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Physiology > The ear and hearing > Flashcards

The ear and hearing Flashcards

1
Q

What are the two systems of the ear?

A
  • Vestibular system

- Auditory system

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2
Q

What is the function of vestibular system in information?

A

Inform the brain of the position of head and body and how they are moving

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3
Q

Function of vestibular system

A

Balance

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4
Q

Function of auditory system info

A

Detect sounds
Locate them in space
Identify sound nuances

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5
Q

Function of auditory system

A

Hearing

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6
Q

What does pitch (tone) depend on?

A

Frequency

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7
Q

What does intensity (loudness) depend on?

A

Amplitude

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8
Q

What does timbre (quality) depend on?

A

Overtones

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9
Q

What is sound amplitude expressed in>

A

db

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10
Q

What is sound amplitude expressed in>

A

db

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11
Q

What is the auditory threshold?

A

0db

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12
Q

Auditory system pathway

A

Sound waves move tympanic membrane ➡
Tympanic membrane moves ossicles ➡
Ossicles move oval window membrane ➡
Movement in oval window moves fluid in cochlea ➡
Fluid in cochlea induces response in sensory neurons

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13
Q

Auditory system stimulus pathway

A

Auditory Receptors (Cochlea) ➡ Brainstem ➡ Thalamus (Medial geniculate nucleous-MGN ➡ Primary Auditory Cortex

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14
Q

Pressure in oval window vs tympanic membrane

A

Greater pressure (force/surface) in the oval window than in the tympanic membrane,

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15
Q

What happens after a loud sound? (attenuation reflex)

A

The brain will diminish hearing sensitivity by tensing the muscles → impairment of amplification system

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16
Q

Attenuation reflex

A
  • Protection (delayed)
  • Adaptation to loud sounds
  • Not hearing our own speech
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17
Q

Where are malleus and stapes linked and how?

A

Link to skull by muscles

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18
Q

What communicates at apex?

A

Scala vestibuli and scala tympani

19
Q

Where does perilymph flow from?

A

From vestibuli to tympany when stapes taps the oval window

20
Q

Where does endolymph flow?

A

Inside the scala media

21
Q

Basilar membrane at apex is ..

A

Wider and more flexible

22
Q

When perilymph is displaced…

A

Displaces endolymph (vestibular membrane very flexible) and generating waves in the basilar membrane.

23
Q

Where are high frequencies detected?

A

Near oval window narrow and stiff

24
Q

Where are low frequencies detected?

A

Near apex wide and flexible

25
Q

Frequency discrimination in

the cochlea diagram

A
26
Q

Inner ear: Transduction pathway

A

A. Upward displacement of basilar membrane creates a shearing force that leads to lateral displacement of the stereocilia
B. Mechanical displacement of the stereocilia in a lateral direction cause depolarization of the hair cell.
C. Downward displacement of the basilar membrane creates shearing force that results in lateral displacement of the stereocilia in the opposite direction hyperpolarization of the hair cell.

27
Q

What does perilymph have a similar composition to?

A

Cerebral spinal fluid

27
Q

What does perilymph have a similar composition to?

A

Cerebral spinal fluid

28
Q

Endolymph in scala media ion concentration

A

High K+ and low Na+

29
Q

Ion channel in inner ear transduction

A

Mechanically gated ion channel

30
Q

How is the inner ear mechanically gated ion channel connected?

A

In different stereocilia by an elastic filament (tip-link)

31
Q

Cilia bending in one direction in inner ear

A

Channel opens: K+ influx and cell depolarization

32
Q

Cilia straight in inner ear

A

Channel semi-closed: K+ influx at resting potential

33
Q

Cilia bending in opposite direction in inner ear

A

Channel closed: cell hyperpolarization

34
Q

What does channel opening lead to and why?

A

K+ influx because of the exceptionally high [K+] in the endolymph!

35
Q

What do most of fibres in auditory nerve innervate?

A

Inner hair cells, and the contribution of outer cells is somehow small

36
Q

What are fibres in auditory nerve

A

Axons of Spiral ganglion cells

37
Q

Amplification system by outer hair cells

A
  • Sound depolarizes the outer hair cell
  • That change in membrane potential induces the cell to shorten or lengthen (electromotility)
  • The change on length amplifies the movement of the basilar membrane
38
Q

NB!! Mechanism of hearing

A
  1. Sound waves induce oscillation in the tympanic membrane
  2. Pressure waves are transmitted through the ossicles to the oval window
  3. Pressure on the oval window induces movement of the basilar membrane
  4. Displacement of the basilar membrane depolarizes hair cells (sensory cells)
  5. Depolarization of outer hair cells change their morphology, amplifying the signal
  6. Depolarization of inner hair cells induce neurotransmitter release
  7. Neurotransmitter evokes AP in the auditory (cochlear) nerve
39
Q

What are hair cells innervated by?

A

An efferent fibre

40
Q

Acetylcholine function in hearing

A

Can induce hair cell hyperpolarization, reducing the sensitivity of the cochlea locally

41
Q

When is a cochlear implant useful?

A

When cause of deafness is sensory-neural (damage/death of hair cells but mostly functioning auditory nerve)

42
Q

NB! Describe cochlear implant

A

Headpiece with microphone (converts sound into electrical signals), digital processor, a radio transmitter (conveys a digital code to an internal receiver). The receiver will send electrical impulses through electrodes that enter the cochlea and stimulate the auditory nerve → from base to apex
- Uses natural tonotopy to differentiate frequencies

43
Q

Cochlear implant diagram

A

Physiology (28 decks)

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