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Neuro Test 3 > physiology of auditory and vestibular systems > Flashcards

physiology of auditory and vestibular systems Flashcards

1
Q

auditory system

A

detects sound and uses acoustic cues to ID and locate sound sources in the environment

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2
Q

sound

A

oscillations of air pressure that vary rapidly with time

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3
Q

amplitude

A

sound pressure (intensity) specified by a scale of sound pressure level (SPL) in decibels (dB)

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4
Q

frequency

A

number of oscillations of air pressure per second (Hz)

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5
Q

endolymph

A

potassium-RICH fluid filling cochlear duct and the membranous labyrinth; bathes apical end of hair cells

  • similar to intracellular fluid: high in [K+] low in [Na+]
  • found in scala media
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6
Q

perilymph

A

potassium-POOR fluid that bathes basal end of cochlear hair cells

  • similar to ECF: high [Na+] and low [K+]
  • found in scala vestibuli and scala tympani
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7
Q

central axons from the primary auditory neurons of the spiral ganglion project to the brainstem via the _____

A

auditory nerve (part of CN VIII)

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8
Q

basilar membrane

A

allows conversion of pressure waves from ossicles

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9
Q

Which side of the basilar membrane is higher frequencies? How much movement?

A

base

maximal

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10
Q

Which side of the basilar membrane is lower frequencies? How much movement?

A

apex

minimal

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11
Q

What direction does the sound wave travel in the basilar membrane?

A

base of the cochlea to the apex

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12
Q

What is the base of the basilar membrane near?

A

oval window

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13
Q

What is the apex of the basilar membrane near?

A

helicotrema

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14
Q

What are the properties of the basilar membrane near the oval window?

A

narrow and stiff

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15
Q

What are the properties of the basilar membrane near helicotrema?

A

wider and more bendy

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16
Q

hair cells are ___

A
  • mechanoreceptors
  • specialized polarized epithelial cells
  • basal and apical ends
  • stereocilia on apical surface
  • stiff, graded in size, rich in actin
  • neural synapses on basal side
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17
Q

kinocilium

A

tallest cilia next to the second tallest stereocilia

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18
Q

What happens when stereocilia are deflected toward kinocilium?

A

-K+ ions from endolymph enters hair cell to depolarize it

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19
Q

What are the 2 factors driving electrochemical gradient?

A
  • large endolymphatic potential (K+ gradient)

- large electrical gradient (scala media has high positive charge)

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20
Q

What happens when K+ enters a hair cell?

A
  • opening of voltage-gated Ca2+ channels
  • Ca2+ enters cell
  • vesicle-membrane fusion
  • excitatory NT released
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21
Q

Are stereocilia connected? If so, by what?

A

YES, chains called tip links, ankle links, and kinociliary links

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22
Q

What is the result of stereocilia reflection?

A

toward kinocilium = depolarization –> release of glutamate and generation of APs
away from kinocilium = hyperpolarization = inhibition

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23
Q

TRPA1

A

mechanically gated K+ ion channel on hair cells

24
Q

stria vascularis

A

component of the scala media that maintains electrochemical properties of the endolymph

25
Q

inner hair cells

A

single row

  • primary source of auditory information
  • afferents - neuron from inner hair cell to brain stem (type 1 afferent neuron)
26
Q

outer hair cells

A
  • 3 rows
  • act as amplifier
  • contractile (prestin)
  • boost mechanical vibrations of the basilar membrane
  • sensitivity and tuning of responses are susceptible to injury of outer hair cells
  • otoacoustic emissions
  • afferents - single neuron from multiple outer hair cells to brain stem (type II afferent neurons)
  • efferents - single neuron from brain stem to multiple outer hair cells
27
Q

Where are hair cells positioned?

A

along the length of the cochear spiral

28
Q

Where do hair cells receive afferent innervation from?

A

spiral ganglia

29
Q

Where do hair cells receive efferent innervation from?

A

superior olivary complex

30
Q

What does the cochlear nerve branch to?

A

cochlear nuclear complex in the medulla - VCN and DCN

31
Q

DCN

A

dorsal cochlear nuclei

-integrates acoustic information with somatosensory information for LOCALIZATION of sound

32
Q

VCN

A

ventral cochlear nuclei

-begins processing the temporal and spectral features of sound

33
Q

superior olivary complex

A
  • info from both ears converge=binaural processing
  • MSO = medial superior olivary nucleus - primary nucleus of superior olivary complex
  • tonotopic organization
  • receives excitatory (glutamate and/or aspartate) projections
34
Q

MSO function

A
  • interaural TIME differences to localize sound

- responds strongest when 2 inputs arrive simultaneously

35
Q

LSO function

A

-generates a map of the interaural INTENSITY differences to localize sound

36
Q

inferior colliculus function in hearing

A
  • suppresses info related to echoes

- estimates location along horizontal plane

37
Q

superior colliculus function in hearing

A

-takes localization from IC and adds vertical height to create a spatial map of the sound’s location

38
Q

medial geniculate nucleus (MGN)

A
  • thalamus
  • tonotopic map
  • convergence from distinct spectral and temporal pathways
  • processes speech inflections
39
Q

primary auditory cortex (AI)

A
  • conscious perception of sound
  • higher order processing of sound (loudness, modulations in volume, rate of frequency modulation)
  • tonotopic map maintained
  • rostral area - lower frequencies
  • caudal area - higher frequencies
40
Q

auditory (secondary) association cortex

A
  • multiple areas (Broca’s Wernicke’s)
  • less specifically organized in tonotopic arrangement
  • respond to more complex sounds (music), identifying (naming) a sound, and speech
41
Q

efferent input to the auditory system

A
  1. olivocochlear efferents
  2. middle ear muscle motoneurons
  3. autonomic innervation of the inner ear
42
Q

olivocochlear efferents

A
  • originate in superior olivary complex
  • medial OC neurons innervate outer hair cells
  • lateral OC neurons innervate inner hair cells
  • shifts responses to higher sound levels
  • decreases adaptation
  • reduces the response to noise
  • may protect hair cells from damage to intense sounds
43
Q

middle ear efferents

A
  • tensor tympani to the malleus (from CN V)
  • stapedius to the stapes (from CN VII)
  • bilateral response to high sound levels
  • contractions decrease transmission of sound
  • act at low frequncies
  • may prevent damage
  • may prevent low frequency masking (improving speech discrimination)
44
Q

otoacoustic emissions

A
  • ear emits sound, low intensity
  • spontaneous or evoked
  • spontaneous OAE in 1/3 of normal people in pure tones generated from motile outer hair cells
  • evoked emissions used to test for hearing loss (no emissions evoked if there is damage)
  • clinically important for newborn hearing screening, tinnitus, and ototoxicity
45
Q

sensorineural hearing loss

A
  • caused by damage to hair cells or nerve fibers or both
  • noise damage, ototoxic drugs, age related, loss of unknown etiology
  • OHCs are more susceptible to injury than IHCs
  • base (high frequency) end of cochlea is more susceptible to damage than apical (low frequency) end
  • injury to outer hair cells causes decrease in sensitivity (higher thresholds) and broader tuning
  • injury to inner hair cells cuts off auditory input to CNS
  • some hearing may be restored with a cochlear prosthesis
46
Q

cochlear prosthesis

A

multiple electrode array threaded through cochlea to stimulate surviving nerve fibers

47
Q

angular acceleration

A
  • spinning, turning
  • falling forward
  • falling backward
48
Q

linear acceleration

A
  • moving along a line (head’s point of view)
  • horizontally walking
  • vertically jumping
49
Q

utricle detects___

A

linear acceleration forward and backward

50
Q

saccule detects ____

A

linear acceleration up and down

51
Q

rotation in the horizontal plane is best detected by the ___

A

horizontal semicircular canal

52
Q

roatation in the vertical plane backward is best detected by the ___

A

posterior semicicular canal

53
Q

rotation in the vertical plane forward is best detected by the ____

A

anterior semicircular canal

54
Q

What eye muscles are activated when the horizontal semicircular canal is activated?

A
  • ipsilateral medial rectus m activated
  • ipsilateral lateral rectus m inhibited
  • contralateral lateral rectus m activated
  • contralateral medial rectus m inhibited
55
Q

What eye muscles are activated when the posterior semicircular canal is activated?

A
  • superior oblique m is activated

- inferior oblique m is inhibited

56
Q

What eye muscles are activated when the anterior semicircular canal is activated?

A
  • superior rectus m activated

- inferior rectus m inhibited

Neuro Test 3 (11 decks)

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