range of human hearing

A
20Hz - 20,000Hz
4,000Hz = best frequency
thresholds
high risk e.g. rock connects = 120dB
pain e.g. gun shot = 140dB
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6
Q

anatomy of auditory system

A

outer ear - pinna and tympanic membrane
middle ear - tympanic membrane to oval window - air filled compartment
inner ear - oval window to cochlea and vestibular system

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7
Q

pinna

A

bit you can see

localises sound in vertical plane

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8
Q

tympanic membrane

A

ear drum

vibrates with sound waves - causes movement of ossicles

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9
Q

oval window

A

moves back and forth with ossicles

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10
Q

cochlea and vestibular system

A

cochlea - fluid filled, contains tranducers

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11
Q

ossicles of middle ear

A

malleus - hammer, attached to tympanic membrane
incus - anvil, rigid connection with malleus
stapes - stirrup, flexbile connection with incus, attaches to oval window

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12
Q

how does middle ear transfer sound?

A

middle ear takes large SA sound from tympanic membrane and converts to small SA on oval window - concentrates force of each sound eave

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13
Q

why concentrate sound in middle ear?

A

we live in air filled environment, ear is fluid filled, it is more difficult fo waves to move through fluid so need to concentrate them so no energy is lost as it moves through

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14
Q

if soundwave pushes inwards…..

A

bottom of maleeus moves down

point of incus pushes forward and pushes stapes into oval window = causes fluid movement along cochlea

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15
Q

round window

A

in cochlea

allows fluid to push out, reduces resistance

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16
Q

if sound pulls outwards…..

A

tympanic membrane moves out
malleus moves uo
incus pulls back
pulls stapes out with oval window

17
Q

anatomy of cochlea

A

oval window joins at bottom and causes movement of fluid up to apex
meets helicotrema where fluid moves into different compartemtn back on itself

18
Q

each spiral of cochlea has 3 compartments

A

scala vestibular
scala tymani
scala media

19
Q

scala vestibular

A

fluid intially pushed through from oval window

filled with perilymph - extra cellular fluid

20
Q

scala tympani

A

connects to round window

filled with perilymph

21
Q

scala media

A

filled with endolymph - high K, only found in inner ear, high potential

22
Q

path of fluid in cochlea

A

move up through vestibular - hit helicotrema - move down through tympani

23
Q

organ of corti

A

runs along spiral, from base to apex, contains transducers that sit on basilar membrane

24
Q

basilar membrane

A

runs along coil of cochlea
hair cells sit on top
tectorial membrane sits on top of hair cells

25
hair cells
3 rows of outer hair cells 1 row of inner hair cells all have stereo cilia - move back and forth with fluid movement each haiir cell has 3 rows of cilia in staircase
26
inner hair cell
primary tranducer hair bundles surrounded by endolymph cell body = perilymph
27
anatomy of basilar membrane
different properties depending where it is at basal end - high freq sound smake membrane move more at apex - low feq make membrane move creates tonotopic map basal = stiff, thick, narrow apex = wider and less stiff
28
how does basilar membrane affect hair cells? | if stapes is pulled out....
fluid moves out | membrane pushes upwards, tectorial membrane moves and pushes stereocillia towards tallest one = depolarisation
29
how does basilar membrane affect hair cells? | if stapes moves in....
membrane moves in | hair cells move towards smallest one = hyper polarised = no signal down auditory nerve
30
hair bundles
connected by tip links - pull open channels for transducing broken tip links----> noise induced hearing loss at top of shortest cilia = mechanoelectrical transducer channel pushing towards tallest - opens channel - K moves in
31
if cilia push towards tallest
stretched tip link channels open and K floods in depol of hair cells - moves to base of cell opens voltage gated Ca channel and Ca floods into cell causes exocytosis of glutamate vesicles actiavtes afferent neuron
32
if cilia push towards smallest
``` tip link shortens shuts channel - no K hyperpolarised Ca channels dont open no action potential ```
33
outer hair cells
``` electromotive act as cochlear amplifiers 'dancing hair cells' make inner cell responses bigger - can hear at lower intensities amplify basilar membrane movement ```