Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Audition II > Unit 1 - Lecture 2 > Flashcards

Unit 1 - Lecture 2 Flashcards

1
Q

What are the details of the travelling wave? Effect of sound level on what?

A
  • Bekes’y early finding
  • Modern tech and active component
  • Effect of sound level on tuning and peak shifting
  • Behaviour test for level-related peak shifting
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Determining factors for BM vibration - stiffness gradients

A

Stiffness determined by BM width and thickness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Determining factors for BM vibration - mass gradients

A

Mass determined by the size of organ of Corti

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Determining factors for BM vibration - effect

A

Phase/time delay of different value

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Determining factors for BM vibration - results

A

BM vibration as traveling wave from base to apex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Bekesy’s measurement of BM displacement
- how did he observe the traveling wave?
- what was freq. limited to?

A

Bekesy Worked in telephone company to design telephone/ earphone

Led to his 1928 discovery of mechanical vibration of inner ear

Dissection of cochlea

Observation of traveling wave using stroboscopic device on motion of silver particles.

Limited to fre. <1600 Hz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the direction of the travelling wave?

A

base to apex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the peak location of the travelling wave?

A

The natural frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The travelling wave is an ____ envelope

A

asymmetric

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

The travelling wave is ____ for ____ frequencies.

A

broader, low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

The travelling wave speeds up toward the ____ then fades away.

A

peak

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What two things is the travelling wave not equal too?

A

signal frequency and sound speed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why does vibration travel?

A
  • Mass gradient***
  • Larger mass = larger time delay (slower response)
  • Cause phase delay varied along cochlear duct
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is not the reason of vibration travel?

A
  • Not due to sound getting into cochlea via stapes
  • Evidence? If we apply the sound source to the apex the traveling wave still occurs and travels from the base to the apex
    o Sound travels faster in water/fluid so it doesn’t take long for the sound to travel the whole cochlea
    o Traveling wave is faster at high freq. and slower at low freq. region
    o Faster the traveling wave the better the synchronization
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What component did Bekesy not include?

A

The active component

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Explain the importance of the active component

A
  1. Active component is dominant at low sound level. Passive one is dominated at high levels
  2. Overall amplitude of active component is smaller than the passive one at higher sound levels.
  3. Active m. require healthy cochlea

2 and 3 make the active component more difficult to record

Active component is OHC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is required for measuring the active component?

A
  1. living, healthy OHCs
  2. low sound level
  3. highly sensitive equipment
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

BM response in dead and living cochlea (pic 1)

A

Black lines: responses of dead cochlea
Red lines: responses of living (healthy cochlea)

At low sound level, cochlea with healthy OHCs shows sharper tuning, larger amplitude in its BM vibration than the dead/passive cochlea

At high sound levels, the BM vibration is similar between healthy/active cochlea and dead/passive one

Passive = black line (small but goes to larger areas)
Active = red line is localized

Don’t know the active component when the sound level is high

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the 3 methods to observe BM vibration?

A
  1. capacity probe
  2. mossbauer technique
  3. Laser doppler interferometry
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Capacity probe

A
  • Capacitor: two conductive plates separated by a non-conductive layer
  • The probe serves as one plate, BM the other one
  • Dry air in between is the insolation.
  • BM vibration change the distance between the two plate and therefore the capacitance change.
  • Require water to be drained, bad for cochlea
  • Sensitivity is poor
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Mössbauer technique

A
  • Doppler effect: signal frequency changes by the relative speed between the generator and receiver (when you hear an airplane it sounds high pitch then the pitch becomes lower, however the pitch isn’t changing)
  • radioactive material applied to BM to produce signal of known frequency
  • Receive test vibration of BM by measuring the frequency change
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Laser Doppler Interferometry

A
  • Doppler shifting from light reflection (from applied glass balls, or from cellular fat)
  • Most modern method
  • A laser beam is applied
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Where is surgery easiest?

A
  • Easier at basal and apical ends
  • measurement is limited to basal and apical ends
  • apical end and round window are the 2 things that produce the minimum emission damage to ensure the health of the cochlea
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Pattern versus point

A

Point Test
- Point test requires smaller surgical opening, therefore smaller damage
- More practical
- In point test, signal frequency is changed, and the probe location is fixed
- How do we get overall pattern from point test? Accumulate results from hundreds of animals
- Put all the points together and get the pattern

Pattern Test
- Overall pattern of vibration can be elicited by test at multiple points, from multiple subjects.
- In pattern test, probe location is changed, not signal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Displacement versus Speed (velocity)

A

Vibration at high frequency cannot have large displacement; therefore, amplitude is small.

Velocity test is fair to compare across different frequency regions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

BM frequency selectivity in point test: two types of curves

A

Iso-intensity-amplitude curve

Frequency-threshold curve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Iso-intensity-amplitude curve

A

how amplitude change with frequency at the same sound level

CF is the peak in the tuning curve

Best frequency matches the CF

Largest vibration is produced by a lower frequency (lower than CF) – because of travelling wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Frequency-threshold curve

A

Similar to tuning curve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Key point to remember in point tests

A

The test is done at a fixed location, so the results are vibration that can be seen at this point. Stimulation varies in intensity and frequency.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Frequency selectivity of receptor potential

A
  • Basilar freq. (BF) changes seen in receptor potential
  • BF shifts to low freq. at higher intensity
  • Increasing sound level –> shift to low freq. side/point
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Gain changes with ____ level

A

sound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Explain gain and vibration in correlation to sound level

A

If sound level is 3dB SPL, gain can go up very high (lower the sound level, larger the gain)

When sound is high, gain is reduced

Gain reduces with sound level, although vibration amplitude (here is measured as speed) increases with intensity. “Best frequency” shifted downward to low frequencies in both graphs.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Tuning becomes wider with an increase in ____

A

Sound pressure level (SPL)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

BF shifts to low frequency with increase in ____ at a fixed point

A

Sound pressure level (SPL)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

A low frequency signal produces a vibration that is spread to…

A

higher frequency region at high sound level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What does BM vibration look like over the whole cochlea but by a fixed frequency?

A
  • The overall vibration across cochlea can’t be directly measured
  • Cochlea integrity will be lost if we open the shell too much
  • The overall view of the vibration must be obtained from multiple points
  • Vibration by a fixed frequency across levels
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Explain a point test

A

The result of point test, showing the vibration seen at a fixed point (with CF 10 kHz) in response to sound of different level and frequency.

Freq. decreases with sound level

In point test, BF decreases with increased sound level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Explain a pattern test

A

The vibration pattern by testing at multiple sites in response to a tone of fixed frequency (14.5 kHz) but different levels.

Freq. increases with sound level

In overall pattern: vibration peak shifts towards basal end (higher frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Are point and pattern conflicting?

A

Yes

40
Q

This is the test of ____ is not fair for evaluating vibration at high freq.

A

displacement

41
Q

Why is there a peak shift?

A

From acoustic trauma

42
Q

Explain acoustic trauma

A
  • Applying 4kHz tone at high intensity
  • TTS (temporal threshold shift) and PTS (permanent threshold shift) are maximal at 6 kHz
  • So as the hair cell loss
  • Half-octave Law
  • Hearing loss produced at 4k tone shifts to high freq. region
    Noise induced hearing loss is the half octave law (largest damage occurs half octave above the freq. of noise exposure)
43
Q

BM response in dead and living cochlea - Low sound levels

A

At low sound level, cochlea with healthy OHCs shows sharper tuning, larger amplitude in its BM vibration than the dead/passive cochlea

44
Q

BM response in dead and living cochlea - High sound levels

A

At high sound levels, the BM vibration is similar between healthy/active cochlea and dead/passive one

45
Q

Time interval allows BM vibration to be ____ and therefore the use of ____.

A

reduced, low-level probe

46
Q

What are the main points stimulation of HC and cochlear transduction

A
  • BM vibration to shearing or bending
  • Bending of stereocillia to open ion channels
  • Current (carried by potassium) to potential
  • AC vs. DC response
  • Ion channels involved
  • Behaviour or receptor potential is nonlinearity
47
Q

Do the OHC touch the tectorial membrane?

A

The tallest sterocillia in OHC are embedded in the tectorial membrane

48
Q

Different ways for hair bundle bending between IHCs and OHCs

A

OHCs are embedded in the tectorial membrane

Hair bundles on IHCs are not embedded in TM

Bending is driven by Hensen’s strip and hydraulic force

49
Q

How many rows are there of OHC?

A

3 rows

50
Q

Explain the difference between IHC and OHC links

A

The links across the stereocilia of IHC are not as strong as OHC (people think the stereocilia of IHC are freely vibrating alone)

51
Q

Different OHC links

A

Three types of links:
1) Row-to-row
2) Side-to-side
3) Tip-to-side (tiplink)

1) And 2) are thicker, they hold the stereocilia together, control the stereocillia in groups

3) Control MET channels

52
Q

Stereocilia on IHC are driven by ____, there are no strong row/side links

A

hydraulic force

53
Q

Why is it good that the IHCs are free of strong links?

A

Being free of strong links across the stereocilia make them easier to bend in response to hydraulic turbulence

54
Q

Explain the battery theory

A

In order for the HC to function as a receptor (to produce receptor potential) there are 2 batteries that are connected.

The more powerful one is on the surface of the scala vascularis, the smaller one is on the individual hair cell (which makes the intracellular potential negative -60mv)

The battery from the SV makes the SM +80mv

Together, the total is 140 mv (favours the movement of potassium from SM into hair cells)

55
Q

Explain the standing current

A

Current when there is no stimulation

Always baseline opening of MET channel and small amount of potassium diffusion across supporting cells & BM

Standing current: goes from SV, SM, organ of corti, perilymph, and back to SV (or SV, across BM, and back to SV)

Nothing to do with sound, happens without sound stimulation

Largely occurs across OC (not a waste of energy)

56
Q

Transduction channels

A

Location: inside the stereocillia

Ion selectivity: not selectivity

Gating function: controlled by tip links (voltage, light, temperature, pressure, force), mechanically gated which is controlled by the tiplinks

57
Q

What does the Holt and Corey PNAS model propose?

A

That a channel is located around the tip, but also the side of the stereocillia

58
Q

The entrance of MET channels are likely located at the ____ of tip link on the shorter stereocilia.

A

root

59
Q

What is CDH23?

A

Gene that has been recognized as a gene in animals for aging related hearing loss (this gene has not been found in humans), only partially related

60
Q

Summary of ion channels involved in HC functions

A
  1. Bending to excitation causes opening of MET channel, this opening is controlled by calcium (calcium can also pass the MET channel) – MET cannot remain open for a long time
  2. Intracellular potassium level increases (potassium channel is voltage gated) – there is no link between calcium and potassium channel on lateral wall
  3. Calcium triggers the release of NT
61
Q

Sequential events in HC response to sound

A

Deflection—transduction channel opening, transduction current increase

K inward—depolarization

ICa increase causes:
- IK increase—repolarization
- Neurotransmitter release

AP of auditory N

62
Q

Stereocilia deflection & receptor current

A

No deflection: standing current balanced by outward current-resting potential

Deflection towards kinocilium (laterally in cochlea) increases inward current –> depolarization and cause 8th firing

Deflection towards modiolus (medially), decreases inward current (hyperpolarization)

63
Q

Hair Bending Receptor Potential

A

Depolarization and hyperpolarization periods are very short

Depolarization = higher chance of AP

64
Q

The impact of frequency on receptor potential - AC component

A

The AC component amplitude is decreased with increasing frequency:
- Due to capacitance and resistance of the membrane: low-pass feature
- Due to the low-pass feature of recording electrode
- How this impact OHC motility?

65
Q

The impact of frequency on receptor potential - DC component

A

The DC component amplitude is increased with frequency
- During the stimulation, K is accumulated inside HCs,
- This is more significant when signal frequency is high, due to lack of time to remove K.

66
Q

Nonlinearity in CM response-level function

A

Noting that the dynamic range for CM is larger than that of typical range for auditory nerve, suggesting that the cochlear compression is not fully established at CM level but at the active feedback from OHCs to IHCs.

By increasing sound level from low to high, CM amplitude increases then saturates when sound level is very high

OHC functions as an amplifier

67
Q

Key points of cochlear nonlinearity
- how is it shown?
- where does it originate?
- what does it depend on?
- what is it vulnerable to?
- what does it require?

A

Shown in different ways: response-level function; distortion products in OAE

Originates from inside cochlea

Depends on active mechanism

Vulnerable to damaging factors

Requires intact OHCs

68
Q

Where does nonlinearity occur?

A

Nonlinearity occurs in a restricted area around CF, where rapid increase was seen at low-moderate intensity; saturated at high level.
Linear growth at freq. away from CF

69
Q

Cochlear amplification (what is it from and what does it do)?

A

From OHC motility

Provides sharp tuning (?)
- Don’t see motility showing any sharp tuning or freq. selectivity, so we don’t know why HC at different location show different freq.

Provides high sensitivity

70
Q

Explain what happens during BM vibration at low sound level in active and passive cochlea

A

Active component by OHC increase the sensitivity and tuning

Vibration from low level sound in passive cochlea is so small it cannot be detected

71
Q

When HCs are excited they become ____.

A

shorter

72
Q

Amplitude difference between BM and RL is larger at ____ sound level

A

low

73
Q

Amplitude difference between BM and RL

A

Theoretically, the difference in amplitude between BM and RL can be considered as the gain by OHCs, which is larger at low sound level.

74
Q

Where is sharp tuning seen?

A

Sharp tuning seen in receptor potential, BM vibration and auditory nerve

No need for second filter

Or OHC motors are second filters

75
Q

Sharp tuning and nonlinearity depend on ____

A

OHC

76
Q

OHCs as motor (comes from what 3 lines of evidence)?

A

Comes from 3 lines of evidence
1. Dallas: OHC lesions elevate threshold
2. Brownell: OHCs motion in response to voltage changes
3. Many researchers: OHC motility contributes to cochlear amplifier

Receptor potential activates motors

Motor must be something that can be electrically driven

77
Q

Types of OHC motility

A

Fast motility of OHC bodies (mostly understood & responsible for active mechanism)

Slow motility of OHC bodies (refers to shift change in response to ion change - not main concern & does not contribute to active mechanism)
- K+, Ca++, and ATP

Motility of hair bundles (not seen in mammal cochlea)

78
Q

General feature of fast motility of OHC body
- what does it follow?
- why is it different from muscles?
- how is it driven?
- length change?

A

Fast: follows hearing frequency range

Different from muscles: independent of ATP and Ca++, does not require muscular proteins (actin and myosin)

Fast motility is driven by voltage difference across cell membrane

Asymmetric length change up to 5%, without volume change

79
Q

What are 2 methods for recording fast motility?

A

whole patch and microchamber

80
Q

Fast motor

A

A protein in plasma membrane

Prestin is rich in OHC, not in IHC

Gene: SLC26A5

81
Q

Prestin appears at the same time as ____ after birth

A

OHC motility

82
Q

Prestin is related to ____

A

fast motility

83
Q

Explain fast OHC body motility
- what is it proportional to?
- how fast can it flow?
- how much does the length change?

A

Proportional to MP (membrane potential) changes

Fast: flows up to 20 kHz

Length change up to 5% - 1-5 um, comparable to BM vibration by sound

84
Q

When hyperpolarized, protein moves ____, when depolarized, protein moves ____.

A

in, out

85
Q

When HC moves medially it ____, when HC moves laterally it ____.

A

elongates, shortens

86
Q

How does OHC motility enhance stimulation to IHCs

A

Not clear

Maybe by hydraulic turbulence

Maybe by changing the interaction from tectorial membrane (shortening of IHC length may pull the tectorial membrane closer to reticular lamina)

No methodology can ensure a reliable observation in this small area

87
Q

How OHC length change impacts coupling to IHCs?

A

OHC shortening reduces the distance between IHC and TM

88
Q

What is the structure of prestin at high frequency?

A

AA for high frequency

89
Q

How the gain is changed over sound level

A
  • Larger gain at low sound level
  • Smaller gain at high sound level
  • We don’t know if the motility of OHCs saturate with increasing sound level
  • The response of IHCs and ANFs becomes saturated at high sound level. Do they related to the automatic gain control?
90
Q

How is the cochlear amplification/motility tuned?

A
  • Electrical resonance of HC (not in mammal)
  • Mechanical resonance of BM
  • Tonotopic differences in the stiffness of hair bundles.
91
Q

HCs in amphibians, reptiles and birds are tuned (electrically), not seen in OHCs of ____.

A

mammals

92
Q

Motility of hair bundle
- what animal shows best frequency
- what does oscillation follow?
- what drives hair bundle to move?

A
  • The electrical resonance in turtle HCs shows best frequency (turned)
  • Oscillation following membrane potential
  • The electrical resonance may drive hair bundle to move
93
Q

Mechanism for amplification tuning in mammals (are OHC sharply tuned)?

A
  • OHC motility is not sharply tuned
  • The sharp tuning of BM by OHCs is not fully understood.
    o “initiated” from BM passive tuning
    o From hair bundle motility?
  • Hair bundle motility is seen in amphibians, not in mammals
  • Is it possible?
94
Q

New evidence for hair bundle motility in mammalian cochlea

A
  • In mammals, stiffness change with deflection
  • More recently, length change
95
Q

Is there hair bundle motility in mammals?

A
  • It is likely, but no evidence yet
  • If not, cannot explain frequency selectivity of OHC amplification
  • But the evidence is not solid yet.

Audition II (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions