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auditory system Flashcards

1
Q

what 3 sections is ear divided into

A

outer, middle and inner ear

each part has specific function

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2
Q

where is ear organ located

A

embedded in petrous portion of temporal bone - hardest bone in body

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3
Q

what are the functions of outer ear/pinna and external acoustic canal(meatus)

A
  • capture sound and focus it on tympanic membrane
  • amplify some frequencies by resonance in canal
  • protect ear from external threats
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4
Q

where does the middle ear begin

A

in tympanic membrane/eardrum

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5
Q

main function of middle ear

A

amplification by focusing vibrations from large to smaller surface area(oval window). change in surface area means pressure is increased.
- using leverage from incus stapes join to increase force on oval window

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6
Q

what are the smallest bones in the body

A

the ossicles: malleus, stapes and incus

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7
Q

what is the hearing part of inner ear

A

cochlear

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8
Q

what is the function of inner ear in hearing

A

transduce vibrations into nerve impulses

- produces a frequency(/pitch) and intensity(/loudness) analysis of sound

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9
Q

what are the 3 compartments contained in cochlea

A

scala vestibuli and scala tympani and scala media

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10
Q

what are the scala vestibuli and scala tympani

A

bone structures which contain perilymph

- high in sodium

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11
Q

what is the scala media

A

membranous structure - contains endolymph (high in potassium)
where hearing organ/ organ of corti is located

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12
Q

what is the basilar membrane

A

structure where organ of corti lies

arranged tonotopically - sensitive to different frequencies at different points along its length

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13
Q

explain the organ of corti

A

contains 1000s of inner and outer hair cells

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14
Q

what is the tectorial membrane

A

located above hair cells and allows their deflection - in turn depolarise the cell
only outer hair cell are in constant contact with tectorial membrane - assist contact with ihc

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15
Q

what is the role of inner hair cells

A 
carry 95% of afferent information of auditory nerve
function = transduction of sound into nerve impulses
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16
Q

what is role of outer hair cells

A 
carry 95% of efferents of auditory nerve
function = modulation of sensitivity of response
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17
Q

why are outer hair cells able to contract

A

have protein in membrane and can change length - makes tectorial membrane closer or away from inner hair cell

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18
Q

what are the hairs on hair cells called

A

stereocilia

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19
Q

explain how transduction occurs

A

deflection of stereocilia towards longest cilium will open k+ channels
ionic interchange depolarises cells
calcium come in via vgcc
neurotransmitter is liberated

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20
Q

what does greater deflection of stereocilia and k+ ion channel opening cause

A

higher amplitudes (louder) sounds

21
Q

what hair cells allow you to hear softer sounds

A

outer hair cells

22
Q

what is the auditory pathway

A

spiral ganglions from each cochlea project -> via audiovestibular nerve to ipsilateral cochlear nuclei (monoaural neurons)
some auditory info crosses at -> superior olive level
after this point all connections are bilateral
-> inferior colliculus
-> medial geniculate body

23
Q

what is frequency/pitch

Hz

A

cycles per second

perceived tone

24
Q

what is amplitude/loudness

dB

A

sound pressure

subjective attribute correlated with physical strength

25
Q

what is the human range of hearing

A

freq - 20 - 20000 Hz

loudness - 0dB to 120dB

26
Q

why is the decibel scale useful

A

range of sensitivity is very large

27
Q

how doe shearing acuity change with age

A

decrease with age, particularly higher frequencies

28
Q

what are the aims of hearing assessmentI

A

is there hearing loss?
what type
of what degree

29
Q

what is a tuning fork used for

A

used to establish probable presence or absence of hearing loss with significant conductive component
- used to provide early and general info and - when audiometry not available

30
Q

what is pure tone audiometry

A

science of measuring hearing acuity in sound intensity and frequency
uses audiometer

31
Q

what is an audiometer

A

device used to produce sound of varying intensity and frequency

32
Q

what is an audiogram

A

graph where hearing thresholds are plotted to define hearing loss or not
normal = 0-20dB

33
Q

what is the central processing assessment

A

assessment of hearing abilities other than detection
e.g sound localisation, filtered speech and speech in noise
uses verbal and non verbal tests

34
Q

what is tympanometry

A

examination used to test condition of middle ear and mobility of eardrum and conduction bones by creating variations of air pressure in air canal

35
Q

what are otoacoustic emissions

A

normal cochlea produces low intensity sounds called OSEs - produced specifically by outer hair cells as they expand and contract
test is often part of newborn hearing screening and hearing loss monitoring

36
Q

what are auditory evoked potentials

A

electrocochleography - electrical activity from cochlea and 8th nerve. evoked by clicks and tone burst
abr - electrical activity from 8th nerve and brainstem nuclei and tracts
late responses - electrical activity from auditory and association cortex

37
Q

what is abr

A

electrical responses from auditory pathway
does not require attention
commonly used in babies and children

38
Q

when would cortical potentials be useful

A

could be affected on neurological conditions or processing problems

39
Q

what is conductive hearing loss

A

problem is located in outer or middle ear

40
Q

what is sensorineural loss

A

problem in inner ear or auditory nerve

41
Q

what is mixed hearing loss

A

conduction and transduction of sound are affected

42
Q

what does degree of hearing loss depend on

A

hearing thresholds

43
Q

what are some causes of conductive hearing loss

A

wax
foreign body
otitis
otosclerosis

44
Q

what are some causes of sensorineural loss

A

presbycusis - loss with age of hair cells
ototoxicity
8th nerve tumour

45
Q

treatment for hearing loss

A

treat underlying cause
hearing aids
cochlear implants
brainstem implants

46
Q

what do hearing aids do

A

amplify sounds

47
Q

how do cochlear implants work

A

replaces function of hair cells by receiving sound analysing it, transforming into electrical signals and sending an electric impulse directly to auditory nerve
needs functional auditory nerve to function*

48
Q

how do brainstem implants work

A

electrical signals can be sent to set of electrodes placed in brainstem
very risky - advised only for bilateral auditory nerve damage

brs2 (65 decks)

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