Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

neuro > 1B auditory and vestibular systems > Flashcards

1B auditory and vestibular systems Flashcards

1
Q

How many sections is the ear divided into?

A
  • Outer ear
  • Middle ear
  • Inner ear
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where is the ear embedded in?

A

The petrous portion of the temporal bone- the hardest bone in the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What makes up the outer ear?

A

The pinna and the external auditory canal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the outer ear’s functions?

A
  • To capture sound and to focus it on the tympanic membrane (ear drum- this is in the middle ear)
  • To amplify some frequencies by resonance in the canal
  • To protect the ear from external threats by the hairs lining it and wax
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the two main functions of wax?

A
  • Physical: protects the hair from external threats by capturing things
  • Chemical: pH should destroy at least some pathogens that enter ear
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What makes up the middle ear?

A

Starts at the tympanic membrane and has the tympanic area in it with the ossicles and stapedius muscle etc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the functions of the middle ear?

A

The main purpose overall is amplification of sound and transmission of it into the oval window to go into the inner ear

  • Focussing vibrations from a large surface area (tympanic membrane) to a smaller surface area (oval window)- the change in surface area means the pressure is increased
  • Using leverage from the incus-stapes joint to increase the force on the oval window (to amplify the sound)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What makes up the inner ear?

A

The hearing part of the inner ear is the cochlea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the function of the cochlea?

A
  • To transduce vibration into nervous impulses
  • While doing so, it also produces a frequency (pitch) and intensity (loudness) analysis of the sound
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What compartments is the cochlea divided into and describe them?

A
  • The scala vestibuli, scala media and scala tympani
  • Scala vestibuli and tympani are 2 bone structures that are joined up and contain perilymph- this is high in sodium
  • Scala media- a membranous structure in between vestibuli and tympani that contains endolymph- this is high in potassium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What lies in the scala media?

A

The hearing organ (Organ of Corti)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the basilar membrane and what’s special about it to its function?

A
  • The basilar membrane is the structure where the organ of Corti lies
  • It’s arranged tonotopically (same principle as a xylophone) where at the base it’s thicker, narrow and tight and at the apex further along it’s thinner, wide and looser
  • This means it’s sensitive to different frequencies at different points along its length
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What would happen to high freq vs low freq sounds in the basilar membrane?

A
  • High frequency sounds lead to the thicker base moving more than the apex, meaning the cells in the base will be participating more in the transduction of that sound
  • Low frequency sounds lead to the thinner apex moving more than the base, meaning the cells in the apex will be participating more in the transduction of that sound
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does the organ of Corti contain that helps it in transduction of sound?

A

Thousands of hair cells- inner hair cells (IHC) and outer hair cells (OHC)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How many columns are IHC vs OHC arranged in?

A
  • IHC are arranged in one column
  • OHC are arranged in 3 columns
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does the tectorial membrane do?

A
  • It’s located above the hair cells and will allow hair deflection- this depolarises the cell
  • Only OHC hairs are in constant contact with the tectorial membrane, and these assist the contact with the IHC
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the function of IHC?

A

Their function is the transduction of the sound into nerve impulses

  • Carry 95% of afferent info of the auditory nerve
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the function of OHC?

A

Function is modulation of the sensitivity of the response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How do OHCs modulate the sensitivity of response?

A

OHCs have a protein in their membrane to allow the cell to contract and change length to make the tectorial membrane closer or further from the IHC- if it’s closer then the IHC will transduce the sound but if its further it won’t

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How does transduction work?

A
  • The hairs of the hair cells are called stereocilia
  • The deflection of the stereocilia towards the longest cilium will mechanically open up K+ channels
  • The ionic interchange depolarises the cell and the glutamate (or something in the same family) neurotransmitter is liberated and goes to the afferent nerve to cause an impulse
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What will higher amplitudes (louder sounds) do to the whole process?

A
  • Higher amplitudes will cause more vibration of the tympanic membrane, more vibration of ossicle chain
  • Generate more movement and pressure of endolymph and therefore more movement of basilar membrane so more cells will be stimulated
  • Tectorial membrane will come into contact with more cells which will help cause greater deflection of stereocilia and more K+ channel opening
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is active amplification by the OHC?

A
  • OHC are in charge of changing sensitivity of transduction to allow the IHC to transduce sounds
  • If sounds are too soft/quiet and mechanical movement of basilar membrane isn’t enough for IHC to touch the tectorial membrane, the OHC will contract and shorten themselves to bring the tectorial membrane closer to the IHC
  • If sounds are too loud, the OHC will elongate to push the tectorial membrane from the ICH hairs to not allow those cells to transduce all the sound, making it seem a bit quieter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Why is active amplification by the OHC important?

A
  • If this didn’t work, we would only be able to hear a narrow loudness range
  • A lot of normal sounds would be too quiet to hear and some loud noises, like cars, would be too loud and uncomfortable to hear
  • OHC are more commonly damaged during hearing loss
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the auditory nerve pathway like after the cochlea?

A
  • Spiral ganglions from each cochlea project via auditory vestibular nerve (VIII) to the ipsilateral cochlear nuclei (monoaural neurones)
  • Auditory info crosses at the superior olive level, but not all of it
  • After this point all connections are bilateral
  • Info then → inferior colliculus → medial geniculate body → auditory cortex in temporal lobe
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What does it mean that hearing is tonotopically organised?

A
  • The cochlea is tonotopically organised and this is reflected in nerve pathways
  • This is because there are different fibres innervating the basilar membrane from the apex to the base
  • Base nerve fibres will only transmit high frequencies and apex nerve fibres will only transmit low frequencies
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Why is it important to discriminate frequencies?

A

If we can’t we won’t be able to interpret speech

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is frequency/pitch (Hz)?

A

Cycles per second, perceived tone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is amplitude/loudness (dB)?

A
  • Sound pressure
  • Subjective attribute correlated with physical strength
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is human range of hearing for frequency and amplitude?

A
  • Frequency: 20Hz to 20,000Hz
  • Loudness: 0 dB to 120 dB sound pressure level (SPL)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Why is decibel scale a log scale?

A
  • Because the range of sensitivity is very large so it allows us to compress the scale on a graph
  • Reflects the fact that many physiological processes are non-linear (they can respond to both very low and very high values)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What happens to hearing acuity with age?

A
  • Decreases with age, particular with higher frequencies
  • Medium and low frequencies could be affected with the progression of hearing loss
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What are the types of hearing loss?

A
  • Conductive hearing loss
  • Sensorineural hearing loss
  • Central hearing loss
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is conductive hearing loss?

A
  • Problem in the outer or middle ear
  • Problem with sound getting into ear- cells are working fine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What does this audiogram show?

A

Conductive hearing loss

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is sensorineural hearing loss?

A

Problem is located in the inner ear or auditory nerve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What does this audiogram show?

A

Sensorineural hearing loss: bone and air conduction are together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What is central hearing loss?

A

Very rare; originates in brain and brainstem

38
Q

What are the causes of hearing loss in conductive hearing loss in the outer ear?

A
  • Wax
  • Foreign body
39
Q

What are the causes of hearing loss of conductive hearing loss in the middle ear?

A
  • Otitis
  • Otosclerosis
40
Q

What are the causes of hearing loss in sensioneural hearing loss in the inner ear?

A
  • Noise
  • Prebycusis- loss of hair with age
  • Ototoxicity- exposure to ototoxics like medication or drugs
41
Q

What are the causes of hearing loss in sensioneural hearing loss in the nerve?

A

Acoustic neuroma (vestibular schwannoma) (unilateral)

42
Q

What are the treatments for hearing loss?

A
  • Treating underlying cause e.g. clearing wax if it’s there
  • Hearing aids
  • Cochlear implants
  • Brainstem implants
43
Q

What do hearing aids do?

A
  • Amplify the sound but don’t replicate any structure
  • Depending on the hearing loss type, degree and characteristics of the patient there are many options e.g. could have just a high frequency hearing loss problem so get an aid just for that
  • Requires alive cells for this though
44
Q

What do cochlear implants do?

A
  • Replaces the function of the hair cells by receiving sound, analysing it, transforming it into electrical signals and sending an electrical impulse directly to the auditory nerve
  • It needs a functional auditory nerve to function but used in stead of dead cells
45
Q

What do brainstem implants do?

A
  • When the auditory nerves are affected structures, the electrical signals can be sent to a set of electrodes placed directly into the brainstem
  • It’s very risky, so it’s advised for people with bilateral important auditory nerve damage
  • If it’s unilateral, another option is usually advised
46
Q

What are the 3 main inputs of the vestibular system?

A
  • Visual info
  • Vestibular info (rotation and gravity)
  • Proprioceptive info (perception of where every part of your body is e.g. pressure on your feet when you’re standing)
47
Q

What are the outputs of the vestibular system?

A

Mainly reflexes to maintain a stable posture and stable gaze

e.g. if you lose balance, you want to gain it back quick

48
Q

What is the CNS’s role in the vestibular system?

A

Integrates info from inputs and generates the output responses

49
Q

Where is the vestibular organ?

A
  • In the posterior area of the inner ear
  • The inner ear contains hair cells for hearing and balance
50
Q

What parts is the vestibular organ split into?

A
  • Vestibule
  • Semicircular canals
51
Q

What makes up the vestibule?

A
  • Utricule and saccule
  • These are joined together by a conduit and the saccule is joined to the cochlea too
52
Q

Which semicircular canals are there in the vestibular organ?

A
  • 3 in each ear- anterior, posterior and lateral semicircular canals
  • They each have an ampulla on one side and are connected to the utricle
53
Q

What is the bony labyrinth?

A

The structure in the base of the skull where the vestibular system and cochlea are located

54
Q

What do the vestibular hair cells have coming off them?

A
  • Stereocilia
  • A kinocilium (the biggest cilium)
55
Q

What do the vestibular cilia do?

A

Allows the cell to depolarise with movement of the endolymph, generated by head movement

Depending on which direction the endolymph moves over the stereocilia and how big the movement is, this dictates the size and type of electrical impulse generated

56
Q

Where are vestibular cilia located in the vestibular system?

A

In all 5 organs:

  • Utricle
  • Saccule
  • Lateral semicircular canal
  • Anterior semicircular canal
  • Posterior semicircular canal
57
Q

What are otolith organs?

A
  • Utricle and saccule are the otolith organs
  • Their hair cells are located on the maculae, a gelatinous matrix with the otoliths on top
  • The maculae are placed horizontally in the utricle and vertically in the saccule
58
Q

Why are the utricle and saccule called the otolith organs?

A

They have carbonate crystals on top of the hair cells that help with the movement (deflection) of the hairs

59
Q

Where are the hair cells in the semicircular canals?

A
  • Are located in the ampulla- the rest of the canal only has endolymph, a liquid high in potassium
  • The ampulla has the crista where the hair cells are
60
Q

What surrounds the cilia in the semicircular canals?

A

The cupula, a gelatinous substance which the endolymph moves to help with hair cell movement

61
Q

What are the planes of the semicircular canals (SCC)?

A
  • The orientation of the canals in the head defines 3 planes
  • Anterior and posterior canals form a 90 degree angle
  • Lateral canals are horizontal to the other canals
62
Q

What are the pairs the SCC work in?

A
  • Both laterals
  • Anterior from one side and posterior from the other side and vice versa
63
Q

What is the nerve path from the vestibular nerve to the brain?

A
  • Primary afferents end in vestibular nuclei in the brainstem and in the cerebellum
  • The vestibular nuclei are the main generators of the vestibular reflexes
64
Q

Vestibular nuclei have projections to which areas and for which purposes?

A
  • Spinal cord- for postural changes
  • Nuclei of the extraocular muscles- for eye movement
  • Cerebellum- get feedback on if movement is coordinated
  • Centres for cardiovascular and respiratory control
65
Q

Where is the vestibular cortex thought to be and why?

A
  • There’s no one specific area- since many inputs and integrators are involved, many cortical areas participate e.g. motor, somatosensory, visual
  • Main processing centre thought to be in the parietal lobe, in the parieto-insular vestibular cortex (PIVC)
66
Q

What are the main 3 functions of the vestibular system?

A
  • To detect and inform about head movements
  • To keep images fixed in the retina during head movements
  • Postural control
67
Q

What are the 3 potentials the hair cells in the vestibular system have and when are they used?

A
  • Resting- hair cells have a resting potential which has a basal discharge to the nerve- this is to keep our posture upright when not moving (since forces like gravity are still acting)
  • Excitation- if e.g. the head moves, hair moves towards kinocilium and generates depolarisation and an increase in nerve discharge
  • Inhibition- if one ear is being depolarised, the other ear’s vestibular system will be inhibited- the hair moves away from kinocilium and generates hyperpolarisation and a reduction in nerve discharge
68
Q

What kind of acceleration do the otolith organs deal with?

A
  • Linear acceleration and tilt e.g. horizontal movement and vertical movement in one plane
  • e.g. below when upright the otoliths have a resting potential so the head and neck muscles are contracted/relaxed to keep head in that position
  • When moving or tilting head backwards and forwards, the otoliths read this and allow for compensatory movements e.g. if head is tilting back we can snap it forward
69
Q

Out of utricle and saccule, which is responsible for sensing which kind of movement out of horizontal and vertical?

A
  • Utricle- horizontal movement
  • Saccule- vertical movement
70
Q

What kind of acceleration do the semicircular canals deal with?

A
  • Angular acceleration
  • The cupula moves and displaces hair cells
  • During angular movement of head, one side’s vestibular system would report depolarisation and other’s would report hyperpolarisation and both info will go to brainstem and be integrated to see which direction the head is moving in and its acceleration
71
Q

What are the 2 vestibular reflexes to know?

A
  • Vestibulo-ocular reflex (VOR)
  • Vestibulo-spinal reflex (VSR)
72
Q

What does the VOR do?

A
  • Keeps images fixed in the retina
  • It’s the connection between the vestibular nuclei and oculumotor nuclei
  • It allows for eye movement in the opposite direction to head movement with the same velocity and amplitude
  • It’s like staring at a dot and moving the head around but the dot stays fixed in our eyesight
73
Q

What are the main symptoms of a balance disorder?

A
  • Vertigo
  • Dizziness
74
Q

What is vertigo?

A

Perception of rotation: seeing things spinning around

75
Q

What is dizziness?

A
  • Related to vertigo but not necessarily a spinning sensation
  • More of a loose term e.g. some have blurred vision, some have nausea, some have vertigo and all may call it dizziness- have to dig deeper as a doctor if a patient says they’re dizzy
76
Q

What can balance disorders be categorised based on?

A

Based on location of affected structure and evolution of signs

77
Q

What types of balance disorders are there based on location of affected structure?

A
  • Central vestibular disorders
  • Peripheral vestibular disorders: Labyrinth and/or VIII nerve before it goes into brainstem- more common than central disorders and are easier to manage
78
Q

What are some examples of peripheral vestibular disorders?

A
  • Vestibular neuritis
  • Benign paroxysmal positional vertigo (BPPV)
  • Meniere’s disease
79
Q

What is vestibular neuritis?

A

Inflammation of vestibular nerve

80
Q

What is BPPV?

A

Benign Paroxysmal Positional Vertigo

abnormal presence of otolith crystals in semi-circular canals that came from otolith organs and causes exaggerated movement of cupula when person stands up/lies down

81
Q

What is Meniere’s disease?

A

affects both hearing and vestibular system- is problem with absorption of endolymph, there’s more of it in inner ear that breaks membranes and causes intoxication of cells

82
Q

Give some examples of a central vestibular disorder

A
  • Stroke
  • MS
  • Tumours
83
Q

What types of balance disorders are there based on evolution of signs?

A
  • Acute: happens out of nowhere
  • Intermittent: comes and goes
  • Recurrent: comes in crises
  • Progressive: gets worse over time
84
Q

Give examples of balance disorders of acute evolution

A
  • Vestibular neuritis aka labyrinthitis
  • Stroke
85
Q

Give examples of balance disorders of intermittent evolution

A
  • BPPV
86
Q

Give examples of balance disorders of recurrent evolution

A
  • Meniere’s disease
  • Migraine
87
Q

Give examples of balance disorders of progressive evolution

A
  • 8th nerve schwannoma
  • Degenerative conditions (e.g. MS)
88
Q

If a patient comes in dizzy, other than vestibular problems, what else could it be?

A
  • Anaemia
  • Hypoglycaemia
  • Presyncopal episodes
  • Orthostatic hypotension
  • Heart disorders
  • Psychological
  • Gait disorders
89
Q

What is the HINTs exam?

A

Differentiate between peripheral and central causes of acute vertigo

  • HeadImpulseTest: Horizontal rotational VOR
    • VOR is preserved in central
    • No compensatory eye movement (catch-up saccade to refixate on target)
  • Nystagmus​: Vestibular organ Vs Cerebellar/brainstem nystagmus
    • Peripheral: horizontal, unidirectional, beats away from affected side
    • Stroke: vertical, bidirectional
  • TestofSkewDeviation: Verticalmisalignment - usually absent in peripheral pathology​
90
Q

What bedside tests are done for hearing assessment?

A
  • Whisper in ipsilateral ear whilst rubbing fingers in contralateral ear
  • Tuning Fork – 2 tests assess the presence of gross hearing loss.
  • Bedside tests are quick but not accurate

neuro (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions