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BRS Flashcards (Y2) > Auditory And Vestibular System > Flashcards

Auditory And Vestibular System Flashcards

1
Q

What type of frequency is captured by vestibular organs?

A

Low frequency motion (movements)

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2
Q

What type of frequency is captured by hearing organs?

A

High frequency motion (sound)

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3
Q

What comprises sound?

A

Frequency/pitch (Hz): Wave cycles per second - perceived tone
Amplitude/loudness (dB): Sound pressure - subjective attribute correlated with physical strength

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4
Q

What is the human range of hearing?

A

Frequency: 20-20,000Hz
Loudness. 0 dB to 120 dB sound pressure level (SPL)

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5
Q

What are the functions of the outer ear?

A

Capture sound and focus it to the tympanic membrane
Modest amplification (10dB) of upper range of speech frequencies due to resonance in canal
Protects the ear

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6
Q

What is the main function of the middle ear?

A

Mechanical amplification (20-30dB)
Useful for detecting low levels of sound

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7
Q

What are the functions of the tensor tympani and stapedius muscle?

A

Work to reduce sound (e.g. when things are too loud)
Tensor tympani contracts and stiffens tympanic membrane - reduces vibrations
Stapedius muscle contracts and stops stapes from vibrating as much

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8
Q

What is the hearing part of the inner ear?

A

Cochlea

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9
Q

What is the function of the cochlea?

A

Transduces vibration (through fluid) into nervous impulses
Able to capture frequency and intensity of the sound

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10
Q

Label this image

A
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11
Q

Label the image

A
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12
Q

What are the three compartment of the cochlea?

A

Scala vestibuli - bone
Scala tympani - bone
Scala media - membranous

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13
Q

What do the scala vestibuli and tympani contain and what is the substance high in?

A

Perilymph
High in sodium

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14
Q

What does the scala media contain and what is the substance high in?

A

Endolymph
High in potassium

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15
Q

Where is the hearing organ (Organ of Corti) located?

A

In the scala media of the cochlea

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16
Q

Does the Organ of Corti lie in the vestibular or basilar membrane?

A

Basilar

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17
Q

Describe the arrangement of the basilar membrane

A

Tonotopically arranged

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18
Q

What are the two types of hair cells of the organ of Corti?

A

Inner hair cells (arranged in one line)
Outer hair cells (arranged in lines of three)

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19
Q

What is the function of the tectorial membrane?

A

Located above hair cells
Allows deflection of hairs which leads to depolarisation of the cells

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20
Q

What is the function of the inner hair cells?

A

Carry 95% of the afferent information of the auditory nerve
Involved in transduction of sound into nerve impulses

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21
Q

What is the function of the outer hair cells?

A

Carry 95% of the efferent information of the auditory nerve
Involved in modulation of the sensitivity of the response

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22
Q

What is the name for the ‘hairs’ of the hair cell?

A

Stereocilia

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23
Q

Stereocilia deflect towards the what…?

A

Kinocilium (longest cilium)

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24
Q

What does deflection of the stereocilia cause?

A

Opens K+ channels
This depolarises the cell causing release of neurotransmitter to the afferent nerve which then depolarises

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25
Q

How are higher amplitudes of sound detected during transduction?

A

Higher amplitudes cause greater deflection of the stereocilia and K+ channel opening

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26
Q

Describe the auditory pathways

A

Spiral ganglions via the vestibulo-cochlear nerve travel to ipsilateral cochlear nuclei (monoaural neurons) in the pons
Auditory information crosses over at the superior olive level -> after this point all connections are bilateral

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27
Q

Where is the problem located with conductive hearing loss?

A

Outer or middle ear

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28
Q

Where is the problem located with sensorineural hearing loss?

A

Sensory organ (cochlear) or the nerve (auditory nerve)

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29
Q

What are the most and least common types of hearing loss?

A

Sensorineural - accounts for 90% of all hearing loss
Central hearing loss - very rare; originates in brain and brainstem

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30
Q

What is the difference between sudden and progressive hearing loss?

A

Sudden - minutes to days
Progressive - months to years

31
Q

What are some outer ear causes of conductive hearing loss?

A

Wax (cerumen impaction)
Foreign body

32
Q

What are some middle ear causes of conductive hearing loss?

A

Otitis - bubbles can be seen through ear drum suggesting presence of liquid inside the middle ear
Otosclerosis

33
Q

What are the inner ear causes of sensorineural hearing loss?

A

Noise
Presbycusis (old age)
Ototoxicity - e.g. chemotherapy or antibiotics (specifically gentamicin and other aminoglycosides, commonly given for UTIs in hospital)

34
Q

What are nerve causes of sensorineural hearing loss?

A

Acoustic neuroma/vestibular schwannoma - unilateral

35
Q

What does this image show?

A

Acoustic neuroma

36
Q

What are some clinical beside assessments for hearing?

A

Whisper in ipsilateral ear whilst rubbing fingers in contralateral ear
Tuning fork - two tests assess the presence of gross hearing loss - Weber and Rinne test

37
Q

Does hearing loss usually affect the whole frequency range?

A

No, tends to be frequency specific, e.g. high frequencies

38
Q

What is an audiogram?

A

Chart where hearing thresholds are plotted to define if there is hearing loss or not
Note: normal hearing threshold is located between 0-20dB

39
Q

Describe the defining thresholds for hearing loss in dB

A
40
Q

What type of hearing loss does each graph show?

A
41
Q

What are Otoacoustic Emission tests typically used in?

A

Newborn screening and hearing loss monitoring
Does not require a response - unlike audiometry

42
Q

How do Otoacoustic Emissions (OAEs) work?

A

Normal cochlea produces low-intensity sounds called OAEs
Sounds produced specifically by outer hair cells as they expand and contract
Sounds can be detected through a machine

43
Q

What are the treatments for hearing loss?

A

Treat underlying cause - e.g. infection
Hearing aids
Cochlear implants
Brainstem implants

44
Q

What are the inputs of the vestibular system and what detects them?

A

Movement and gravity
Detected by mechanical sensors

45
Q

What are the outputs of the vestibular system?

A

Ocular reflex
Postural control
Help maintain posture and gaze

46
Q

What components make up the vestibular organ?

A

Utricle and saccule (otoliths) are located in the vestibule and are joined to the cochlea (saccule is joined to the cochlea)
Three semicircular canals on each ear - anterior, posterior, lateral
Semicircular canals have an ampulla on one side and are connected to the utricle

47
Q

Label this image

A
48
Q

Where do the hair cells sit in the otolith organs?

A

In the maculae

49
Q

How are the maculae placed in the saccule and utricle organs?

A

Saccule - vertically
Utricle - horizontally

50
Q

What do the maculae contain?

A

Hairs cells
A gelatinous matrix
Otoliths on top - carbonate crystals that help the deflection of the hair cells

51
Q

What causes otolith movement?

A

Linear acceleration and tilt
Utricle - horizontal movement
Saccule - vertical movement

52
Q

Where are the hair cells of the semicircular canals located?

A

In the crista of the ampulla

53
Q

What surrounds the hair cells of the semicircular canals and what is the function of that structure?

A

Cupula - helps with hair cell movement

54
Q

Label this image

A
55
Q

The semicircular canals are high in what fluid?

A

Endolymph - high in potassium

56
Q

What kinds of movement do the semicircular canals detect?

A

Orientation of canals in the head defines three planes
Anterior and posterior canals form a 90 degree angle
Lateral canals are horizontal to the other canals
Work in pairs
Can detect movement at different angles - angular acceleration

57
Q

How are cells depolarised in the vestibular organ?

A

Hair cells have kinocilium and stereocilia
Movement of the endolymph causes deflection of cilia leading to depolarisation

58
Q

Describe hair cell potentials

A

Hair cells have a resting potential which has a basal discharge to the nerve
Movement towards kinocilium causes depolarisation- increase in nerve discharge
Movement away from kinocilium causes hyperpolarisation - reduction in nerve discharge

59
Q

Where do the primary afferent of the vestibular nerve end?

A

Vestibular nuclei of pons

60
Q

What other areas does the vestibular nerve communicate with?

A

Vestibulospinal tract
Abducens nucleus
Medial longitudinal fasciculus (connects 3rd and 6th nerve)
Oculomotor nucleus

61
Q

What are the key functions of the vestibular system?

A

Detect and inform about head movements
Keep images fixed in retina during head movements
Balance

62
Q

What is the vestibular-ocular reflex (VOR)?

A

Keeps images fixed in retina
Connection between vestibular nuclei and oculomotor nuclei
Eye movement in opposite direction to head movement, but same velocity and amplitude

63
Q

What is the purpose of the vestibulo-spinal reflex do?

A

Helps to maintain posture, e.g. when falling

64
Q

How do you categorise vestibular disorders?

A

Timing and laterality:
Acute and unilateral
- Main complaints are imbalance, dizziness, vertigo and nausea
Slow and unilateral or bilateral loss
- Main complaints are imbalance and nausea - no vertigo

65
Q

Give examples of peripheral vestibular disorders

A

Affect vestibular organ and/or VIII nerve:
Vestibular neuritis
Benign Paroxysmal Positional Vertigo (BPPV)
Meniere’s disease

66
Q

Give examples of central vestibular disorders

A

Stroke
Multiple sclerosis
Tumours

67
Q

What is the clinical approach to diagnosis of suspected vestibular disorders?

A
68
Q

What is it called when the eyes change in the laterality of how they move?

A

Skew

69
Q

Name two acute balance disorders

A

Vestibular neuritis
Stroke

HINTS exam useful to differentiate

70
Q

Name an intermittent balance disorder

A

Benign Paroxysmal Positional Vertigo

Dix-Hallpike Test - useful in diagnosis

71
Q

Name a recurrent balance disorder

A

Migraine ( Meniere’s disease)

72
Q

Name two progressive balance disorders

A

Schwannoma vestibular (VIIIth nerve)
Degenerative conditions (MS)

73
Q

Describe the steps of the HINTS exam

A

Head Impulse test
- Horizontal rotational VOR
Nystagmus
- Vestibular organ vs cerebellar/brainstem nystagmus
Test of Skew deviation
- Vertical misalignment - usually absent in peripheral pathology

BRS Flashcards (Y2) (79 decks)

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