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BRS Year 2 > Auditory & Vestibular system > Flashcards

Auditory & Vestibular system Flashcards

1
Q

where is the ear in relation to the skull?

A

embedded in petrous portion of temporal bone

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2
Q

what is the function of the outer ear?

A

capture sound and focus it on tympanic membrane
amplify frequencies by resonance in canal
protect ear from external threats

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3
Q

what does the outer ear consist of?

A

Pinna

external auditory canal

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4
Q

where does the middle ear start?

A

at tympanic membrane

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5
Q

what is the function of the middle ear?

A

amplifies sound by focusing vibrations

using leverage from incus-stapes joint to increase force on oval window

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6
Q

how does the middle ear focus vibrations?

A

large surface area of tympanic membrane to small surface area of oval window, therefore increases pressure

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7
Q

what is the role of the cochlea?

A

hearing part of inner ear
transduces vibration to nervous impulses
produces frequency and intensity analysis of sound

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8
Q

what are the compartments of the cochlea?

A

scala vestibuli, scala media and scala tympani

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9
Q

what are the scala vestibuli and scala tympani?

A

bony compartments of cochlea, contain perilymph (high in Na+)

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10
Q

what is the scala media?

A

membranous compartment of cochlea, contains endolymph

is the hearing organ/organ of corti

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11
Q

what is the basilar membrane?

A

base of the organ of corti

contains sensory receptors for hearing along its length which are arranged tonotopically

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12
Q

what is the function of the external auditory meatus?

A

guides sound waves to tympanic membrane

ceruminous glands secrete ear wax (cerumen) to trap foreign objects

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13
Q

what is the tympanic membrane?

A

ear drum

thin connective tissue membrane covered by skin externally and a mucous membrane internally

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14
Q

what are auditory ossicles?

A

transmit vibration of tympanic membrane to oval window

Malleus, incus, stapes and stapedius, tensor trympani

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15
Q

what is the malleus?

A

bone connected to tympanic membrane and incus

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16
Q

what is the incus?

A

connects malleus and stapes

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17
Q

what is the stapes?

A

footplate inserts onto oval window, connects middle and inner ear

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18
Q

what are the stapedius and tensor tympani?

A

skeletal muscles attached to auditory ossicles

protect ear from prolonged, loud but not explosive sounds

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19
Q

what is the eustachian/pharyngotympanic tube?

A

canal linking middle ear and nasopharynx
equalises middle ear pressure
but pathogens may travel through tube

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20
Q

what is the organ of corti?

A

hearing organ
contains inner and outer hair cells
allows transduction and modulation of sensitivity of sound

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21
Q

what is the arrangement of inner and outer hair cells in the organ of corti?

A

one row of inner hair cell to 3 rows of outer hair cells

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22
Q

what is the role of inner hair cells?

A

carry afferent information to auditory nerve

therefore transduction of sound

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23
Q

what is the role of outer hair cells?

A

modulate sensitivity of response to sound
because they carry efferents to auditory nerve
in contact with tectorial membrane above hair cells unlike IHCs
contraction of OHCs moves tectorial membrane

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24
Q

what are hair cells?

A

cells within organ of corti with stereocilia (hairs) which are able to deflect

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25
describe the process of transduction in the organ of corti?
deflection of stereocilia towards the longest cilium (kinocilium) opens K+ channels depolarises the cell, neurotransmitter released (glutamate) higher amplitudes cause greater deflection and more K+ channel opening hyperpolarisation closes K+ channels
26
what is the auditory pathway?
spinal ganglia from cochlea go via VESTIBULOCOCHLEAR nerve CN VIII to ipsilateral cochlear nuclei crosses at superior olive level, connections are now bilateral travels to inferior colliculus in the brainstem then medial geniculate body in thalamus enters temporal lobe auditory cortex or goes to lanuage centre
27
how is the primary auditory complex arranged?
tonotopically - small to large frequencies (pitch) rostral to caudally
28
what is frequency of sound?
pitch in Hz | cycles per second
29
what is sound amplitude?
volume in dB | sound pressure
30
what are the frequency and volume ranges for humans?
20-20,000Hz | 0dB-120dB
31
name every type of hearing assessment
``` tuning fork (weber, rinne test) pure tone audiometry central processing assessment tympanometry otoacoustic emissions auditory evoked potentials auditory brainstem response cortical potentials ```
32
what is the weber test?
tuning fork placed on top of head (should hear on both sides) tests for unilateral hearing loss conductive - heard louder in deaf ear sensorineural - heard louder in normal ear
33
what is the rinne test?
tuning fork test compares air conduction vs bone conduction in each ear detects unilateral hearing loss positive - normal, air louder than bone negative - bone louder than ear, conductive false positive - air louder than bone, sensorineural
34
what is pure tone audiometry?
measures hearing acuity for variations in sound intensity an frequency produces an audiogram where hearing thresholds are plotted
35
what is a central processing assessment?
assessments of hearing abilities other than detection e.g localisationm, speech in noise, filtered speech verbal and non verbal tests
36
what is tympanometry?
examination to test middle ear and mobility of tympanic membrane and conduction bones (ossicles)
37
what is otoacoustic emissions test?
newborn hearing screening and hearing loss monitoring test | OAEs produced by outer hair cells are detected
38
what are auditory evoked potentials?
records time it takes nerves in the auditory system to respond to sound and electrical stimulation evoked by clicks or tone bursts
39
what is auditory brainstem response ABR?
measures electrical activity from 8th nerve and brainstem nuclei/tracts evoked by clicks
40
why are cortical potentials measured?
not widely used | neurological or processing disorders may affect them
41
what are the types of hearing loss?
conductive sensorineural mixed
42
what is conductive hearing loss?
outer/middle ear problems
43
what is sensorineural hearing loss?
problem located in inner ear or auditory nerve
44
what is mixed hearing loss?
conduction and transduction of sound affected | more than one part of ear affected
45
how is hearing loss quantified?
mild moderate severe profound
46
what are the causes of conductive hearing loss?
outer ear - wax, foreign body | middle ear - otitis, otosclerosis
47
what are the causes of sensorineural hearing loss?
inner ear - presbycusis, ototoxicity | nerve - VIII nerve tumour
48
how is hearing loss treated?
based on underlying cause - hearing aids - brainstem implants - cochlear implants
49
what are hearing aids?
amplify sound without replacing any structure | are made to measure for certain frequencies and are dependent on cell preservation
50
what are cochlear implants?
replaces hair cell function receives, transmits, analyses and transforms sound to electrical impulses needs functioning auditory nerve to work
51
what are brainstem implants?
suitable when auditory nerves are damaged | electrical signals sent to set of electrodes placed in brainstem, aiming for cochlear nucleus
52
what inputs does the vestibular system compose of?
visual (eye), proprioceptive (pressure) and vestibular information
53
what outputs does the vestibular system have?
mainly reflexes - postural control, ocular reflex | nausea
54
where is the vestibule located?
in inner ear, connected to cochlea | deeper into head than cochlea
55
what is the structure of the vestibule?
utricle and saccule
56
what does the vestibular organ consist of?
utricle, saccule and semicircular canals
57
what is the structure of a vestibular hair cell?
stereocilia and a kinocilia (largest cilia)
58
what are the otolith organs?
utricle and saccule | cells are located on the maculae, placed horizontally in the utricle and vertically in the saccule
59
what is the maculae?
part of utricle and saccule that detects linear acceleration contain hair cells, gelatinous matrix and otolith crystals on top to aid hair deflection orientation - vertical = saccule horizontal = utricle
60
what connects the utricle and the semicircular canals?
ampullae
61
what is the structure of the ampulla?
crista where hair cells are located, surrounded by cupula which helps hair cell movements
62
how do hair cells detect head movement?
gravity deflects calcium carbonate crystals, causing stereocilia to bend towards kinocilia, depolarisation occurs, increasing hair cell firing rate from basal level OR gravity deflects calcium carbonate crystals, causing stereocilia to bend away from kinocilia, hyperpolarisation occurs, decreasing hair cell firing rate from basal level
63
what sort of movement/acceleration does the utricle detect?
horizontal movement
64
what sort of movement/acceleration does the saccule detect?
vertical movement
65
what sort of movement/acceleration do the semicircular canals detect?
angular, canals work in pairs cupulla moves and displaces hair cells output signal on VIII nerve is velocity
66
what are the vestibular output/reflexes?
vestibulo-ocular reflex | vestibulo-spinal reflex
67
what is the vestibuloocular reflex?
keeps images fixed in retina connection between vestibular nuclei and oculomotor nuclei - eye movement in opposite direction to head but with same velocity and direction
68
what is the vestibulospinal reflex?
maintains postural control by compensatory body movement according to head position motor neurons to limb muscles (lateral tract) or neck/back muscles (medial tract)
69
how is the vestibular system function assessed?
posture and gait cerebellar function eye movements all via vestibular tests, imaging and history taking
70
what are the vestibular tests?
caloric test video head impulse test vestibular evoked myogenic potential rotational test
71
what are peripheral vestibular disorders?
labyrinth or VIII nerve dysfunction aka menieres, BPPV, vestibular neuritis, unilateral/bilateral vestibular hypofunction
72
what are central vestibular disorders?
CNS brainstem/cerebellum dysfunction aka stroke, MS, tumour
73
which vestibular diseases have acute presentation?
vestibular neuritis | stroke
74
which vestibular diseases have intermittent presentations?
benign paroxysmal positional vertigo
75
which vestibular diseases have recurrent presentations?
menieres disease | migraines
76
which vestibular diseases have progressive presentations?
schwannoma of VIII | degenerative conditions e.g MS
77
what is BPPV?
crystals displaced from utricle into semi circular canals causing nystagmus and nausea upon certain head movements
78
what is meniere's disease?
hearing and balance issues due to malabsorption of endolymph
79
describe the vestibular ocular reflex when turning head to the right
right lateral canal stimulated (otolith movement) and left lateral canal inhibited (hyperpolarised) stimulates right vestibular nucleus, inhibits left vestibular nucleus left abducens nucleus stimulated, right abducens inhibited right oculomotor nucleus stimulated, left oculomotor nucleus inhibited therefore right medial rectus will contract and left lateral rectus will contract eye moves in opposite direction to head tilt simply - vestib and oculomotor on side turning towards are stimulated, abducens inhibited and opposite on other side
80
what area in the brain may be associated with cerebral control of vestibular system?
parieto-insular vestibular cortex
81
interpretation of Webers test
If a patient has a unilateral CONDUCTIVE hearing loss, the tuning fork sound will be heard louder in the deaf ear. If a patient has a unilateral SENSORINEURAL hearing loss, the tuning fork sound will be heard louder in the normal ear. In bilateral and symmetrical hearing loss of either type Weber’s test will be normal.

BRS Year 2 (67 decks)

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