hearing Flashcards

1
Q

which membrane separates the scala media from the scala vestibuli?

A

reisner’s membrane

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2
Q

which membrane separates the scala media from the scala tympani?

A

basilar membrane

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3
Q

what does the scala media contain?

A

endolymph = high k+ low ca2+

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4
Q

what is the stria vascularis

A

actively transports K+ into scala media

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5
Q

deiter’s cells

A

supporting cells below OHCs

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6
Q

pillar cells

A

supporting cells in between IHCs and OHCs

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7
Q

type I afferents

A

carry information from IHCs to brain

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8
Q

type II afferents

A

carry information from OHCs to brain

involved in nociception

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9
Q

lateral efferents

A

synapse onto type I fibres

switches off type I fibres to protect from overactivity

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10
Q

medial efferents

A

synapse directly onto OHCs

inhibitory

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11
Q

tonotopic organisation of cochlea

A

cells at base of cochlea respond to high frequency sounds
cells at apex of cochlea respond to low frequency sounds
hair cells send information to the cochlea nucleus in the brain. same tonotopic organisation is preserved

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12
Q

what is the human hearing range?

A

20Hz - 200Khz

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13
Q

describe what happens when the hair cell is at rest

A
  1. resting tension opens some transducer channels
  2. some k+ enters cell and depolarises membrane slightly = -55mV
  3. depolarisation activates some Ca2+ channels
  4. resting activity in afferent fibre produced
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14
Q

describe what happens when the hair cell is excited

A
  1. hair cell is stimulated + hair bundle pushed towards tallest stereocilia
  2. increased tension in tiplinks opens all channels in hair bundle
  3. hair cell is depolarised which opens majority of Ca2+ channels
  4. a lot of neurotransmitter released onto afferent fibres
  5. increased firing rate of afferent fibre
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15
Q

describe what happens when the hair cell is inhibited

A
  1. hair cell is stimulated so hair bundle pulled away from tallest stereocilia
  2. decreased tension in tip links closes all transducer channels
  3. outward flow of k+ through k+ channels hyperpolarises cell
  4. no ca2+ channels open
  5. reduced firing rate of afferent fibre
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16
Q

where are the ion channels located on the stereocilia

A

shorter rows of stereocilia

17
Q

what is a synaptic ribbon?

A

specialised electron dense bodies in synaptic region of hair cell
store of synaptic vesicles to maintain high rates of exocytosis for a long time

18
Q

what is the role of OHCs?

A

cochlear amplification

19
Q

Prestin

A

motor protein in OHC membrane allowing OHC to contract or elongate in response to Cl- movement

20
Q

how are type II afferents involved in nociception

A

active when all OHCs they innervate are active –> produces dangerously loud sound
signals to brain to turn cells off via efferent fibres

21
Q

which marker is present in both hair cells?

A

myosin 7a

22
Q

which marker is expressed in IHCs?

A

otoferlin

23
Q

which marker is expressed in all fibres in cochlea?

A

βIII-tubulin

24
Q

what is the pathway from the ventral cochlear nucleus important for?

A

sound localisation

25
Q

what is the pathway from the dorsal cochlear nucleus important for?

A

sound recognition