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Hearing A+P > Chapter 8 - Questions > Flashcards

Chapter 8 - Questions Flashcards

1
Q

What are the 5 main structures of the organ of corti?

A

inner hair cells, outer hair cells, stereocilia, tectorial membrane, basilar membrane

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2
Q

Are OHCs or IHCs stronger structurally?

A

IHCs

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3
Q

the nerve endings at the base of inner hair cells connect to:

A

the afferent fibers of the auditory nerve

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4
Q

the stereocilia of an IHC are arranged in ____ or more _______ rows that form a shallow ___ shape, and there are generally about ___ cilia per IHC

A

two; parallel; ‘U’; 40

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5
Q

What are the 3 support structures of OHCs?

A

Dieters cells, Hensen cells, Reticular lamina (membrane)

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6
Q

Where are Dieters cells found?

A

below the OHC

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7
Q

How many Dieters cells per OHC are there?

A

one

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8
Q

What is a hensen cells role?

A

lateral buttress

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9
Q

What does the Reticular Lamina do?

A

holds upper ends of the OHCs

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10
Q

the upper surface of an OHC contains about how many stereocilia?

A

150

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11
Q

stereocilia of OHCs are arranged in ____ or more rows in the shape of a ____, the bottom of which points toward ____ __________

A

3; ‘V’; stria vascularis

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12
Q

What is the physiology of a hair cell? (4 steps)

A
  1. Basilar membrane vibrates up and down 2. tectorial membrane hinges up and down 3. cilia bend (or ‘shear’) 4. nerve fires
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13
Q

the tips of stereocilia are linke by:

A

tip-links

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14
Q

displacement of the tip-links opens and closes:

A

ion channels

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15
Q

Inner hair cells do not exhibit ‘motility’ meaning:

A

IHC cilia do not differently connect to the tectorial membrane

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16
Q

the ICH cilia’s deflection is depend on:

A

fluid movement (like seaweed in the ocean)

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17
Q

IHCs are ________ cells.

A

sensory cell

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18
Q

OHCs are not all the same ______

A

length

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19
Q

What are two aspects of OHCs that give them strength or leverage?

A
  1. their V shape 2. the tallest are embedded in the tectorial membrane
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20
Q

What type of nerve fibers do IHCs have?

A

mainly auditory and afferent

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21
Q

What type of nerve fibers do OHCs have?

A

afferent and efferent auditory

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22
Q

What is the paradox of OHCs contacting the tectorial membrane and IHCs being dependent of fluid currents for activation?

A

IHCs have higher thresholds for response than OHCs, and IHCs have 90-95% of AN fibers connected to them, so what are the OHCs doing?

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23
Q

OHC stereocilia are embedded in the tectorial membrane, and the OHC motility affects position of the BM and TM so it affects vibration, based on this, what do the OHCs do?

A

modify vibrations, providing amplification and ‘tuning’

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24
Q

Define cochlear amplifier:

A

the idea that the OHC motility amplifies basilar membrane movement; it is a positive feedback loop; and the sensitivity of the cochlea traveling wave is amplified, making it easier for the IHCs to respond

25
Q

Endolymph (charge, comes from, lots of ?)

A

+80 mV ionic potential/charge, comes from stria vasularis, lots of potassium

26
Q

Perilymph (charge)

A

0 to +5 mV ionic potential/charge

27
Q

What is the charge of outer hair cells?

A

-70 mV

28
Q

What is the charge of inner hair cells?

A

-45 mV

29
Q

What is resting potential?

A

DC potential that exist without acoustic stimulation

30
Q

What is the endolymphatic potential (EP)?

A

endolymph +80 mV; the highest resting potential in the body

31
Q

What structure plays a role in maintaining the Endolymphatic Potential?

A

stria vascularis

32
Q

what is the high potential difference between the scala media and each outer hair cell?

A

~150 mV

33
Q

Shearing of stereocilia causes ___ ___________ to open, allowing _____________ (__+) from _____________ to flow into the hair cell. This initiates _____________________ of the cell.

A

ion channels; potassium (K+); endolymph; depolarization

34
Q

what is depolarization

A

the reduction of polarization

35
Q

What happens when the cell is depolarized? (2)

A

nerve cells fire and calcium channels open

36
Q

Once the calcium channels open, what happens?

A

the potassium channels open and potassium flows out of the cell, repolarizing it and making it ready to fire again

37
Q

how is the polarization process slightly different in hair cells than it is in the nervous system?

A

there is no sodium-potassium pump, no active sodium flow during potassium flow

38
Q

What are the 4 mechanical parts of cochlear biomechanics?

A
  1. vibration of stapes footplate 2. movement of oval window 3. vibration of cochlear fluids causes Basilar Membrane to move 4. cilia of hair cells bend/shear
39
Q

what is the cochlear physiology of neural transduction? (4)

A
  1. shearing of OHC stereocilia 2. opening and closing of ion channels (happens very fast - 40 microsecond) 3. depolarization of hair cell 4. generation of action potential (firing of auditory nerve)
40
Q

What are the two types of Afferent fibers?

A

Radial (Type I) and Outer spiral (Type II)

41
Q

What percentage of afferent fibers are type I and Type II?

A

Type I: 85-95%; Type II: 5-15%

42
Q

What kind of connection do Radial or type I fibers have?

A

many-to-one: 30,000 in each ear to 3500 IHCs

43
Q

what kind of connection do outer spiral or Type II fibers have?

A

one-to-many: ~10 OHCs per outer spiral fiber, 3,000 outer spirals to 12,000 OHC

44
Q

What do Type I fibers innervate?

A

the IHC exclusively, 1 or 2 ICHs/fibers only

45
Q

what do type II fibers innervate?

A

the outside row of OHC

46
Q

What are the 2 types of efferent fibers?

A

Lateral Olivary Complex (LOC) fibers and Medial Olivary Complex (MOC) fibers

47
Q

LOC fibers orginate from the ________ portion of the olivary complex. They are _____, _____________ fibers, and project mainly to the _____. They synapse on ________ nerves leaving the ____.

A

lateral; small, unmyelinated; ICH. afferent; IHC

48
Q

MOC fibers orginate from the ______ portion of the olivary complex. They are _____, _____________ fibers, and project mainly to the _____. They synapse directly to the ____ and one MOC could innervate as many as ____ hair cells.

A

medial; large, myelinated; OHC; OHC; 100

49
Q

True or False: MOC and LOC fibers can be either crossed or uncrossed

A

True

50
Q

The auditory nerve bundle is within the _________ and exits the cochlea through the _________ __________

A

modiolus; habenula perforata

51
Q

What is tonotopic organization?

A

different parts of the cochlea send information from different frequencies to different parts of the nerve bundle

52
Q

The middle of the nerve bundle innervates the ____ and transmits ___ frequency information

A

apex; low

53
Q

the outside fibers of the nerve bundle innervate the ____ and transmit ____ frequency information

A

base; high

54
Q

OHCs modify vibrations, providing amplification and “tuning.” What does tuning mean?

A

frequency selectivity (distinguishing pitch)

55
Q

ototoxic drug experiments are a way to understand what?

A

how ears work

56
Q

Kanamaycin was used experimentally to selectively damage what structure of the ear?

A

OHC

57
Q

Carboplatin (a chemo drug) was used experimentally to selectively damage what structure of the ear?

A

IHC

58
Q

the ototoxicity experiments doen with Carboplatin and Kanamycin showed what?

A

Kanamycin causes loss of hearing sensitivity and frequency selectivity, Carboplatin causes loss of sensitivity, not necessarily loss of selectivity

59
Q

What occurs when positive ions flow into the hair cell?

A

depolarization

Hearing A+P (12 decks)

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