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Sem 3 Neuro > Auditory & Vestibular Systems > Flashcards

Auditory & Vestibular Systems Flashcards

1
Q

What are hair bundles filled with?

A

→ actin and are stiff rods

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2
Q

What do hair cells synapse onto?

A

→ Auditory nerve fibre that projects to the brain

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3
Q

What do hair cells convert?

A

→ Motion of stereocilia into release of neurotransmitter

→ NT is converted into electrical activity

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4
Q

What is the extracellular matrix of the hair cells called?

A

→tectorial membrane

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5
Q

Where is the otoconial membrane?

A

→ In the macula of the vestibular system

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6
Q

Where is the cupula?

A

→ Cristae of vestibular system

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7
Q

How are stereocilia arranged?

A

→ In bundles

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8
Q

What are stereocilia connected by?

A

→ connectors

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9
Q

What are the 3 types of connectors?

A

→ Top connector
→ Shaft connector
→ Ankle links

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10
Q

What connectors are important to transduction?

A

→ tip links

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11
Q

What is the function of lateral link connectors?

A

→ they hold the bundle of stereocilia together to allow it to move as a unit

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12
Q

What is the function of tip links?

A

→ Tension in the tip links distorts the tip of the stereocilia mechanically
→ distortion allows channels to open and close with cilia movement
→ current flows proportionately

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13
Q

Describe how hair cells work

A

→ Tip links open ion channels
→ outside the stereocilia is a fluid called endolymph
→ when tip links deform and pull on the top of the stereocilia they allow in a lot of K+
→ endolymph is high in K+
→ K+ influx depolarises the cell
→ VGCC opens
→ Ca2+ triggers neurotransmitter release at the synapse
→ postsynaptic potential in nerve fibre triggers an action potential

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14
Q

When does depolarisation occur?

A

→ When the hair bundle is pushed towards the tallest stereocilia

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15
Q

When does hyperpolarisation occur?

A

→ When the hair bundle is pushed away from the tallest cilia

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16
Q

What system do fish and amphibians have?

A

→ Lateral line system

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17
Q

What is the function of mechanoreceptors on fish?

A

→ Provides information about movement through water or the direction and velocity of water flow

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18
Q

How do neuromasts function?

A

→ Gelatinous cupula encases the hair bundle and moves in response to water motion

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19
Q

What is the inner ear formed from?

A

→ Semicircular canals from the vestibular system

→ Cochlea

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20
Q

Where do the afferent nerves come from?

A

→ Vestibulocochlear nerve CN VIII

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21
Q

What is linear motion?

A

→ Up, down
→ left and right
→ back and forwards

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22
Q

What is rotation?

A

→ Rolling - shoulder to shoulder
→ pitch - forwards and backwards
→ yaw - side to side

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23
Q

What senses rotation?

A

→ Semicircular canals

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24
Q

What is responsible for sensing roll?

A

→ Posterior semicircular canal

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25
Q

What is responsible for sensing pitch?

A

→ Anterior semicircular canal

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26
Q

What is responsible for sensing yaw?

A

→ Horizontal semicircular canal

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27
Q

Where does the endolymph move?

A

→ In the opposite direction to your head

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28
Q

What does rotation cause in the semicircular canals?

A

→ Fluid motion

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29
Q

What are cilia connected to?

A

→ Gelatinous cupula

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30
Q

Describe what happens in the cupula when motion occurs

A

→ Fluid in the canals lags due to inertia pulling the cupula in the opposite direction to the rotation of the head
→ cilia are displaced and depolarise hair cells

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31
Q

What is the ampulla?

A

→ AN opening with receptors

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32
Q

What does the cupula detect?

A

→ Flow of fluid through the semicircular canal

33
Q

What are the otolith organs sensitive to?

A

→ Linear acceleration

34
Q

How are the hair cells arranged in the utricular macula?

A

→ in a curving way

35
Q

What motion can the saccular macula detect and why?

A

→ up and down motion

→ hair cells are arranged in that way

36
Q

What is on top of the hair cells?

A

→ Rigid otoconia crystals

37
Q

What happens to the crystals when motion occurs?

A

→ Under acceleration the crystal layer is displaced which deflects the cilia

38
Q

Describe the auditory pathway

A 
→ Cochlear nucleus 
→ Olivary complex
→ Lateral lemniscus 
→ Inferior Colliculus 
→ Medial geniculate body 
→ Auditory cortex
39
Q

What type of pressure waves are in the atmosphere?

A

→ Longitudinal

40
Q

What determines wavelength?

A

→ Rate at which compression and rarefaction occur

41
Q

What determines frequency?

A

→ Rate at which pressure cycles between compression and rarefaction

42
Q

What is normal air pressure?

A

→ 100kpa

43
Q

What is the decibel scale?

A

→ Log of ratio relative to 20 micropascals

44
Q

What is the pinna?

A

→ Visible ear

45
Q

What is the function of the pinna?

A

→ Gathers sound from environment and funnels it to the eardrum

46
Q

What is the pinna made from?

A

→ Cartilage and is covered with skin

47
Q

What is the function of the meatus and the concha?

A

→ meatus amplifies low frequency

→ concha amplifies high frequency

48
Q

What is grade I microtia?

A

→ Less than complete development of external ear

→ identifiable structures and a small but present ear canal

49
Q

What is grade II microtia?

A

→ Partially developed ear

→ closed stenotic external ear canal producing conductive hearing loss

50
Q

What is grade III microtia?

A

→ Absence of the external ear
→ small peanut like vestige structure
→ absence of external ear canal and drum

51
Q

What is grade VI microtia?

A

→ Absence of the total ear

52
Q

What does the eardrum vibrate in response to?

A

→ Sound

53
Q

What do the ossicles connect?

A

→ Tympanic membrane to oval window of cochlea

54
Q

What does the malleus connect to?

A

→ Eardrum

55
Q

What does the incus act as?

A

→ A lever

→ malleus pushes it at the top which gives it amplification

56
Q

What does the incus connect to?

A

→ Stapes

57
Q

How does the motion of the eardrum turn into motion of fluid in the cochlea?

A

→ Vibrational movement in the ear drum is transmitted through ossicles and amplified at the incus
→ leads to motion pushing on the oval window of the cochlea

58
Q

What is glue ear?

A

→ Middle ear fills with fluid which impedes motion of the ossicles

59
Q

Why do you lose amplification with glue ear?

A

→ Eardrum is pushing against fluid

60
Q

What are the three chambers in the cochlea?

A

→ Scala vestibuli
→ Scala media
→ Scala tympani

61
Q

What is the basilar membrane?

A

→ between the scala tympanis and the scala media

62
Q

What does the stapes cause?

A

→ Compression of fluid within cochlea

63
Q

What is the cochlea?

A

→ Fluid filled spiral canal divided by a flexible membrane

64
Q

What is the function of the basilar membrane?

A

→ It filters sound according to frequency

65
Q

What is the basilar membrane like at the apex and at the end?

A

→ more rigid at the end closest to oval membrane

→ at the apex it is wide and compliant

66
Q

How does the basilar membrane resonate at the apex and at the end?

A

→ Close to the oval window the basilar membrane resonates at higher frequencies
→ at the other end it resonates at lower frequencies

67
Q

Where is the organ of corti?

A

→ On top of the basilar membrane within the scala media

68
Q

What is the extracellular matrix of the organ of corti?

A

→ Tectorial membrane

69
Q

What does motion of the organ of corti cause?

A

→displacement of stereocilia

70
Q

What hair cells are in contact with the tectorial membrane?

A

→ outer hair cells

71
Q

What does the basilar membrane do to the hair cells?

A

→ Moves up and down and pushes the hair cells towards the tectorial membrane

72
Q

Describe how the cells contract?

A

→ Influx of +ve ions makes the outer hair cells contract
→ when there are increases in voltage the prestin contracts
→ it is on the cell membrane so it causes the entire cell to contract

73
Q

What is prestin?

A

→ A substance that allows the hair cell to be motile

74
Q

Describe the cochlear amplifier?

A

→ basilar membrane moves upwards
→ it pushes against the tectorial membrane which makes the hair cell bundle lean
→ as it leans it opens up the channels on the hair cell
→ this allows an influx of +ve ions
→ the voltage inside the cell increases
→ the cell contracts
→ prestin will be in a short confirmation state
→ basilar membrane is pulled towards the tectorial membrane
→ inner hair cell leans in further which causes the influx of more +ve ions

75
Q

How much does the cochlea amplify by?

A

→ 50 dB

76
Q

What is the intracellular voltage of the hairs?

A

→ negative

77
Q

What is the difference like between intra and extra cellular voltage and why?

A

→ Much larger than other neurons

→ changes in the voltage of haircells are much more rapid

78
Q

What ion is in high concentration in the scala media?

A

→ K+

Sem 3 Neuro (21 decks)

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