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PBL SEM 3 > 4 - hearing — how we do it and how it goes wrong lecture > Flashcards

4 - hearing — how we do it and how it goes wrong lecture Flashcards

1
Q

at what dB roughly is conversation?

A

60/70dB

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2
Q

below what dB is hearing damage negligible?

A

75dB

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3
Q

what is the measurement for frequency?

A

Hz

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4
Q

what is the normal hearing range?

A

20-20000Hz

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5
Q

what is the hearing range in Hz for speech?

A

200-500 Hz

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6
Q

noise damage is cumulative — explain

A
  • longer exposure + louder noise = more damage
  • hearing deteriorates as we get older
  • happens preferentially in the high frequencies

it is possible to guess someone’s age depending on what Hz they can hear

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7
Q

by how much does the external ear (pinna) magnify sound by?

A

about 15dB

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8
Q

what is an advantage of the asymmetric shape of the pinna?

A

the curls of the pinna modulate sound to allow you to tell if someone is behind or in front of you

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9
Q

how can the external ear reduce hearing?

A

can collect debris and moisture — encourage bacterial growth — reduces hearing

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10
Q

describe the ear canal skin

A
  • migrates
  • grows in one direction without flaking off
  • debris slowly moves outwards
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11
Q

what are the 2 types of wax and in who are they most common?

A
  • “honey wax” — africans and caucasians
  • “flaky wax” — asians
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12
Q

what is the universal quality of wax?

A

WATERPROOF — wax stops water from hanging around and reducing our hearing

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13
Q

why does the eardrum require air on both sides?

A

to be able to vibrate with the sound pressure waves

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14
Q

what is the function of the eustachian tube?

A

lets air in in emergencies to prevent eardrum from bursting due to abnormal pressures

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15
Q

decibel increments?

A

logarithmic

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16
Q

in water, there is a lot more energy, therefore _____ displacement of the _____ window occurs to transmit the sound

A

lower displacement

oval window

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17
Q

what part of the ossicles is embedded in the tympanic membrane? what is the function?

A

handle of malleus — starts vibration of the ossicles

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18
Q

where is the vibration of the ossicles transferred to?

A

oval window

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19
Q

what is the transmission peak across the middle ear?

A

1kHz = in range of our speech reception

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20
Q

what is the centre of speech frequency we use to communicate with each other?

A

peak frequency = 2 kHz

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21
Q

what are the 2 muscles in the middle ear?

A

stapedius and tensor tympani

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22
Q

what is the function of stapedius and tensor tympani?

A

stiffen the ossicles — make us deafer — protect inner ear from noise damage

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23
Q

how long can the 2 muscels of the middle ear work before needing time to relax?

A

40 mins

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24
Q

functions of the middle ear?

A
  • tympanic membrane/stimulus coupling — large TM to catch energy — focus on to small oval window — use ossicles to transmit vibration energy
  • impedance transformer
  • differential application of pressure to round and oval windows

= amplify sound in air to bring it more like sound in water (in water there is a lot more energy therefore lower displacement of the oval window occurs to transmit the sound)

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25
Q

what does the round window do?

A
  • prevents echoing
  • acts as a beach for fluid
26
Q

what happens when the oval window vibrates?

A

sets up a wave in the perilymph fluid which travels through the cochlea and ends at the round window

27
Q

what hair cells are embedded in Reissner’s (vestibular) membrane?

A

outer hair cells

28
Q

the trained human ear can detect what frequency of change?

A

0.75Hz

29
Q

outer vs inner hair cells

A

outer — motor nerve fibres, embedded into Reissner’s membrane
inner — sensory nerve fibres

30
Q

two angstroms (0.1 nanometre) deflection fo sterocilia auses depolarisation via movement of _____?

A

potassium

31
Q

what is the function of outer hair cells?

A

= muscular (not for hearing)
- tense tectorial membrane (when basilar membrane vibrated with sound) —> focuses the resonant frequency of the basilar membrane so you can hear the difference between smaller changes in frequency

32
Q

what do inner hair cells do?

A
  • they are the original sensors of sound
  • depolarise when the hair moves 2 angstroms in fluid movement in organ of corti
33
Q

which fluid is rich in K+?

A

endolymph

34
Q

what contracts to stiffen the organ of corti and fine tune the frequency of hearing?

A

OHCs

35
Q

what are the 2 types of hearing impairment?

A
  • conductive
  • sensori-neural
36
Q

what parts of the ear do the 2 types of hearing impairment involve?

A
  • conductive — the external and middle ear
  • sensori-neural — the sensation of hearing sound in the cochlea and associated nerve pathway
37
Q

can wax cause a conductive hearing impairment?

A

only when the wax completely occluded the external ear canal

38
Q

what is perichondritis? what kind of hearing impairment does it cause?

A

= an infection of the tissue lining your ear cartilage — normally due to pseudomonas aeruginosa
- swelling in external ear canal —> conductive hearing impairment

39
Q

in sensorineural deafness, what is the typical impact on hearing?

A

= a patient may have complete inability to hear tone at all frequencies
= a patient may have complete inability to hear tone at a particular frequency

40
Q

in conductive deafness, what is the typical impact on hearing?

A

= a patient can hear tones, but only at a higher amplitude (dB)

41
Q

sensorineural hearing loss is related to problems in the inner ear. what are some examples of causes of sensorineural deafness?

A
  • exposure to loud noises
  • infection/inflammation
  • head trauma
  • ageing (presbycusis)
42
Q

conductive hearing loss is related to problems in the outer or middle ear. what are some examples of causes of conductive deafness?

A
  • infection in ear canal
  • foreign object in ear
  • impacted earwax
  • perforated tympanic membrane
  • fluid in the middle ear
  • ear infection for example otitis media
43
Q

what is the cause of visible bubbles behind the eardrum seen with an otoscope?

A
  • middle ear effusion
  • occur in upper resp infection when mucus fills the middle ear and cannot drain down the eustachian tube
44
Q

what is the name for fluid behind the ear?

A

otitis media with effusion / glue ear

45
Q

what % of children have glue ear at some point?

A

80%

46
Q

what is otosclerosis?

A

disease of ossicles — stapes footplate fuses to skull of oval window — in 1% of population — conductive hearing impairment

47
Q

what is the name of a benign tumour of the cochlear nerve that can cause a sensori-neural deafness?

A

acoustic neuroma

48
Q

which type of hair cell is more sensitive to loud noise? what is the effect of this?

A

outer — more damaged as we age — therefore sound differentiation worsens

49
Q

what is considered profound hearing loss? treatment?

A

85+ dB — hard to treat with a hearing aid — cochlear implant possibly needed

50
Q

what is normal hearing? (dB)

A

up to 25dB

51
Q

what can be useful for spotting fluid behind ear?

A

type B tympanogrm — detection of tympanic membrane permeability

52
Q

what range of frequencies is the normal ear most sensitive?

A

1000-4000 Hz

53
Q

where is the cochlear nucleus?

A

medulla

54
Q

where is medial geniculate body?

A

thalamus

55
Q

where is inferior colliculus?

A

midbrain

56
Q

what are the 5 different areas up to the cortex in the auditory pathway>

A
  • vestibulocochlear nerve
  • cochlear nucleus
  • superior olivary nucleus
  • lateral lemniscus
  • inferior colliculus
57
Q

what tests can be used to separate between conductive and sensori-neural hearing loss?

A

webbers and rinne’s tests

58
Q

describe webbers test

A
  • activate tuning fork then put base of tuning fork against the midline of skull
  • listening for lateralisation of sound
  • no hearing impairment — sound same on both sides
  • conductive — sound louder in affected ear
  • sensori-neural — sound louder in normal ear
59
Q

describe rinne’s test

A
  • activate tuning fork then put base on mastoid process behind ear
  • when sound stops bring tuning fork to the outside of ear and should still hear sound
  • carried out on both ears separately

—> In a normal ear, air conduction is greater than bone conduction, that is to say sound is more efficiently transmitted to the cochlea via air than via bone. So, a patient who hears the tuning fork loudest when it is placed 1cm from the external auditory meatus has a positive Rinne’s test and a person who hears loudest when placed over the mastoid process has a negative Rinne’s test
—> conductive hearing loss = -ve result (bone louder)

60
Q

is a normal ear, is bone or air conduction greater?

A

air

PBL SEM 3 (49 decks)

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