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Psych 330 > 27. ear > Flashcards

27. ear Flashcards

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1
Q

3 parts of outer ear?

A
  • pinna (ear shaped part)
  • auditory canal
  • tympanic membrane
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2
Q

4 parts of middle ear?

A

Ossicles (mini bones):
- malleus
- incus
- stapes
–> stapes hits oval window to transmit to cochlea

  • eustachian tube
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3
Q

2 Parts of inner ear?

A
  • Oval window
  • Cochlea
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4
Q

Why do we need the bones in the middle ear?

A
  • to amplify the vibrations that come from the auditory canal
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5
Q

Why do we need to amplify the vibrations?

A
  • the vibrations must be amplified in the middle ear because there is a density change from air to fluid in the inner ear
  • without the amplification (approx 30 dB), everything would be really muffled
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6
Q

What other structure helps with the amplification?

A

The tympanic membrane is 15-20x larger than the oval window, so sound energy is much more concentrated when it gets to cochlea

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7
Q

What are the 3 chambers of the cochlea? What 2 membranes separates them?

A
  • Vestibular canal
  • Cochlear duct
  • Tympanic canal

Reissner’s membrane separates Vestibular and Cochlear

Basilar membrane separates Cochlear and Tympanic

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8
Q

What are the 2 types of fluid that fill the cochlea? Which fluids are in which chambers?

A
  • perilymph
    –> vestibular canal
    –> tympanic canal
  • endolymph
    –> cochlear duct –> electrochemical properties that facilitate transduction

perilymph –> both the side ones
endolymph –> one important one

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9
Q

Basilar membrane def? What does it respond to? What does it do?

A
  • membrane between the walls of cochlea, separating cochlear duct and tympanic canal
  • thicker, narrower, and stiffer at BASE than at apex
  • each section responds most strongly to different frequencies
  • reflects the traveling sound waves in the perilymph
  • its displacement moves the hair hairs, which starts the process of transduction
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10
Q

Basilar membrane:
- characteristics from base to apex?
- frq most sensitive at each point?
- memory cue?

A

BASE:
- thicker, narrower, stiffer
- HIGHER frq

APEX:
- thinner, wider, floppier
- LOWER frq

Memory cues?
- uptight at the start, then loosens up a bit
- guitar strings –> the tighter (stiffer) they are, the more high frequency it will be
- the high will fade over time… :)

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11
Q

Characteristic frequency (of basilar membrane) def?

A
  • The frequency to which each location on the basilar membrane responds most readily
  • each location has a characteristic frequency, the frq it’s most sensitive to
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12
Q

Displacement envelope meaning? Which side is wider for high frq? Low frq?

A
  • the shape of the displacement of the basilar membrane from base to apex over time
  • higher frq –> wider by base
  • lower frq –> wider by apex
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13
Q

Organ of Corti:
- where is it located?
- what 3 important things does it consist of?

A
  • within the cochlear duct, resting on the basilar membrane

Consists of:
- inner hair cells
- outer hair cells
- tectorial membrane

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14
Q

Inner hair cells def / purpose?

A
  • Neurons in the organ of Corti
  • responsible for auditory transduction
  • connected to Type I nerve fibers
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15
Q

Outer hair cells def / purpose?

A
  • Neurons in the organ of Corti
  • serve to amplify and sharpen the responses of inner hair cells
  • connected to Type II nerve fibers
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16
Q

Tectorial membrane

A

A membrane that lies above the hair cells in the organ of Corti

17
Q

Auditory nerve def?

A
  • Conveys signals from the hair cells in the organ of Corti to the brain
  • made up of Type I and Type II auditory nerve fibers bundled together
18
Q

Tip links def? On what kind of cells? What do they do?

A
  • fibers that connect the top ends of adjacent cilia (hair cells)
  • BOTH types of hair cells
  • when the hair cells bend, the distance between them increases, and the tip links get really tense
  • this opens up membrane channels for potassium and calcium, causing depolarization
19
Q

Depolarization response in inner hair cells vs outer hair cells?

A

Inner:
- release NTs
- action potentials in Type I nerve fibers
- starts transductions

Outer:
- results in change of shape of proteins
- makes the cell and cilia stretch
- called motile response

20
Q

Motile response def? Relationship to activity on basilar membrane?

A
  • A response by outer hair cells that magnifies the movements of the basilar membrane, amplifying sounds and sharpening the response to particular frequencies
  • fine-tunes / specifies info from basilar membrane, especially for LOW frq
21
Q

What 2 ways is frequency represented on the basilar membrane?

A
  • place coding
  • temporal coding (timing)
22
Q

Place coding def?

A
  • Frequency representation based on the displacement of the basilar membrane at different locations
  • knowing where the max. displacement is can tell you what the frq is
23
Q

What did von Bekesy do?

A
  • discovered the physical basis for place coding
    –> ie. that the basilar membrane changes in stiffness, which determines its response to frequencies
  • he also determined envelopes of displacement
24
Q

Characteristic frequency (of type I nerve fiber) def? Accounted for by…?

A
  • the frequency to which the auditory nerve fiber is most sensitive
  • can be accounted for by the frequency tuning of the basilar membrane
25
Q

Frequency tuning curves for nerve fiber and basilar membrane. What does the graph show? What’s the important point? Why is this important?

A
  • shows the sound level (dB SPL) needed to produce a response in that nerve / location for each frequency
    –> generally higher as its farther away from characteristic frq
  • the lowest point is the characteristic frequency
  • the 2 curves directly mirror each other, which suggests that the tuning curve for the nerve fibers can be accounted for by the tuning curve for the basilar membrane
26
Q

Frequency tuning curves shape? Which direction?

A
  • they’re ASYMMETRIC
  • they extend more towards LOWER frequencies
  • ie. a nerve fiber will respond to a lot of frqs lower than its characteristic frequency, but not that many that are higher than its characteristic frq
27
Q

Frequency tuning curve: what shapes for lower and higher frequencies? What does this tell us?

A
  • lower frqs have much broader curves
  • higher frqs have much narrower curves
  • lower frequencies need more information from the outer hair cells to specify frq
28
Q

Relationship between tuning curves and masking effects?

A
  • tuning curves are ASYMMETRIC towards LOW frqs

Therefore…

  • masking effects extend MORE towards HIGHER frequencies
  • a low frq masks a high frq WELL
  • a high frq masks a low frq BADLY
29
Q

Temporal coding def? 2 ways?

A
  • frq representation based on firing rates of auditory nerve fibers
  1. firing matches frequency for some low frqs (up to a few hundred Hz)
  2. Phase synchronization (locking) extends the range (up to 4000-5000 Hz)
30
Q

Volley principle def? For what issue?

A
  • for phase synchronization with temporal coding for frequency
  • no cell can fire action potentials at every peak, but in a population, they can match the rate of the frequency
  • individual cells fire in phase with peaks of sound wave, but not at every peak

Book def:
- idea that each nerve fiber in a population of auditory nerve fibers produces action potentials in phase with the peaks in the incoming sound wave, even if not at every peak; explains how a temporal code could represent frequencies much higher than the maximum firing rate of any individual fiber

31
Q

How is amplitude represented / coded?

A
  • individual fibers are ambiguous
  • info ab amp comes from which nerves and how many are responding
  • look at frq tuning curves
  • if you know frq, and you know which ones are responding, you can determine a RANGE of amplitudes it could be
32
Q

How will a cells response to its characteristic frequency change with a change of amplitude?

A
  • for different nerves, their response to the characteristic frq VARIES with amplitude
  • if you have 2 nerves with the SAME ChFrq, but DIFFERENT thresholds and diff responses…
  • they’ll have a DIFFERENT firing rate at the SAME amplitude
  • so, you can know a range for the amplitude
33
Q

Dynamic range def? (for a nerve fiber)
What is it’s general shape? What are the two ends of the dynamic range called?

A
  • the range of amplitudes over which the firing rate of the fiber changes
  • generally an S shape
  • threshold at the beginning
    –> amp. where the nerve starts to fire above baseline
  • SATURATION LEVEL at the end
34
Q

Saturation level def?

A
  • the amplitude where a fiber reaches its MAXIMUM firing rate
  • no matter how loud the sound is, the fiber won’t fire any faster

Psych 330 (25 decks)

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