hearing

Question 1

which membrane separates the scala media from the scala vestibuli?

Answer 1

reisner’s membrane

Question 2

which membrane separates the scala media from the scala tympani?

Answer 2

basilar membrane

Question 3

what does the scala media contain?

Answer 3

endolymph = high k+ low ca2+

Question 4

what is the stria vascularis

Answer 4

actively transports K+ into scala media

Question 5

deiter’s cells

Answer 5

supporting cells below OHCs

Question 6

pillar cells

Answer 6

supporting cells in between IHCs and OHCs

Question 7

type I afferents

Answer 7

carry information from IHCs to brain

Question 8

type II afferents

Answer 8

carry information from OHCs to brain

involved in nociception

Question 9

lateral efferents

Answer 9

synapse onto type I fibres

switches off type I fibres to protect from overactivity

Question 10

medial efferents

Answer 10

synapse directly onto OHCs

inhibitory

Question 11

tonotopic organisation of cochlea

Answer 11

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

Question 12

what is the human hearing range?

Answer 12

20Hz - 200Khz

Question 13

describe what happens when the hair cell is at rest

Answer 13

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

Question 14

describe what happens when the hair cell is excited

Answer 14

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

Question 15

describe what happens when the hair cell is inhibited

Answer 15

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

Question 16

where are the ion channels located on the stereocilia

Answer 16

shorter rows of stereocilia

Question 17

what is a synaptic ribbon?

Answer 17

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

Question 18

what is the role of OHCs?

Answer 18

cochlear amplification

Question 19

Prestin

Answer 19

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

Question 20

how are type II afferents involved in nociception

Answer 20

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

Question 21

which marker is present in both hair cells?

Answer 21

myosin 7a

Question 22

which marker is expressed in IHCs?

Answer 22

otoferlin

Question 23

which marker is expressed in all fibres in cochlea?

Answer 23

βIII-tubulin

Question 24

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

Answer 24

sound localisation

Question 25

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

Answer 25

sound recognition