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Neuro Exam 3 > 2. Phys of Auditory & vision > Flashcards

2. Phys of Auditory & vision Flashcards

1
Q

what freq has a large deflection a narrow & stiff

A

high freq

near oval/round window

base of basilar mem

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2
Q

what freq has greatest deflection in the wider and more flexible region

A

lower freq

near helicotrema

apex of basilar mem

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3
Q

how is freq of sound (pitch) coded

A

along the basilar membrane there is the greatest deflection.

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4
Q

what does the auditory system do

A

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

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5
Q

what is sound

A

Oscillations of air pressure that vary rapidly with time.

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6
Q

what is amplitude

A

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

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7
Q

what is freq?

A

number of oscillations of air pressure per second (Hz).

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8
Q

where does wave propagate from

A

from base to apex

until point of maximal displacement occurs

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9
Q

how is tonotopy maintained in inner ear

A

high freq percieved in narrow/stiff (base of basilar mem)

& low freq in wider/flexible (apex of basilar mem

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10
Q

how is the pressure differential produced in cochlea

A

the cochlea is a closed-structure with one point of entrance and another point of exit for the dissipation of energy, the vibration of the basilar membrane

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11
Q

what does pressure differential cause

A

shearing force against stationary tectorial mem –> cause stereocilia of outer HC to be displaced

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12
Q

how are inner HCs activated

A

fluid movement in cochlear duct

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13
Q

how are stereocilia connected & what does movement cause

A

tip links that transmit force to elastic spring

–> open TRPA1 cells

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14
Q

what is the advantage of mechanotrandsuction

A

immediate effect -stimulated in 50 us

do not require receptor potential –> increase sensitivity

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15
Q

what is endolymph

A

the potassium-RICH fluid filling the cochlear duct & the membranous labyrinth;

bathes the apical end HCs.

  • Similar to the intracellular fluid (ICF): high in [K+] and low in [Na+].
  • Found in scala media
  • Produced by the stria vascularis
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16
Q

what is perilymph

A

the potassium-POOR fluid that bathes the basal end of the cochlear HCs.

  • Similar to the extracellular fluid (ECF): high [Na+] and low [K+].
  • Found in scala vestibuli and scala tympani
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17
Q

how are NTs released from HC

A
  • stereocilia bathed endolymph –> the opening of the cation channels cause a rapid influx of K+ into the cell –> HC depolarizes.
  • –> causes Ca2+ channels at the base of the cells to open. –> NT- filled vesicles fuse with the basilar mem and release NT (glutamate)
  • –> afferent cochlear nerve fibers stimulated & transmit this signal to the CNS.
18
Q

what occurs in upward displacement of basilar mem

A

Tips of the stereocilia on HCs embedded in the tectorial membrane, and the bodies of HCs rest on the basilar mem.

–> upward displacement basilar mem –> shearing force –> lateral displacement of the stereocilia –> depolarization of the hair cell.

19
Q

what occurs if there is a downward displacement of basilar mem

A

A downward displacement –> shearing force–> hyperpolarization of HCS

20
Q

what are the roles of inner & outer HCs

A

inner hair cells- hearing. ~ 90% of cochlear nerve fibers

outer hair cells - amplify the signals from inner hair cells.

21
Q

what is the role of stria vascularis

A

located in the lateral wall of the cochlear duct (scala media),

produces the endolymph with high levels of K+ (fills membranous labyrinth)

Stratified epithelial cells of SV extend cytoplasmic processes and folds around the capillaries of intraepithelial plexus –> K+ released from capillaries –> across tightly joined cells –> into the endolymph

22
Q

what are optimal conditions for HC depolarization? How is it maintained

A

endolymph with high [K+] maintained by stria vascularis

high endocochlear potential (+80 mV) –> drive K+ into HC down [] gradient.

the potential forms what is known as the blood-labyrinth barrier (BLB) = main sites of drug entry to access the inner HC

23
Q

organization of inner HCs

A
  • = primary source of auditory information
  • arranged in a single layer.
  • synapse with the peripheral terminal of a primary afferent sensory neuron
  • & efferent neuron modulates activity
24
Q

what do the outer hair cells do? and how to they do this

A
  • =amplify sound waves
  • = contractile –> boosts the mechanical vibrations of the basilar membrane
  • 3 rows
  • synapse with sensory afferent peripheral terminals from spiral ganglia & terminals from efferent ganglia
25
Q

what is otoacoustic emission

A
  • Motility of the outer HC –> basilar membrane & movement could be backward AKA toward the oval window and through the middle ear via the ossicles –> displacement of TM
  • result in the ear itself producing a sound ==> this can be measured in the external auditory meatus as otoacoustic emissions (OAE).
    1. Originate in the superior olivary complex.
    2. Known as olivocochlear efferents
    3. Medial olivary complex neurons innervate outer hair cells
    4. Lateral olivary complex neurons innervate inner hair cells
26
Q

what does OAE testing measure

A

measures absence of sound waves by the cochlear outer HCs in response to sound stimuli

A microphone at the external ear canal detects the low-intensity OAEs (evaluates hearing from middle ear to outer hair cells–>used to screen for sensorineural hearing loss but cannot detect auditory neuropathy)

27
Q

what do Olivocochlear efferents do

A
  • Reduces electromotility of outer hair cells.
  • Decreases basilar membrane motion
  • Reduces responses of inner hair cells and auditory nerve fibers
28
Q

what do Medial ear efferents do

A
  • Attenuates sound.
    • Tensor tympani to the malleus and the tympanic membrane
    • Stapedius to the stapes (from CN VII).
  • Bilateral response to high sound levels.
  • Contractions decrease transmission of sound.
  • Act at low frequencies.
  • May prevent damage, low frequency masking (improving speech discrimination), HC from damage to intense sounds.
  • Implicated in tinnitus
29
Q

what do automatic efferents do

A
  • Arises from 8th cranial nerve
  • Sympathetic adrenergic fibers
  • Regulates vascular tone in blood supply to cochlea
30
Q

what is the fxn of dorsal & ventral cochlear nuclei

A

DCN= integrates the acoustic information with somatosensory information

VCN = Begins processing the temporal and spectral features of the sound.

31
Q

what do medial & lateral superior olivary complex do

A

-Receives glutamatergic (excitatory) input

MSO = a map of interaural TIME differences to help localization of sound.

LSO = amap of interaural INTENSITY differences to help localize the source of a sound.

Tonotopic map is maintained

32
Q

what is the function of inferior colliculus

A
  • suppresses information related to echoes, (that interferes with localization) and arrives at a final estimation of localization of sound along the horizon.
  • Information about time and intensity differences converge into the IC to help create a precise origin of sound location along the horizon.
  • Tonotopic map is maintained in IC.
33
Q

what does medial geniculate nucleus do

A
  • Part of the thalamus

Lots of convergence from distinct spectral and temporal pathways, allowing for processing features of speech inflections.

Precise information regarding intensity, frequency, and binaural properties of sound are integrated and relayed onward.

Tonotopic map is maintained.

34
Q

what is the fxn of primary auditory cortex (A1)

A

Essential in conscious perception of sound.

Higher order processing of sound (loudness, modulations in volume, rate of frequency modulation).

Tonotopic map is maintained.

35
Q

what is the secondary auditory association cortex (A2)

A

Less specifically organized in the tonotopic arrangement than the primary auditory cortex.

This is thought to respond to more complex sounds (music), identifying (naming) a sound, and speech.

36
Q

Anterior semicircular canal

A

Rotation in the vertical plane forwards maximally activates the anterior semicircular canal.

37
Q

horizontal semicircular canal

A

Rotation in the horizontal plane is best detected by the horizontal semicircular canal

38
Q

Posterior semicircular canal

A

Rotation in the vertical plane backwards maximally activates the posterior semicircular canal.

39
Q

utricle

A

detects linear acceleration forward and backward.

40
Q

saccule

A

linear acceleration up & down

41
Q

how does cochlear prosthesis work

A

proble with HC or cochlear N

implant - external & internal component

internal component = receiver - decode signal & deliver electrical signal & electrode array - inserted into cochlea thru oval window & sits in cochlear duct along afferent CN 8 –> electical signal stimulate cochlear N alone basilar men

array - mimic tonotopy

Neuro Exam 3 (16 decks)

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