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BRS YR2 > Auditory and Vestibular System > Flashcards

Auditory and Vestibular System Flashcards

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1
Q

What makes up the outer ear?

A
  • concha
  • external auditory meatus
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2
Q

What makes up the middle ear?

A
  • tympanic membrane
  • ossicles
  • tensor tympani
  • stapedius
  • oval window
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3
Q

What makes up the inner ear?

A
  • the vestibule
  • the semicircular canals
  • the cochlea.
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4
Q

What is the function of the inner ear?

A
  • transduction of sound into nervous impulses
  • captures frequency and loudness of sound
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5
Q

What is the function of the outer ear?

A
  • focuses sound on the tympanic membrane
  • modest amplification
  • protects ear from external threats
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6
Q

What is the function of the middle ear?

A
  • mechanical amplification of sound
  • can reduce amplitude of sound via contraction of the tensor tympani and stapedius muscles
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7
Q

What is the inner ear innervated by?

A

Vestibulocochlear nerve (CN VIII)

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8
Q

What is Transduction?

A
  • conversion of one energy form to another
  • mechanical sound waves to electrical signals
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9
Q

What is the auditory pathway in the ear?

A
  • stapes vibrates the oval window
  • perilymph in the scala vestibuli vibrates
  • waves in the perilymph move around the cochlea
  • the waves move into the perilymph in the scala tympani
  • the wave reaches the end at the round window
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10
Q

What is the auditory pathways to the brain?

A
  1. cochlea
  2. vestibulocochlear nerve
  3. dorsal or ventral cochlear nucleus
  4. inferior colliculus
  5. medial geniculate nucleus
  6. auditory cortex
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11
Q

What is the function of the inferior colliculus?

A

Localises sound so you know where it’s coming from

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12
Q

What is the pathway for signals in the dorsal cochlear nucleus?

A

Decussate to join the inferior colliculus

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13
Q

What is the pathway for signals from the ventral cochlear nucleus?

A
  • travels through superior olive on the same or opposite side
  • fibres travel to the inferior colliculus on the same side as the superior olive
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14
Q

Why is it rare to have total hearing loss after a stroke?

A

All connections after the superior olive are bilateral

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15
Q

What are the three ossicles?

A
  • malleus
  • incus
  • stapes
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16
Q

What are the three scala/compartments of the cochlea?

A
  • scala vestibuli
  • scala tympani
  • scala media
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17
Q

What is the structure of the cochlea?

A

Spiral tunnel

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18
Q

Decribe the three scala

A
  • scala vestibuli and scala tympani = bony sturctures containing perilymph
  • scala media = membranous structure containing endolymph
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19
Q

What is the difference between endolymph and perilymph?

A
  • perilymph = rich in Na+
  • endolymph = rich in K+
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20
Q

Where is sound tranduced into a nervous signal?

A

Organ of corti, located in the scala media

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21
Q

What does the organ of corti contain?

A
  • basilar membrane
  • inner and outer hair cells
  • tectorial membrane
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22
Q

What are the mechanical properties of the base of the basilar membrane?

A
  • narrow
  • short and stiff hair cells
  • detects high frequencies
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23
Q

What are the mechanical properties of the apex of the basilar membrane?

A
  • wide
  • long and loose hair cells
  • detects low frequencies
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24
Q

How are hair cells arranged in the organ of corti?

A

Three rows of outer hair cells to one row of inner hair cells

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25
What is the difference between the outer and inner hair cells?
- outer = efferents, modulate sensitvity of the response to sound - inner = afferents, transduce sound into nerve signals, most important for hearing
26
Describe the process of mechanotransduction
- vibration of the basilar membrane oscillates hair cells - stereoscilia sway with the same frequency as the basilar membrane - the oscillations **towards the longest cilia** change the structure of the membrane ion channels and cause changes in their permeability - K+ inlfux into hair cells leading to depolarisation - K+ channels close when stereocilia oscilate towards shortest cilia, leading to repolarisation
27
What are the longest cilia called?
Kinocilia
28
What are stereocilia?
- hairs on the hair cells cells which detect sound - located in the endolymph
29
What is the primary auditory cortex and how is it arranged?
- cortically processed sound - tonotopically organised like basilar membrane
30
What is the secondary auditory cortex?
Where association of sound occurs
31
Where are the auditory cortices located?
Temporal lobe
32
How can we categorise causes of hearing loss?
- sensorinueral - conductive
33
What is conductive hearing loss?
- ear connot transmit sound to cochlea due to mechanical problem - middle or outer ear affected - hair cells are functional when stimulated within the inner ear - 10% of hearing loss, often reversible
34
What is sensorineural hearing loss?
- both air and bone conduction are affected similarly - problem with the inner ear or vestibulocochlear nerve - sound is unable to be effectively transduced to the auditory cortex - 90% of hearing loss, often irreversible
35
What are possible causes of conductive hearing loss?
``` outer ear: - wax and foreign bodies middle ear: - otitis externa/media - otosclerosis (stuck stapes) ```
36
What are causes of sensorineural hearing loss?
- drugs - Meniere's disease - congenital infection - trauma - ageing
37
What are the main 2 tuning fork tests?
- Rinne's test - Weber test
38
What are the results for the Rinne's test?
- normal = air conduction > bone conduction - conductive HL = bone conduction > air conduction - sensorineural HL = normal
39
What are the results for the Weber test?
- normal = sound equal in both ears - conductive HL = sound louder in bad ear - sensorineural HL = sound louder in good ear
40
What is the function of the vestibular system?
- detect and inform about head movements - keep images fixed to the retina during head movements - balance
41
What are the main inputs of the Vestibular system?
Movement and gravity
42
What are the outputs of the Vestibular system?
- ocular reflex (maintains fixed image upon movement) - postural reflex (ensures individuals maintain composure)
43
What structure within the inner ear is anterior?
The cochlea concerned with auditory input.
44
Which nerve is involved in the vestibular system?
Vestibulocochlear nerve (CN VIII)
45
What structure within the inner ear is posterior?
- vestibular system labyrinth - contains bony, membranous and vestibular labyrinth
46
Where does the bony labyrinth lie?
Cavities in the petrous temporal bone
47
What is part of the vestibular organ?
- vestibular labyrinth (utricle and saccule), joined by a conduit. - Saccule is connected to the cochlea. - Three semi-circular canals (Anterior, posterior and lateral) in each ear. - ampulla on each side, connected to the utricle. - Canals contain endolymph fluid.
48
What angles are the semi-circular canals at?
- the anterior and posterior semi-circular canal form a 90-degree angle - lateral canals are horizontal to the other canals - therfore they work in pairs
49
What is the role of the stereocilia on the hair cells?
- orientated to a particular side - deflection induces cellular depolarisation in response to endolymph movement
50
What are the otolith organs?
- utricle - saccule
51
What is the function of the utricle?
- detects changes in horizontal acceleration - changes head position during neck flexion and extension
52
What is the function of the saccule?
- detects changes in vertical acceleration - changes head position during lateral tilt
53
How are cells arranged in the otolith organs?
- located in the maculae - horizontal in the utricle - vertical in the saccule
54
What is the maculae made up of?
- hair cells - gelatinous matrix (otolith crystals) - otoliths on top
55
What is in the ampulla?
- crista (hair cells) - cupula which facilitates hair cell movement
56
What does endolymph contain?
high concentration of K+
57
How does endolymph in the semilunar canals move upon rotation?
- moves in the opposite direction to rotation - exerts force on the cupula, causing it to fill and bend cilia - will either excite or inhibt cilia depending on the direction of rotation (towards or away from the cilia)
58
What should NOT be present in the semi-circular canals?
otoliths
59
Where does the vestibular nerve form nuclei?
- Oculomotor nucleus - Medial longitudinal fasciculus - Abducens nucleus - Vestibular nuclei (Main generator of reflex.) - Vestibular ganglion - Vestibulospinal tract
60
What does the vestibular nuclei have projections to?
- spinal cord - nuclei of the extraocular muscles - cerebellum - centres of cardiovascular and respiratory control
61
Where do the primary afferents of the vestibular nerve end?
vestibular nuclei in the brainstem
62
Where are the main processing centres of the vestibular cortex?
in the parieto-insular vestibular cortex (parietal lobe)
63
What is responsible for processing in the vestibular system?
- main: vestibular nuclear complex - adaptive: cerebellum
64
What happens with the stereocilia move towards the kinocilium?
- depolarisation - increasing nerve discharge - excitation
65
What happens with the stereocilia move away from the kinocilium?
- hyperpolarisation - reduced nerve discharge
66
What are the 2 different vestibular reflexes?
- vestibulo-ocular reflex - vestibulo-spinal reflex
67
What happens in the vestibulo-ocular reflex?
- eye movement in opposite direction to head movement (same velocity and amplitude) - impulse stimulates ipsilateral **vestibular nucleu**s then the contralateral abducens nucleus and then the ipsilateral **oculomotor nucleus** - contracts ipsilateral medial rectus and contralateral lateral rectus - keeps images fixed on the retina
68
How do acute unilateral vestibular disorders usually present?
- imbalance - dizziness - vertigo - nausea
69
How do slow unilateral and both bilateral vestibular disorders present?
- imbalance and nausea - no vertigo
70
How can vestibular disorders be characterised by location?
- peripheral (affects vestibular organ and/or vestibulocochlear nerve) - central (affects CNS, specifically brainstem/cerebellum)
71
What are some examples of peripheral vestibular disorders?
* Vestibular neuritis * Benign Paroxysmal Positional Vertigo (BPPV) * Meniere’s disease
72
What are some examples of central vestibular disorders?
- stroke - multiple sclerosis - tumours
73
What are the red flags for vestibular disorders?
* Headache * Gait problems * Hyper-acute onset * Hearing loss * Prolonged symptoms (>4 days)
74
How do you assess the vestibular system?
Assess eyes, ears and legs
75
What is the clinical exam for acute dizziness?
HINTS exam
76
What does the HINTS exam assess?
- Head Impulse test (horizontal rotation VOR) - Nystagmus (vestibular vs brainstem) - Test of Skew deviation (vertical misalignment)
77
How does Benign Paroxyxmal Positional Vertigo present?
intermittent vertigo when standing up which is resolved when sitting down, the duration about 30 seconds
78
How do you distinguish between BPPV and Meniere's disease?
in BPPV vertigo episodes are around 30 seconds long
79
What is the pathophysiology of BPPV?
Dislodging of carbonate crystals in the semi circular canals
80
What impacts the extent of the deflection of stereocilia and potassium ion channel opening?
amplitudes
81
What is frequency/pitch?
- Hz - cycles per second - perceived tone
82
What is amplitude/loudness?
- dB - sound pressure
83
What frequency is within the human range of hearing?
20-20,000Hz
84
What amplitude/loudness is within the human range of hearing?
0-120 dB
85
What decreases with age?
hearing acuity (especially at higher frequencies)
86
What is the role of a cochlear implant?
replaces the function of the hair cells by receiving sound, analysing it and transforming it into electrical impulses to the auditory nerve
87
What is required for a cochlear implant?
a functional auditory nerve
88
What can be used if the auditory nerve is not functional?
a brainstem implant
89
What is a brainstem implant?
electric signals from the cochlea can be relayed to a set of electrodes implanted directly into the brainstem
90
When is a brainstem implant advised?
patients with bilateral auditory nerve damage (high risk)
91
What do hearing aids do?
amplify sound (beyond hearing threshold of hearing loss)
92
What does the type of hearing aid depend on?
type, degree and characteristic of hearing loss
93
What are the possible treatments of hearing loss?
- hearing aids - cochlear implants - brainstem implants - underlying cause
94
What is the threshold for normal hearing?
0-20dB
95
What is the threshold for mild hearing loss?
20-40dB
96
What is the threshold for moderate hearing loss?
40-70dB
97
What is the threshold for severe hearing loss?
70-90dB
98
What is the threshold for profound hearing loss?
90+ dB
99
What is otitis media?
- inflammation of the middle ear - associated with infection
100
What is a characteristic of otitis media?
bubbles seen through the tympanic membrane
101
What is presbycusis?
progressive hearing loss due to age
102
What could affect cortical potentials?
- neurological conditions - processing problems
103
Why is a tuning fork used?
to establish the presence or absence of a hearing loss with a significant conductive component
104
What can the Rinne and Weber test do?
distinguish between conductive hearing loss and sensorineural hearing loss
105
What does the Rinne test do?
compares bone and air conduction
106
What does Otoacoustic emissions (OAEs) test?
- OAEs are produced by the outer hair cells as the expand and contract - none means the outer hair cells are NOT functional
107
What test is part of the new-born hearing screening and hearing loss monitoring?
Otoacoustic emissions (OAEs)
108
What is an audiogram?
where the hearing thresholds are plotted to define if there is a hearing loss or not
109
What is the difference between dizziness and vertigo?
- dizziness = room is still, you feel unstable - vertigo = room is spinning, you feel stable

BRS YR2 (67 decks)

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