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Cogs 101A > Week 7 > Flashcards

Week 7 Flashcards

1
Q

Middle ear

A

Two cubic centimeter cavity separating inner from outer ear

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2
Q

Middle ear contains three ossicles:

A

Malleus
Incus
Stapes

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3
Q

Malleus

A

Moves due to the vibration of the tympanic membrane (eardrum)

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4
Q

Incus

A

Transmits vibrations of malleus

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5
Q

Stapes

A

Transmit vibrations of incus to the inner ear via the oval window of the cochlea

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6
Q

The outer and middle ear are filled with _____.

A

Air

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7
Q

The inner ear is filled with ____ that is much ____ than air.

A

Fluid; Denser.

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8
Q

Pressure changes in the air transmit ____ Inyo the denser medium

A

Poorly
- Less than 1% of the vibration can transmit directly.

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9
Q

The ossicles act to ____ the vibration for better transmission to the fluid.

A

Amplify
- Can do this up to a factor 50.

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10
Q

Pinna

A

(Outer ear)
Helps with sound location and amplification and is responsible for steering signal into auditory canal.

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11
Q

Auditory Canal

A

Tube-like structure just long enough to protect the tympanic membrane (eardrum) at the closed end.
- sound waves reflect off the end of the canal and create resonance.

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12
Q

Acoustic reflex of the ossicles

A

Can reduce transmission of loud sounds by about 20 dB.

Middle ear muscles can dampen the ossicles’ vibration to protect the inner ear from potentially damaging the stimuli.

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13
Q

The main structuere of the inner ear is the ___.

A

cochlea

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14
Q

Cochlea

A

Where sound waves are traduced into neural signals.
- fluid-filled, snail-shaped.
- sound waves are transduced into neural signals within the cochlea.
- vibrates with motion of the stapes and eardrum.
-signals will be transmitted out of the cochlea via the auditory nerve.

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15
Q

The ___- pushes against the _____, transmitting atmospheric vibrations directly to the inner ear.

A

Stapes; oval window.

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16
Q

Structure of the cochlea

A
  • Hard, bony
  • Divided into the scala vestibule (above) and scala tympani (below) by the cochlear partition.
  • Cochlear partition extends from the base (stapes end) to the apex (top end). Base > Apex
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17
Q

What is contained within the cochlear partition (in the scala media)?

A

Organ of Corti

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18
Q

Where does transduction occur?

A

In the organ of Corti
- sits on the basilar membrane
- basilar membrane vibrates in response to sound and supports the organ of Corti
- inner ((~3500) and outer hair cells (~12000) are the receptors used for hearing.

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19
Q

Transduction takes place by:

A

Stereocilia

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20
Q

Stereocilia

A

Hair cells

Heir cells bending in response to pressure changes from vibration of the Organ of Corti against the tectorial membrane or fluid surrounding it.

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21
Q

Movement of inner hair cell Stereocilia in one direction

A

Opens ion channels via tip links.
Movement in other direction closes the channels
Outer hair cells amplify this.

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22
Q

Two ways nerve fibers can signal frequency:

A
  1. Which/Where nerve fibers are responding.
    - specific groups of hair cells on bail ar membrane activate a specific set of nerve fibers.
    - place theory
  2. How/When fibers are firing
    - rate or pattern of filing of nerve impulses.
    - temporal coding
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23
Q

Place theory

A

Georg Von Bekesy’s place theory of hearing says that the frequency of sound is indicated by the location/place (of hair cells) along the cochlea that has the highest firing rate.

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24
Q

Two ways Bekesy determined place theory:

A
  1. Through the direct observation of the vibrational properties of the basilar membrane in cadavers.
  2. By building a model of the cochlea using the physical properties of the basilar membrane.
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25
Q

Basilar Membrane

A
  • The base of the membrane is 3 or 4 times narrower than at the apex and 100 times stiffer than at the apex.
  • Both the model and observation (Bekesy) showed that the vibrating motion of the membrane is a traveling wave (like snapping a rope)
26
Q

Envelope of the traveling wave

A
  • Most of the basilar membrane vibrates in response to a traveling wave, but the displacement is largest in one place.
  • Hair cells at this maximum point are stimulated the strongest, leading to the nerve fibers firing the most at this location.
  • The envelope shows the entire displacement caused by a traveling wave and its peak.
27
Q

Envelopes at different frequencies

A
  • Show that different maximum vibration points, which indicate the place where most hair cell activity is predicted.
    -**Low* frequencies activate hair cells toward the apex, while high frequencies activate hair cells near the base.
28
Q

If I play a pure tone at 100 Hz, it will be transduced by ____ hair cells nearest the _____ of the cochlea.

A

Inner; Apex

29
Q

Electrode recordings have supported Place Theory

A
  • Electrodes were placed outside the cochlea of guinea pig while different pure frequency tones were presented.
  • Cochlea shows an orderly map of frequencies along its length.
    -Apex responds best to low frequencies.
    -Base responds best to high frequencies.
    -This is called a tonotopic map*
30
Q

Neural frequency curves provide physiological support for Place Theory.

A
  • Pure tones are used to determine the threshold for specific frequencies measured at single neurons.
  • Record action potentials from one auditory nerve fiber along the cochlea and play tones at different frequencies.
  • Plotting threshold for frequencies results in tuning curves.
31
Q

Frequency to which the neuron is most sensitive (lowest threshold) is the:

A

Characteristic frequency

32
Q

Auditory masking experiments

A
  1. Thresholds for a number of frequencies are determined.
  2. Then an intense masking frequency is presented at the same time that the thresholds for the original frequencies are re-determined.
  3. The masking effect (raised threshold) is seen at the masking tone’s frequency and spreads to higher frequencies more than lower ones.
33
Q

Understanding the masking effect:

A
  • This effect aligns with the place theory’s prediction about how he basilar membrane responds to sound..
34
Q

Evaluating the Basilar Membrane

A
  • Physical properties of the basilar membrane are key to understanding place theory.
  • Base of the membrane is narrower and stiffer, leading to a traveling wave for sound transduction.
35
Q

Outer hair cells, cochlear amplifier, responds to sound by …

A

Slight tilting and a change in length.
These cells enhance the sensitivity and frequency selectivity of the cochlea.

36
Q

Better Bekesy

A
  • Original place theory predicted less sensitivity to frequency difference.
  • Live membrane research shows outer hair cells respond by tilting and changing length, acting as a cochlear amplifier.
37
Q

Cochlear Amplifier

A

Outer hair cells enhance the ear’s sensitivity and selectivity for sound frequencies

38
Q

Encoding sound intensity

A

Sound intensity is encoded by movement of the basilar membrane and the activity of the cochlear amplifier.

39
Q

Encoding Sound Intensity:
Inner hair cells are activated _____ with_______ sound intensity, and neighboring cells also respond ___.

A

More; increased; more

40
Q

Encoding Sound Intensity
Impact of outer Hair Cells:

A

Selective destruction of outer hair cells shows a decrease in the firing rate of inner hair cells, indicating their role in amplifying characteristic frequency.

41
Q

Complex Tone Analysis

A
  • The basilar membrane acts like an acoustic prism, separating complex tones into their harmonic components.
  • Each peak in membrane vibration corresponds to a harmonic frequency.
42
Q

Fourier Analysis in Hearing

A
  • Fourier analysis can break down complex waves into individual components, mirroring how the ear processes complex sounds.
43
Q

Phase Locking

A
  • Nerve fibers fire in bursts at or near the peak of the traveling wave, locking in phase with the wave.
  • The refractory period post-firing establishes a limit for individual signaling capacity.
44
Q

Auditory Nerve Fiber Firing

A

Illustration of inner hair cells with auditory nerve fiber firing patterns synchronized with the sound stimulus.

45
Q

Fibers may fire at different ____, allowing a group fo neurons to encode a broader range of frequencies.

A

Peaks

46
Q

Combining neuron activity can create frequencies beyond a _____ neuron’s capacity

A

Single

47
Q

Place coding provides information for

A

the broad frequency range of hearing.

48
Q

Temporal coding with phase locking us effective for frequencies up to ___ kHz.

A

4-5

49
Q

Coding Frequency and Pitch

A

Both coding strategies work together, with temporal coding playing a significant role in pitch perception.

50
Q

Types of Hearing Loss

A

Conductive hearing loss
Sensineural hearing loss

51
Q

Conductive hearing loss

A

Involves blockages or garage to the outer or middle ear structures

52
Q

Sensineural hearing loss

A

Results from damage to the hair cells or auditory nerve

53
Q

Chemical Ablation

A

Selective destroying of outer hair cells

54
Q

If I play a complex sound into teh ear, teh traveling wave vibrating the basilar membrane will have:

A. A single peak at the highest amplitude frequency
B. A peak for every frequency
C. No peak
D. A peak at the fundamental frequency

A

B

55
Q

Amplitude modulated noise

A

The primary change in intensity results in the perception of pitch

56
Q

Presbycusis (old hearing)

A
  • Age related hear loss (ARHL)
  • Greatest loss is at higher frequencies (>12 kHz)
  • Affects men more
  • May change with behavior.
57
Q

What can presbycusis be cause by?

A

Accumulated exposure to damaging noises o drugs over a lifetime.

58
Q

Mosquito Mk4

A

Old person use mosquito noise to keep away teenagers lol.

59
Q

Mosquito ringtone

A

Teachers (ppl older than 30) can’t hear text/call ringtone.

60
Q

Noise-Induced Hearing Loss

A
  • Loud Noise can severely damage the Organ of Corti (loss of inner and outer cells)
  • Damage associated with certain types of work (factory, heavy machinery)
  • Leisure noise can also cause hearing loss (earbuds!!!)
61
Q

Pitch neurons

A

Cell just outside A1 and responds to complex tones with the same fundamental frequency

Bendor & Wang

62
Q

What happened when Norman-Haignere used fMRI to measure responses to complex tones perceived as a pitch (110Hz) and frequency-matched noise?

A
  • The noise stimuli contained all the frequencies, but wasn’t perceived as having a specific pitch.
  • Areas in anterior auditory cortex were more responsive to pitch.

Cogs 101A (10 decks)

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