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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
Role of the Eustachian tube
Ventilation if the middle ear space Drainage of secretions
26
Inner ear
A set of fluid filled sacs encased in bone
27
Role of cochlear
Hearing
28
Role of labyrinth
Balance
29
Innervation of inner ear
Vestibulocochlear nerve
30
Cochlea
2.5 turns fluid filled bony tube
31
2 openings of cochlea
Round window Oval windoe
32
3 compartments of cochlea
Scala tympani Scala media Scala vestibuli
33
2 ionic fluids of cochlea
Endolymph Perilymph
34
Endolymph
Scala media High K+ Low Na+
35
Perilymph
Scala vestibuli/tympani Like ECF and CSF Na+ rich Low K+
36
How is ion gradient maintained between cochlear fluids
Na/K ATPase NKCC1 CIC-K chloride channels
37
Ion channel abnormalities
Deafness
38
Helicotrema
Small hole at the end of the cochlea Allows movement of pressure wave of fluid in cochlea
39
Basilar membrane
Separates Scala media from Scala tympani Moves when pressure waves hit it- transfers mechanical energy into chemical energy
40
Properties of basilar membrane
Narrow at base Wide at apex Stiff at base Floppy at apex High frequencies detected at base Low frequencies at apex
41
What frequencies are detected at base of basilar membrane
High
42
What frequencies are detected at apex of basilar membrane
Low
43
Tonotopy
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
Components of Scala media
Organ of corti Inner and outer Hair cells Tectorial membrane
45
Tectorial membrane
Fixed
46
Organ of corti
Contains inner hair cells anchored into tectorial membrane by stereocilla and outer hair cells Cochlea nerve fibre attached to inner hair cells
47
How are sound waves transferred to electrical energy in organ of corti
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
Role of inner hair cells
Mechanical transduction
49
Role of outer hair cells
Fine tuning of sound by stiffening the basilar membrane in areas where the cochlea is not maximally stimulated
50
From waves to sparks
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
Central auditory pathway
Cochlea —> cochlear nerve —> medial geniculate body —> auditory cortex
52
How do we localise sound
Interaural time difference Interaural intensity difference
53
Interaural time difference
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
Ear canal
1/3 cartilage 2/3 bone
55
Formation of Pinna and ear canal
Forms between 10th and 18th week in utero Formed from pharyngeal arches 1 and 2 (6x Hillocks of His)
56
How is frequency (pitch) encoded
In nerves by location along the basilar membrane
57
How is intensity (loudness) encoded
In nerves by numbers responding and by firing rate
58
Sound transduction
By inner hair cells (and outer hair cells)
59
How is sound amplified
Outer hair cells
60
From neuron to brain
Auditory fibre- spiral ganglion Spiral ganglion to cochlear nerve (CN VIII) Central auditory pathway
61
Conductive hearing loss
Defective outer or middle ear
62
Sensorineural hearing loss
Defective inner ear
63
Treatment of conductive hearing loss
Depends on the cause = improve conduction eg drain middle ear fluid Remove wax Bypass the conductive mechanism
64
Constitution of Perilymph
High sodium and low potassium content
65
Afferent arm of pupillary light reflex
Optic nerve —> pretectal nucleus —> Edinger-Westphal nucleus
66
Organ of corti
specialised structure which rests on the basilar membrane
67
Semi-circular canals
Pouring ice cold water in the external auditory meatus can cause convection currents in the semicircular canals and nystagmus
68
Utricle and Saccule
Signal the position of the head at rest (i.e. when no movement is occurring).
69
Sensation to middle ear
Glossopharyngeal nerve
70
Type of joints between chain of 3 ossicles
Synovial
71
During aging
High tone deafness occurs first (presbycusis)
72
Function of semi-circular canals
Detect rotational acceleration and deceleration
73
Otolithic organs (utricle and saccule) function
Detect gravity and liner acceleration
74
Arrangement of semi-circular canals
3 different planes- roughly orthogonal
75
The semi-circular canals affect movement in
Both eyes simultaneously
76
What fills the utricle and saccule
Endolymph
77
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)?
Semicircular canals
78
Saccule function
verticle movements (imagine adding a sack to someone before you throw them over a bridge)
79
Utricle function
horizontal movements
80
Plate of stapes
in conduction system of sound via the bones malleus incus stapes(MIS- in order)

Neuro (22 decks)

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