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Psych 330 > 27. ear > Flashcards

27. ear Flashcards

(34 cards)

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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

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A

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

17
Q

Auditory nerve def?

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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?

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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?

Study These Flashcards
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?

Study These Flashcards
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?

Study These Flashcards
A
  • place coding
  • temporal coding (timing)
22
Q

Place coding def?

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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?

Study These Flashcards
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…?

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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
Frequency tuning curves for nerve fiber and basilar membrane. What does the graph show? What's the important point? Why is this important?
- 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
Frequency tuning curves shape? Which direction?
- 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
Frequency tuning curve: what shapes for lower and higher frequencies? What does this tell us?
- 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
Relationship between tuning curves and masking effects?
- 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
Temporal coding def? 2 ways?
- 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
Volley principle def? For what issue?
- 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
How is amplitude represented / coded?
- 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
How will a cells response to its characteristic frequency change with a change of amplitude?
- 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
Dynamic range def? (for a nerve fiber) What is it's general shape? What are the two _ends_ of the dynamic range called?
- 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
Saturation level def?
- 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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