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Physiology > Hearing + Ear (I) > Flashcards

Hearing + Ear (I) Flashcards

1
Q

What is sound

A

A longitudinal pressure wave travelling through air or a medium

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2
Q

Which 2 characteristics make up sound

A

Frequency (pitch)

Amplitude (intensity/loudness)

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3
Q

How do you work out frequency

A

1/t

T = period between sounds

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4
Q

What would high frequency t be

A

Smaller intervals between sound

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5
Q

What would increase in pressure cause for intensity

A

Increased pressure increases intensity of sound

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6
Q

Does t change measuring intensity

A

No. Period of sound is same

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7
Q

How do you work out intensity of sound (decibels) from pressure (pa)

A

20 log (pa/20)

20 is a reference level

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8
Q

Why is 20pa pressure only 0 decibels

A

Intensity measured in log

Log 20 (20/20) = 0

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9
Q

Is frequency dependent on pressure

A

Not always, we can detect a high frequency even at lower pressures

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10
Q

at what frequency pitch does intensity need to be highest

A

At high and low frequencies

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11
Q

What makes up the outer ear

A

Pinna

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12
Q

Which part of ear allows detection of sound externally and also on all vertical plates (ie left right up down)

A

Pinna outer ear

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13
Q

Which part of ear conducts sound to middle ear from the pinna

A

Ear canal

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14
Q

What does the ear canal allow and why

A

Amplification / increase intensity of sound due to its resonance

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15
Q

Where does the outer ear terminate

A

Tympanic membrane

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16
Q

What allows equal pressure on either sides of tympanic membrane allowing sound / vibrations

A

Eustachian tube opening (not open in air flights = no pressure equilibrium)

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17
Q

What makes up the middle ear

A

Ossicles

Malleus , incus and stapes foot plate

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18
Q

Which part of the middle ear is the longest

A

Malleus

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19
Q

What are the inner ear ossicles for

A

Transfer of vibrations to the cochlea via the stapes foot plate

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20
Q

How is the stapes foot plate attached to the cochlea

A

Via the cochlea oval window

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21
Q

Middle ear allows sound waves to travel from air to liquid cochlea. What is this called

A

An impedance transformer

22
Q

Why is there increased pressure at the stapes than at the tympanic membrane (overcoming gas to liquid)

A

Tympanic membrane has a larger area

But both stapes and TM have the same force applied (stapes lower area so more force in a smaller area = higher pressure )

Pressure = force / area

23
Q

By how much is pressure increases in stapes

A

X 18

24
Q

Why is the fact malleus is longer than incus a way to affect pressure and therefore gas liquid barrier

A

Acts as a lever

When force is applied to malleus this increases force of incus acting on stapes

25
Q

What is the total increase in pressure in the middle ear due to lever and area

A

X25

26
Q

Which cranial nerve is attached to cochlea

A

VIII

27
Q

What are the 3 Scala filled with fluid in the cochlea

A

Scala tympani

Scala media (in middle)

Scala vestibuli

28
Q

Which membrane separates Scala media from tympani

A

Basilar membrane

29
Q

What fluid is present in the Scala tympani and vestibuli

A

Perilymph (high Na)

30
Q

What fluid fills Scala media

A

Endolymph (high K)

31
Q

Which membrane apart from basilar is between the Scala media and tympani

A

Tectorial

32
Q

Which cells in the Scala media produce endolymph (k)

A

Stria vascularis

33
Q

Which area does transduction or sounds to electrical signals happen

A

Organ of Corti (between the basilar membrane and tectorial) ie Scala media and tympani

34
Q

Which fluid surrounds the apical (top) of the outer hair cells in organ of corti

A

Endolymph from the start of media

35
Q

Which fluid surrounds the bottom of the outer hair cells

A

Perilymph from the Scala tympani

36
Q

What is connected to hair cells in organ of corti

A

Nerve fibres

37
Q

From stapes , where does sound vibrate down

A

From base to apex of the cochlea

38
Q

What is pressed down due to pressure of the vibration sounds in the cochlea

A

The Scala media (basilar membrane being pressed down on)

39
Q

If sound was at high frequency, where would maximal displacement be

A

At base (start of cochlea)

40
Q

What frequency would it be if maximal displacement happened at apex of the cochlea(end)

A

Low freq

41
Q

What does displacement of basilar membrane which therefore moves tectorial membrane cause

A

Hair cells to move

42
Q

What are hairs on hair cells called

A

Stereocilia

43
Q

What happens when inner hair cells stereocilia are excited

A

K moves in through the mechanically gated K channels (from endolymph)

Causes depolarisation of the cell (+ve charge)

Causes ca to enter and Nt vesicle fuse and release

Causes excitation of nerves

44
Q

Why can K enter from the endolymph

A

The cell has a more negative membrane potential (-40) vs outside is 80+

45
Q

When is K entrance into stereocilia regular amount

A

When hair cells are vertical

46
Q

What happens if stereocilia bend towards the longest one

A

Links between the cilia stretch and cause more mechanically gated K channels to open

47
Q

When is K entrance into cells stopped

A

Bending towards the shortest stereocilia blocks the mechanically gated K channels = no neurone excitation

48
Q

How are outer hair cells response to sound different

A

They shorten and lengthen (not bend)

49
Q

Which proteins allow shortening and lengthening of outer hair cells

A

Prestin

50
Q

What does outer hair cell movements do

A

Causes even more displacement of the basilar membrane causing even more depolarisation at the inner hair cells

Physiology (31 decks)

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