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AUDE 5160 - Anatomy > Inner Ear Review 3 > Flashcards

Inner Ear Review 3 Flashcards

1
Q

What is the partition consisted of?

A

BM, tectorial membrane, organ of corti

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2
Q

Tonotopic arrangement

A

Different regions of the basilar membrane vibrate at different sinusoidal frequencies due to variations in thickness and width along the length of the membrane

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3
Q

he place of basilar membrane motion is thought to be directly related to perceived

A

pitch

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4
Q

Process of the hair cells transmitting NT to the cochlear nerve

A
  1. Tectorial membrane moves and stimulates the stereocilia
  2. Links on the stereocilia open to allow potassium to flow into the cell (depolarizes)
  3. Calcium flows into the cell through ion channels
  4. Triggers glutamate+ to go to the synaptic cleft
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5
Q

Process of the refractory period after a hair cell fires

A
  1. Potassium is reabsorbed into the cortilymph
  2. Stria vascularis takes up potassium again to recycle it into the endolymph
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6
Q

If the fluid moves the hair cells from tall to short, this will:

A

Inhibit the influx of potassium (hyperpolarize)

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7
Q

What factors help us sensory code sounds?

A

intensity frequency pitch

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8
Q

Why do we need the hair cells to “sharpen” the incoming signals?

A

to differentiat between pitches/frequencies (aka active mechanism)

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9
Q

Absolute refractory period

A

time during which another action potential is impossible; limits maximal firing rate

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10
Q

relative refractory period

A

the period of time following an action potential, when it is possible, but difficult, for the neuron to fire a second action potential, due to the fact that the membrane is further from threshold potential (hyperpolarized)

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11
Q

4 characteristics of an action potential

A
  1. Self propogating
  2. Forward transmission
  3. Unidirectional
  4. No degradation over time
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12
Q

the place of the basilar membrane motion is related to ____

A

frequency and pitch

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13
Q

the BM is ____ and ____ at the base

A

narrow and stiff (high frequencies)

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14
Q

the BM is ____ and ____ at the apex

A

wide and floppy (low frequencies)

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15
Q

what type of frequencies are more suceptible to damage?

A

high frequencies (at the base, get all input all the time)

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16
Q

primary function of inner hair cells

A

send information about sound to the brain

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17
Q

axosomatic

A

nerves that connect an axon to a soma

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18
Q

shape of outer hair cells

A

test tube shaped, don’t have a bulge

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19
Q

shape of inner hair cells

A

flask shaped, have a bulge in the middle

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20
Q

what are the main afferents?

A

IHC

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21
Q

What are the main efferents?

A

OHCs

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22
Q

What is the kinocilium?

A

guiding body for the hair cell stereocilia to align during embryologic development

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23
Q

What happens to kinocilium after birth?

A

becomes rudimentary

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24
Q

stereocilia are arranged by what factor

A

height

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25
Q

stereocilia connect to each other through

A

tips and side links

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26
Q

What is one major difference in OHC?

A

lined with prestin (matrix like format and form of muscle tissue for movement)

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27
Q

how many OHC do humans have?

A

12,000

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28
Q

How many IHC do we have (in total)?

A

4,000

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29
Q

Are frequency ranges among different species the same?

A

no, vary due to the size of hearing systems

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30
Q

most common type of cochlear damage

A

OHC damage

31
Q

what type of loss is associated with OHC damage

A

sensory HL, 40 dB loss, mild to moderately severe

32
Q

if both IHC and OHC are gone, what degree of hearing loss will we have?

A

severe to profound

33
Q

most common neurotransmitter in ear

A

glutamate

34
Q

What kind of sound stimuli do the OHC amplify?

A

low (0-40dB)

35
Q

What is our auditory accessory structure?

A

tectorial membrane

36
Q

Is the receptor potential directly transmitting information to the receptor neuron?

A

No, it doesn’t directly transmit information… goes through the synaptic cleft

37
Q

What excites the neuron

A

neurotransmitter

38
Q

If fluid moves the hair cells from short to tall, this will:

A

Excite the system, cause an influx of potassium (depolarize)

39
Q

What do we know about the action potentials of a hair cell at rest?

A

there are still firings happening

40
Q

What physical property of sound determines the displacement of the basilar membrane?

A

frequency

41
Q

How is neural firing different than cochlear nerve firing?

A

Sodium influx in brain instead of potassium firing in cochlea, potassium outflux in brain

42
Q

3 factors that influence encoding

A

intensity
frequency
firing code

43
Q

three factors when encoding intensity

A

rate
how many
fibers

44
Q

2 factors when encoding frequency

A

tonotopic organization
phase locking

45
Q

4 factors related to the firing pattern codes of OHC

A

Onset
duration
offset
envelope

46
Q

what makes a tuning curve “sharp” ?

A

amplification of the OHC (active mechanic amplifiers)

47
Q

if we have damage to the OHC, what will we see on a tuning curve?

A

“broad” tuning, not sharp

48
Q

what do our efferent fibers do for the inner ear system?

A

modulate / modify the OHC activity

49
Q

in what ways do the efferent fibers modulate the OHC activity?

A
  • reduce masking
  • selective attention
  • protect from intense sound
  • balance input from both ears
50
Q

how do OHC improve our sensitivity?

A

they make response thresholds lower (compress them –> nonlinear system)

51
Q

what are the cochlear receptors

A

IHC

52
Q

what do the IHC do?

A

generate receptor potentials (afferent)

53
Q

what crosses the synaptic cleft to stimulate CN 8 nerve fibers?

A

neurotransmitter (most common in aud system is glutamate+)

54
Q

at what point is an action potential generated?

A

when there is sufficient neurotransmitter

55
Q

how is neural firing different than cochlear firing?

A

NaK pump instead of just K (potassium)

56
Q

what concept explains why low frequencies can mask high frequencies but not vice versa?

A

upward spread of masking

57
Q

can a 200 Hz tone maska 1,000 Hz tone?

A

yes, upward spread of masking

58
Q

what do we know about the lowest point of the graph while looking at a tuning curve?

A

it is the characteristic frequenchy

59
Q

what is a PSTH

A

post-stimulus time histogram

60
Q

how do we graph a post-stimulus time histogram?

A

number of firing neurons on the y axis and time on x axis in milsec

61
Q

what does a “primary” or “primary-like” PSTH look like?

A

rest - peak - rest (initial spike and nothing else)

62
Q

describe a “pauser” response (PSTH)

A

spike – pause – buildup (primary with a pause)

63
Q

describe an “onset-chopper” response (PSTH)

A

spike – rest – spike – rest – spike – rest (increasing rest thresholds)

64
Q

is there only one type of cell in the cochlear nuclei?

A

no, there are pyramidal, octopus, stellate, spherical, and globular

65
Q

what are 2 excitatory neurotransmitters in the AVS

A

glutamate and aspartate (amino acids)

66
Q

what are 2 inhibitory neurotransmitters in the AVS

A

GABA and glycine

67
Q

what are 2 neurotransmitters in the “efferent” AVS pathway

A

acetylcholine and noradrenaline

68
Q

8CSlima

A
  • 8th nerve
  • cochlear nucleus
  • superior olivary complex
  • lateral lemniscus
  • inferior colliculus
  • medial geniculate body
  • auditory cortex (A1)
69
Q

What are the two largest categories of ototoxic drugs?

A

aminoglycocide and some members of the platinum chemotherapy drug family (carboplaton)

70
Q

Best describe the sodium-potassium pump

A

The main function of the pump is to maintain the resting potential by actively moving sodium out of the cell and potassium back in to restore the proper balance.

71
Q

Based on the 5 important functions of cell membrane proteins, clearly describe 3 of the important functions of such proteins that are on or in the cell membranes?

A

One important function of cell membrane proteins is that they have transmembrane ion channels that determine the electrical activity of the cell.

Another important function of cell membrane proteins is that they act as enzymes to catalyze biochemical reactions.

Cell membrane proteins also act as carrier proteins to help things cross the cell membrane. These carrier proteins can either be passive or active transport. When a carrier protein is an active transporter, it requires ATP.

72
Q

Briefly state two ways in which auditory nerve fibers are able to encode the frequency of an auditory stimulus.

A

Auditory nerve fibers encode frequency of auditory stimulus by the tonotopic arrangement of the cochlea. Different regions of the basilar membrane vibrate at different sinusoidal frequencies based on the thickness and width along it. The basilar membrane is designed so that it has a best region to vibrate for every frequency. For example, how high frequencies resonate best at the base and low frequencies closer to the apex.
Phase-locking-with action potential firing locking to a specific phase of incoming sound

73
Q

When an auditory stimulus reaches the cochlea what occurs to excite inner hair cells?

A

Potassium flows in through the open ion channels to depolarize the cell, causing a receptor potential

74
Q
A

AUDE 5160 - Anatomy (16 decks)

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