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Intro to Brain and Behavior > Chapter 11: Auditory > Flashcards

Chapter 11: Auditory Flashcards

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1
Q

What is sound?

A

Audible variations in air pressure

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2
Q

What is compressed ai?

A

Particles that are packed close together

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3
Q

What is rarefied air?

A

Particles that are spread out

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4
Q

What does compressed air create in air pressure?

A

Condensation

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5
Q

What does rarefied air create in air pressure?

A

Rarefaction

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6
Q

What is cycle?

A

Distance between successive compressed patches

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7
Q

What is pitch (sound frequency)?

A

Number of cycles per second
Hertz (Hz)

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8
Q

What is intensity (amplitude)?

A

Size of the pressure variation away from the constant atmospheric pressure

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9
Q

What is phase?

A

Location of the sine wave relative to some time point

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10
Q

What is the range of frequencies that are perceived as sound for humans?

A

20 Hz to 20KHz

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11
Q

What is the outer ear?

A

Pinna conducts sounds into the auditory canal towards the tympanic membrane

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12
Q

What are the parts of the middle ear?

A

Tympanic membrane, ossicles (malleus, incus, stapes)

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13
Q

What is the inner ear?

A

Cochlea

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14
Q

What is the simplified version of auditory transduction?

A
  1. Sound waves move tympanic membrane
  2. Tympanice membrane moves ossicles
  3. Ossicles move membrane at oval window
  4. Motion at oval window moves fluid in cochlea
  5. Movement of fluid in cochlea causes response in sensory neurons
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15
Q

What does the middle ear do?

A

Amplifies sound

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16
Q

What are the mechanisms used to overcome energy mismatch between air and water in the ear?

A

Lever-arm ratio and area ratio

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17
Q

What is the lever-arm ratio?

A

The ossicles act as levers. The malleus arm is longer than the incus arm. Thus, the level action multiples the force around 1.3 times

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18
Q

What is the area ratio?

A

This is the main mechanism used.
There is amplification due to the larger area of the tympanic membrane compared to the footplate of the stapes in the oval window.

19
Q

What is the attenuation reflex?

A

An onset of a loud sound triggers stapedius and tensor tympani muscles to contract and sound conduction to inner ear is greatly reduced.
It is also activated when we speak so we don’t hear our voices as loudly as we otherwise would.

20
Q

Which nerves are in the process of the attenuation reflex?

A

Tensor tympani muscle (CN VII)
Stapedius Muscle (CN V)

21
Q

What is the job of the attenuation reflux?

A

It protects inner ear from loud sounds that would otherwise damage it.

22
Q

What are the 3 scalae of the cochlea?

A

Scala vestibuli
Scala Media
Scala Tympani

23
Q

What is perilymph?

A

A fluid in scala vestibuli and scala tympani
Its composition is like extracellular fluid - low K high Na

24
Q

What is endolymph?

A

A fluid in scala media
Its composition is like intracellular fluid- high K low Na

25
Q

What is stria vascularis?

A

Pumps K+ into scala media

26
Q

Where is sound transduction accomplished?

A

In the Organ of Corti that sits on Basilar membrane

27
Q

What does the cochlea do with complex sounds?

A

The cochlea is the frequency analyzer.
It breaks incoming complex sounds down into their component frequencies.

28
Q

What does the basilar membrane do?

A

It moves up and down with movement of perilymph

29
Q

What are the properties of the base of the basilar membrane?

A

It is narrow and stiff.
It processes High frequency.

30
Q

What are the properties of the apex of the basilar membrane?

A

It is wide and floppy.
Processes low frequency

31
Q

What does the organ of corti do?

A

Its motion causes changes in membrane potential

32
Q

What are the spiral ganglion cells?

A

They receive input from the hair cells and project to the brain in the auditory component of the vestibulocochlear nerve.
This is where the cell bodies of neurons that form synapses on hair cells.

33
Q

What is a hair cell?

A

It is in the organ of corti.
It has stereocilia on top of hair cell.
It forms synapses with the 8th cranial nerve

34
Q

How many hair cells are there?

A

There is 3 rows of outer hair cells and 1 row of inner hair cells on the organ of corti.

35
Q

What causes changes in membrane potential in hair cells?

A

Displacement of the basilar membrane causes deflection of stereocilia on hair cells which leads to changes in membrane potential in hair cells.

36
Q

What causes the depolarization of hair cells?

A

Movement toward the tallest stereocilia opens mechanically gated channels and depolarizes cell.
Hair cells can’t create AP but it is the 8th nerve that can fire an AP.

37
Q

What causes the hyperpolarization of hair cells?

A

Movement away from the tallest stereocilia hyperpolarizes the cell.

38
Q

How are mechanically-gated channels on hair cell connected?

A

They are connected by tip links that are elastic filaments.

39
Q

How is the hair cell at rest?

A

At rest some of the mechanically gated channels are open allowing K+ while other channels are closed.
It’s membrane potential is -70mV due to perilymph.
In the endolymph very high amount of K+

40
Q

What is the process of depolarization of a hair cell?

A

Movement towards tallest stereocilia causes mechanically-gated channels to open allowing K+ in.
Leads to depolarization that opens voltage-gated Ca++ channels
Ca++ influx triggers release of neurotransmitter (vesicle formation).
Leads to 8th nerve afferents to depolarize.

41
Q

How do the hair cell receptor potentials look like?

A

They resemble the sound pressure wave.
They faithfully follow stimulating waveform for low frequencies.

42
Q

How does the hair cell receptor potential look like for high frequencies?

A

Since the basilar membrane is moving too fast due to high frequency the hair cells stop following the waveform of sound and instead just stay depolarized.

43
Q

What are outer hair cells?

A

They are 80% of all hair cells.
5% are of afferent innervation.
They receive most of the efferents from the CNS and can modulate the sensitivity of the inner hair cells.

44
Q

What are inner hair cells?

A

They are 20% of all hair cells.
95% of afferent innervation.

Intro to Brain and Behavior (12 decks)

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