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(OMS1) Neuro exam 3 > Physiology of Auditory and Vestibular systems > Flashcards

Physiology of Auditory and Vestibular systems Flashcards

1
Q

Where in the basilar membrane do high and low frequency (pitch) sounds get maximum deflection?

A

High - Base near the oval and round windows (narrow and stiff)
Low - apex near the helicostrema (wide and flexible)

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2
Q

Describe the tonotopy concept

A

Each sound wave is deflected at some point in the basilar membrane, depending on its frequency

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3
Q

Define the following
Sound
Amplitude
Frequency

A
  • air pressure oscillations
  • intensity of sound pressures (measured via dBs)
  • number of oscillations per second
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4
Q

Why is the vibration of the basilar membrane important?

A

Cochlea is a closed structure, so vibration of the basilar membrane will cause pressure change = force on tectorial membrane connected to the outer hair cell stereocilia tips = movement of stereocilia

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5
Q

What triggers the depolarization of hair cells?

A

Sterocilia moves > tip links connect them all > force on all the stereocilia > TRPA1 channels open

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6
Q

What type of channels are the TRPA1 channels? Why is this type important?

A

Mechanotransduction channels. Important because capable of rapid, immediate effects and very sensitive to stimuli since they don’t require receptor potentials

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7
Q

*What are the features of the endolymph?

A

Bathe the apical end of the hair cells
Rich in potassium, low in sodium (ICF like)
Found in scala media and made by the stria vascularis

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8
Q

What are the features of the perilymph?

A

Bathe the basal end of the hair cells
Low potassium, high sodium (ECF like)
Found in scala vestibuli and tympani

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9
Q

Describe the depolarization of the stereocilia

A

K+ rich in endolymph > TRPA1 opens and lets all this K+ into the hair cell = depolarization > Ca2+ entry releases the Glu vesicles > released at synapse on the cochlear nerve afferents > AP sent to CNS

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10
Q

What does upward and downward basilar displacement result in hair cells?

A 
Upward = lateral stereocilia displacement = depolarization
Downward = hyperpolarization
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11
Q

Why are inner hair cells important for hearing?

A

Most cochlear nerve afferents are from the inner hair cells and these need to be depolarized to get any hearing. Outer hair cells are amplifiers

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12
Q

Why is the stria vascularis important?

A

Has processes that wrap around the capillaries of a plexus. K+ is released from the capillaries into the endolymph and bathes the stereocilia. The presence of lots of K+ in the endolymph thanks to stria vascularis helps with depolarization (reaching the threshold positive potential of +80 mV)

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13
Q

What is the importance of the endocochlear potential?

A

+80 mV. Pretty positive and maintained by stria vascularis by letting the K+ from capillaries enter to reach depolarization threshold.

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14
Q

What happens when stria vascularis is compromised?

A

Endocochlear potential is lowered and there is less depolarization of the hair cells = hearing loss

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15
Q

What are the features of the inner hair cells?

A

Source of the auditory info
Arranged in single layer
Synapse at primary afferents at spiral ganglion

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16
Q

What are the features of the outer hair cells?

A

Amplifies sound info
Arranged in 3 rows
Synapse at primary afferents at spiral ganglion

17
Q

What are otoacoustic emissions?

A

Retrograde movement of the outer hair cells (from inner ear to TM) = ear itself produces sound

18
Q

Anatomical basis of the otoacoustic emissions

A

OAEs originate from the superior olive efferents (olivocochlear efferents). Medial olive neurons stimulate the outer hair cells while lateral olive neurons innervate inner hair cells.

19
Q

How are OAEs used for testing?

What can it and cannot test?

A
  • OAEs are generated in response to sound stimuli, so give patient sound stimuli and read the low intensity OAEs that come back as a response.
  • It can test sensorineural hearing loss but not auditory neuropathy
20
Q

What is the role of olivocochlear efferents in protecting the cochlea?

A

Prevents too much physical stimulation of the basilar membrane by controlling movement of inner and outer cell movements

21
Q

What is the role of middle ear efferents in protecting the cochlea?

A

Attenuates sound to avoid damage from TM to stapes (via contractions of tensor tympani (CN V) and stapedius (CN VII))
Damage to middle efferents = tinnitus

22
Q

What is the role of autonomic efferents in protecting the cochlea?

A

Regulates tone (constriction) of cochlear blood supply (via CN VIII)

23
Q

*Role of DCN vs role of VCN in auditory processing

A 
DCN = sound + somatosensory integration
VCN = begins processing sound features
24
Q

*Role of MSO vs LSO in auditory processing

A

Both receive glutamate input
MSO - time differences to localize sound
LSO - intensity differences to localize sound

25
Q

*Role of inferior colliculus in auditory processing

A

Suppresses info related to echoes since this interferes with localization
Time and intensity differences localize into IC to help localize origin of sound

26
Q

*Role of MGN in auditory processing

A

Info from features of sound converge here > processes features of sound > send to primary auditory cortex

27
Q

*Role of Primary auditory cortex in auditory processing

A

Conscious perception, higher order processing of sound

28
Q

*Role of secondary auditory association cortex in auditory processing

A

More complex sounds (music), identifying sound and speech

29
Q

How does a cochlear implant do and how does it work?

A

Help with sensorineural hearing loss due to hair cell or cochlear nerve damage.
Has a receiver and electrode array. EA is in the cochlea by the CN VIII afferents and stimulates a nerve fiber on the basilar membrane

30
Q 
What types of movement do these detect? 
Anterior semicircular canal
Horizontal semicircular canal
Posterior semicircular canal
Utricle
Saccule
A
  • falling forward
  • rotating around
  • falling backward
  • moving forward and backward
  • moving up and down

(OMS1) Neuro exam 3 (14 decks)

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