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BAB > L08: Hearing > Flashcards

L08: Hearing Flashcards

1
Q

What structures does the outer ear contain

A

Pinna
Auditory canal
Tympanic membrane

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2
Q

What structures does the middle ear contain

A

Ossicles (3 small. Bones)

A connection to the Eustachian tube

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3
Q

What structures does the inner ear contain

A

Cochlear

Semilunar canals

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4
Q

What are the 3 small bones that form the ossicles

A

Malleus
Incus
Stapes

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5
Q

What is the 2 roles of the 3 small bones in the middle ear

A
  • Transmit sound wave form the tympanic membrane to the oval window of the inner ear
  • amplify the sound they transmit the sound
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6
Q

What is the oval window

A

The window that allows connection of the stapes bone to the inner ear

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7
Q

How is the mechanism to reduce amplification of loud sound achieved

A

By 2 muscles of middle ear

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8
Q

What are the 2 muscles of the middle ear

A

Strapedious muscle

Tensor tympani muscle

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9
Q

What happens to these 2 muscles where there is loud sound

A

Contract

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10
Q

What does the contraction of the 2 muscles allow

A

Stop amplification of sound via 3 bones- attenuation reflex

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11
Q

What are the 3 tubes in the cochlear known as

A

Scala vestibuli
Scala media
Scala tympani

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12
Q

What does the scala media contain

A

Organ of corti

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13
Q

What lining separtes the scala media and scala tympani

A

Basilar membrane

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14
Q

Where does the scala tympani and scala vestibuli connect to

A

Helicotrema (a hole at apex of ear)

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15
Q

What liquid found inside the scala media

A

Endolymph

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16
Q

What happens to the endolymph when the stapes pushes the oval window membrane in the cochlear

A

The endolymph moves back and forth

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17
Q

As the endolymph moves what structure does it also move

A

The basilar membrane

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18
Q

How does the rigidity of the basilar membrane change along its length

A

From narrow and stiff (at base) to wider and floppy (at apex)

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19
Q

Which type of sound influences the apex

A

Low frequency sound

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20
Q

What type of sound influences the base

A

High frequency sound

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21
Q

Where is the organ of orti located

A

In the scala media on the basilar membrane

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22
Q

Therefore when the basilar membrane moves what happens to the organ of corti

A

Organ of corti moves as the basilar membrane moves

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23
Q

What type of cells are found at the organ of corti

A

Hair cells

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24
Q

What membrane does the hair cells touch

A

Tectorial membrane

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25
Q

What structure does the tectorial membrane also sit on top of

A

Sterocilia

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26
Q

What is the sterocilia

A

A structure that sits on the hair cells

27
Q

As the organ of corti moves what happens to the tectorial membrane

A

It moves

28
Q

As the tectorial membrane moves what happens to the sterocilia

A

Moves

29
Q

What happens when sterocilia bend in and out

A

Open different ion channels

30
Q

If ion channels open on the hair called as a result of sterocilia bending what happens to the hair cells

A

Depolarisation

31
Q

On the outer/inner hair cell which specific channel opens to cause depolarisation as the stereocilia moves

A

Mechanically gates pottasium channels

32
Q

What happens to potassium when the mechanically gated potassium channels open

A

Potassium influx into the outer hair cell

33
Q

When there is a depolarisation in the outer/inner hair cell what channel opens

A

Voltage gated calcium channels

34
Q

What does calcium influx as a result of voltage gated calcium channels cause

A

Exocytosis of neurotransmitters (glutamate) in the pre-synaptic vesicles to the spiral ganglion neurite

35
Q

What does glumate get released to

A

Spiral ganglion neuritis

36
Q

What do many spiral ganglion cells form

A

The auditory nerve

37
Q

How many spiral ganglion cells transmit a signal from inner hair cell

A

Many (divergent)

38
Q

How many spiral ganglion cells connect to outer hair cells

A

Small number (convergent)

39
Q

What is the main role of outer hair cells of the organ corti

A

Amplify sound for inner hair cells

40
Q

How does outer hair cells amplify sound

A

1) Outer hair cells have motor proteins that contract and relax
2) when the motor protein contracts it pulls the stereocilia into one direction
3) pulling the stereocilia pulls the tectorial membrane with it
4) this amplify the sound by the inner hair cells

41
Q

What is tonotopy

A

Because the basilar membrane has different rigidity along its length from base to apex, every part of the membrane is responsive to a characteristic frequency that the hair cells are sensitive to

42
Q

What does the tonotopy organisation allow us to do

A

Distinguish sound at different frequency

43
Q

What is a characteristic frequency

A

Highest spikes the hair cell can produce in repsonse to its frequency that it is specific to

44
Q

Which ascending pathway takes the info from the ear to the brain

A

Auditory pathway

45
Q

Which side of the brain does info from the left ear go to

A

Both sides of the brain i.e left and right

46
Q

What side of the brain does info form the right ear go to

A

Both sides of the brain i.e left and right

47
Q

Where does info form the auditory pathway go to

A

Auditory cortex

48
Q

How is the auditory cortex organised

A

Tonotopy

49
Q

What does tonotopy of the auditory cortex mean

A

Specific frequency terminate at specific regions of the auditory cortex that correlates to that frequency

50
Q

What is the primary auditory cortex surrounded by

A

Secondary auditory cortex

51
Q

What is phase locking

A

Firing an action potential with every cycle of frequency sound

52
Q

When does phase locking occur

A

In low frequency sound

53
Q

Why is phase locking not possible in high frequency

A

The sensory neurones cannot be continuously stimulates to produce rapid cycles of action potential

54
Q

What limits the phase locking in high frequency sound

A

Refractory period of the nerve cells

55
Q

What do we rely on for high frequency sounds if phase locking doesn’t occur

A

Tonotopy (organisation of the auditory system)

56
Q

In loud sound what is the firing of spikes like

A

High

57
Q

In soft sound what is the firing of spike like

A

Low firing

58
Q

How can we localise sound

A

Message from the ipsilateral ear goes to the superior Olive quickly than the message from the other ear which reaches the superior olive slower due to it needing to pass to the other side = interaural delay

59
Q

What is another way of localising sound

A

When sound waves hit your head it creates a sound shadow, so the contralateral ear has a lower intensity than the ipsilateral ear,

60
Q

What is nerve deafness

A

Damage to the inner ear or auditory pathway

61
Q

What are the 3 main causes of nerve deafness

A

Genetic disorder: affected hair cell structures
Congenital: congenital rubella syndrome, toxoplasmosis- lead to hypoplastic auditory nerves
Presbycusis: normal age related loss (not reversible)

62
Q

What is acquired nerve deafness

A

Cochlear damage due to noise from environment or occupation

63
Q

Which drugs can damage the ear

A

Aminoglycosides (anitbiotics)

Methotrexate (immunosuppressant drugs)

64
Q

If the motor proteins in the outer hair cell contracts when there is no sound what can this cause

A

Tinnitus i,e noisy ear

BAB (21 decks)

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