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BRS NEUROLOGY > 1b// The Auditory System > Flashcards

1b// The Auditory System Flashcards

1
Q

What do vestibular and hearing organs do?

A

Vestibular organ: capture low frequency motion (movements)

Hearing organ: capture high frequency motion (sound)

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2
Q

What cells do cochlea and canals come from?

A

stotocyst

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3
Q

What is frequency/ pitch (Hz)?

A

cycle per second, perceived tone

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4
Q

What is amplitude/ loudness (dB)?

A

Sound pressure, subjective attribute correlated with physical strength

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5
Q

What is the humans range of hearing?

A

Frequency: 20–20,000Hz

Loudness: 0 dB to 120 dB sound pressure level (SPL)

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6
Q

What are the outer ear functions?

A

To capture sound and to focus it to the tympanic membrane.

Modest amplification (10DB) of upper range of speech frequencies by resonance in the canal.

To protect the ear from external threats.

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7
Q

What is the function of the middle ear?

A

The main function of the middle ear is mechanical amplification (can provide an additional 20-30dB)

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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/ inner ear?

A

Its function is to transduce vibration into nervous impulses

It does so in a way that captures the frequency (or pitch) and intensity (or loudness) of the sound

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10
Q

How many compartments in the cochlea? And what are they?

A

3

scala vestibuli
scala tympani
scala media

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11
Q

What are the scala vestibuli and scala tympani?

A

Bone structures, contain perilymph (high in sodium)

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12
Q

What is the scala media?

A

Membranous structure, contains endolymph (high in potassium). Here is where the hearing organ or Organ of Corti is located.

*depending on frequency it will go through media at a certain point

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13
Q

What lies in the basilar membrane?

A

the organ of Corti

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14
Q

How is the basilar membrane arranged?

A

Basilar membrane is arranged tonotopically, using the same principle as a xylophone

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15
Q

What is the hearing organ?

A

the organ of corti

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16
Q

What does the organ of corti contain?

A

1) Inner hair cells (IHC) and
2) Outer hair cells (OHC)

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17
Q

What is above the hair cells?

A

tectorial membraine

18
Q

What does the tectorial membrane do?

A

allows hair deflection, which in turn will depolarise the cell.

19
Q

What do inner hair cells do?

A

IHC carry 95% of the afferent information of the auditory nerve. Their function is the transduction of the sound into nerve impulses.

20
Q

What do outer hair cells do?

A

OHC carry 95% of efferents of the auditory nerve. Their function is modulation of the sensitivity of the response.

21
Q

What are the hairs of the hair cells called?

A

stereocilia

22
Q

What is the longest stereocilia called?

A

kinocilium

23
Q

How do stereocilia work and what do they do?

A

The deflection of the stereocilia towards the longest cilium (kinocilium) will open K+ channels (influx of K+)= depolarisation

This depolarises the cell releasing the neurotransmitter to the afferent nerve which then depolarises.

Higher amplitudes (louder) of sound will cause greater deflection of stereocilia and K+ channel opening

AKA TRANSDUCTION

*away from kinocilium= hyperpolarisation

24
Q

WHat causes depolarisation and hyper-polarisation in transduction? (ion wise)

A

depolarisation= open K+
hyper= closes k+

25
Q

Describe the differences between IHC and OHC.
- arrangement
- contact with tectorial membrane
- carries what info
- function

A
26
Q

Describe the auditory pathways.

A

Spiral ganglions via the vestibulo-cochlear nerve (CN8) travel to the ipsilateral cochlear nuclei (monoaural neurons) in the brainstem (pons)

Auditory information crosses at the superior olive level

After this point all connections are bilateral

27
Q

What are the types of hearing loss?

A

conductive hearing loss
sensorineural hearing loss
central hearing loss

sudden or progressive hearing loss

28
Q

What is the difference between sudden and progressive hearing loss?

A

Sudden hearing loss minutes to days
Progressive hearing loss months to years

29
Q

What is conductive hearing loss?

A

problem is located in outer or middle ear

30
Q

What is sensorineural hearing loss?

A

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

90% of all hearing is lost

31
Q

What are causes of conductive hearing loss?

A

outer ear= wax, foreign body

middle ear= otitis, otosclerosis

32
Q

What is otitis?

A

Bubbles can be seen through the ear drum, suggesting there is liquid inside the middle ear.

due to inflammation/ infection (bac or viral)

33
Q

What can you use to see inside the ear?

A

otoscope

34
Q

What is otosclerosis?

A

formation of new bone around the base of the stapes

aka extra bone, it is progressive and common in young women

35
Q

What are causes of sensorineural hearing loss?

A

inner ear= noise, presbycusis, ototoxicity

nerve= acoustic neuroma (vestibular schwannoma) (unilateral)- can press on CN8

36
Q

What are clinical bedside tests for hearing?

A

whisper in ipsilateral ear whilst rubbing fingers in contralateral ear

tuning fork (weber and rinne test)= assesses the presence of gross hearing loss

37
Q

What is an audiogram? And what does hearing loss look like in one?

A

The audiogram is where the hearing thresholds are plotted to define if there is a hearing loss or not. A normal hearing threshold is located between 0 – 20dB

the decibels are going up to be heards headphones that make a clicking sound, can also put on mastoid

38
Q

What do conductive and sensorineural hearing loss look like in audiometry?

A

*normal for conductive hearing loss when its bone conduction

39
Q

What type of sound does the normal cochlea produce?

A

The normal cochlea produces low-intensity sounds called Otoacoustic Emissions (OAEs)

40
Q

What specific cells produce Otoacoustic emissions (OAEs) and when?

A

These sounds are produced specifically by the outer hair cells as they expand and contract

41
Q

How can hearing loss be monitored on new borns?

A

otoacoustic emissions (OAEs)

This test is often part of the newborn hearing screening and hearing loss monitoring.

42
Q

What is the treatment for hearing loss? (4)

A

underlying cause
cochlear implants
hearing aids
brianstem implants

BRS NEUROLOGY (22 decks)

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