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Neuro > Auditory System > Flashcards

Auditory System Flashcards

1
Q

What is sound

A

Displacement of air particles following a sinusoidal pattern of compression and rarefraction

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2
Q

Amplitude

A

Loudness of sound

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3
Q

Frequency of wavelength

A

Pitch

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4
Q

Range of human hearing

A

20Hz—> 20KHz

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5
Q

Auditory system components

A

Outer ear
Middle ear
Inner ear
Central auditory pathways

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6
Q

Which parts of the ear contain air

A

Outer and middle ear

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7
Q

Which parts of the ear contain fluid

A

Inner ear

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8
Q

Epithelial lining of Eustachian tube

A

Respiratory epithelium

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9
Q

Pinna

A

Unique to every individual
Cartilaginous structure

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10
Q

Function of folds of Pinna

A

Directs sound waves into the ear canal
High pitch>low pitch

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11
Q

Ossicles

A

Malleus
Incus
Stapes

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12
Q

When are the ossicles fully formed

A

At birth

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13
Q

Middle ear contains

A

Bones- ossicles
Muscles- tensor tympani and stapedius
Eustachian tube

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14
Q

Which nerve passes through the internal auditory meatus

A

Facial nerve (CN VII)

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15
Q

Which Foramen does the facial nerve leave the ear cavity

A

Stylomastoid foramen

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16
Q

Role of the middle ear

A

Acoustic impedance match
Between air and fluid-filled ear

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17
Q

What percentage of energy is lost when transferred from air to fluid

A

97%

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18
Q

How does the middle ear amplify sound

A

Amplifying the movement:
Ratio area - tympanic membrane: stapes 14:1
Lever action of ossicles
Malleus>incus

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19
Q

How much louder does the middle ear make sound

A

20-35 Db

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20
Q

Role of middle ear- increase in pressure

A

200 fold increase boost in pressure from tympanic membrane to inner ear

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21
Q

Role of muscles in middle ear

A

Protection of the inner ear from acoustic trauma
Stiffens the ossciular chain

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22
Q

How is the Stapedius stimulated

A

Acoustically
Reflex arc: 3 or 4 neurones

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23
Q

Length of the Stapedius reflex

A

25 ms (thunderclap not shotgun)

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24
Q

When is the tensor tympani stimulated

A

Voluntary and involuntary control
Stiffens when chewing

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25
Q

Role of the Eustachian tube

A

Ventilation if the middle ear space
Drainage of secretions

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26
Q

Inner ear

A

A set of fluid filled sacs encased in bone

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27
Q

Role of cochlear

A

Hearing

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28
Q

Role of labyrinth

A

Balance

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29
Q

Innervation of inner ear

A

Vestibulocochlear nerve

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30
Q

Cochlea

A

2.5 turns fluid filled bony tube

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31
Q

2 openings of cochlea

A

Round window
Oval windoe

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32
Q

3 compartments of cochlea

A

Scala tympani
Scala media
Scala vestibuli

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33
Q

2 ionic fluids of cochlea

A

Endolymph
Perilymph

34
Q

Endolymph

A

Scala media
High K+
Low Na+

35
Q

Perilymph

A

Scala vestibuli/tympani
Like ECF and CSF
Na+ rich
Low K+

36
Q

How is ion gradient maintained between cochlear fluids

A

Na/K ATPase
NKCC1 CIC-K chloride channels

37
Q

Ion channel abnormalities

A

Deafness

38
Q

Helicotrema

A

Small hole at the end of the cochlea
Allows movement of pressure wave of fluid in cochlea

39
Q

Basilar membrane

A

Separates Scala media from Scala tympani
Moves when pressure waves hit it- transfers mechanical energy into chemical energy

40
Q

Properties of basilar membrane

A

Narrow at base
Wide at apex

Stiff at base
Floppy at apex

High frequencies detected at base
Low frequencies at apex

41
Q

What frequencies are detected at base of basilar membrane

A

High

42
Q

What frequencies are detected at apex of basilar membrane

A

Low

43
Q

Tonotopy

A

Differential movements of the basilar membrane at different areas of the cochlea due to different frequencies
Each nerve responds maximally at a specific frequency
Outer hair cells can alter the stiffness of the basilar membrane to ensure maximal stimulation at one site and a dampened response at another
Increased resolution

44
Q

Components of Scala media

A

Organ of corti
Inner and outer Hair cells
Tectorial membrane

45
Q

Tectorial membrane

A

Fixed

46
Q

Organ of corti

A

Contains inner hair cells anchored into tectorial membrane by stereocilla and outer hair cells
Cochlea nerve fibre attached to inner hair cells

47
Q

How are sound waves transferred to electrical energy in organ of corti

A

Displacement of the basilar membrane causes movement of specialised mechanical transducing cells- inner hair cells
Movement of inner hair cells causes activation of the auditory nerve—> activated the central auditory pathway

48
Q

Role of inner hair cells

A

Mechanical transduction

49
Q

Role of outer hair cells

A

Fine tuning of sound by stiffening the basilar membrane in areas where the cochlea is not maximally stimulated

50
Q

From waves to sparks

A

Movement of stereocillia
Rapid response required
Mechanically gated K+ channels open causing depolarisation (K+ Endolymph)
Depolarisation results in opening of voltage gated calcium channels
Release of neurotransmitter (mainly glutamate)
Repolarisation through K+ efflux (into K+ poor Perilymph)

51
Q

Central auditory pathway

A

Cochlea —> cochlear nerve —> medial geniculate body —> auditory cortex

52
Q

How do we localise sound

A

Interaural time difference
Interaural intensity difference

53
Q

Interaural time difference

A

MSO neurones are coincident detectors- respond only when excitatory signals arrive simultaneously
anatomical differences in connectivity allow each MSO neuron to be sensitive to sound source from particular location

54
Q

Ear canal

A

1/3 cartilage
2/3 bone

55
Q

Formation of Pinna and ear canal

A

Forms between 10th and 18th week in utero
Formed from pharyngeal arches 1 and 2 (6x Hillocks of His)

56
Q

How is frequency (pitch) encoded

A

In nerves by location along the basilar membrane

57
Q

How is intensity (loudness) encoded

A

In nerves by numbers responding and by firing rate

58
Q

Sound transduction

A

By inner hair cells (and outer hair cells)

59
Q

How is sound amplified

A

Outer hair cells

60
Q

From neuron to brain

A

Auditory fibre- spiral ganglion
Spiral ganglion to cochlear nerve (CN VIII)
Central auditory pathway

61
Q

Conductive hearing loss

A

Defective outer or middle ear

62
Q

Sensorineural hearing loss

A

Defective inner ear

63
Q

Treatment of conductive hearing loss

A

Depends on the cause = improve conduction
eg drain middle ear fluid
Remove wax
Bypass the conductive mechanism

64
Q

Constitution of Perilymph

A

High sodium and low potassium content

65
Q

Afferent arm of pupillary light reflex

A

Optic nerve —> pretectal nucleus —> Edinger-Westphal nucleus

66
Q

Organ of corti

A

specialised structure which rests on the basilar membrane

67
Q

Semi-circular canals

A

Pouring ice cold water in the external auditory meatus can cause convection currents in the semicircular canals and nystagmus

68
Q

Utricle and Saccule

A

Signal the position of the head at rest (i.e. when no movement is occurring).

69
Q

Sensation to middle ear

A

Glossopharyngeal nerve

70
Q

Type of joints between chain of 3 ossicles

A

Synovial

71
Q

During aging

A

High tone deafness occurs first (presbycusis)

72
Q

Function of semi-circular canals

A

Detect rotational acceleration and deceleration

73
Q

Otolithic organs (utricle and saccule) function

A

Detect gravity and liner acceleration

74
Q

Arrangement of semi-circular canals

A

3 different planes- roughly orthogonal

75
Q

The semi-circular canals affect movement in

A

Both eyes simultaneously

76
Q

What fills the utricle and saccule

A

Endolymph

77
Q

After a morning of lectures you walk outside to see luis a medical student dancing non stop on the benches. Seeing a crowd gather he then proceeded to perform 5 perfect pirouettes in consistent succession(spinning round in circles) which resulted in him falling over due to dizziness.

Which organ of the vestibular system detects angular acceleration(head spinning round)?

A

Semicircular canals

78
Q

Saccule function

A

verticle movements (imagine adding a sack to someone before you throw them over a bridge)

79
Q

Utricle function

A

horizontal movements

80
Q

Plate of stapes

A

in conduction system of sound via the bones malleus incus stapes(MIS- in order)

Neuro (22 decks)

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