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CMSD6310 Audition l > 2.1 Cochlear Anatomy ll > Flashcards

2.1 Cochlear Anatomy ll Flashcards

1
Q

What cells are also called the rod of corti?

A

Pillar cells

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2
Q

What did experts think occurred at the rod of corti?

A

It used to be thought of as the source of cochlear resonance.

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3
Q

What is the connection between the tectorial membrane and inner hair cell stereocilia? (2)

A

Stereocilia on the OHCs are physically embedded in the tectorial membrane, at least for OHCs.

IHCs, the stereocilia are bent by Henson’s strip and hydraulic coupling.

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4
Q

What is the supporting cell at the top and bottom of the outer hair cell?

A

Deiter cells

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5
Q

Where do hair cells contact the fluid? Which fluid?

A

Only the top surface of the HCs contact the endolymph. The bodies of the HCs are in fluid very similar to perilymph (Corti fluid)

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6
Q

Where are tight junctions located in the organ of corti?

A

Around the tops of the HCs and supporting cells.

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7
Q

What is the primary role of tight junctions located in the organ of corti?

A

To separate endolymph and perilymph.

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8
Q

Where are tight junctions formed?

A

At the level of the reticular lamina.

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9
Q

What is the basilar membrane permeable to?

A

Perilymph.

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10
Q

What structure is located above the hair cells?

A

The tectorial membrane.

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11
Q

What kind of structure is the tectorial membrane (composition)?

A

Gel protein and fibrous structure.

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12
Q

How does the tectorial membrane relate to the outer hair cell and inner hair cell?

A

The stereocilia of the OHCs are physically embedded in the tectorial membrane, but the stereocilia of the IHCs are not.

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13
Q

What direction do the connections of the tectorial membrane make the stereocilia move? When does this occur?

A

In a radial direction (from the modiolus to the lateral wall).
When the BM moves up and down.

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14
Q

What are the two potential mechanisms that cause the bending of IHC stereocilia?

A

The potential mechanisms are Henson’s stripe and hydraulic coupling (vibrations of water—this one is more important).

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15
Q

Which hair cells are supported by the Deiter cells?

A

OHC

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16
Q

Describe what the “fingers” of the Deiter cells do?

A

The fingers go from the bottom of one OHC to the top of another OHC.

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17
Q

What is the freedom of movement like for the outer hair cells?

A

The larger portion of the OHC bodies are free of contact with supporting cells. I.e., free to move

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18
Q

What is the take home point of this image? What is it showing?

A

Deiter’s cells don’t attach to the OHC bodies. It is the fingers of the DCs that go from the bottom of one OHC to the top of another.

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19
Q

What is meant by the mosaic shape as it relates to the hair cells?

A

Each HC in isolated from other HCs thus mosaic shape. Each is surrounded by supporting cells.

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20
Q

What happens if the hair cells die?

A

Hearing loss—if HCs die, they can’t be regenerated.

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21
Q

How do we number the outer hair cells from the inside out?

A

1, 2, 3 from the inside out.

22
Q

What supporting cells participate in making this mosaic shape? (2)

A

The Deiter cells and the outer pillar cells.

23
Q

Where is the stereocilia?

A

The stereocilia are on the top surface of the OC(i.e., on the reticular lamina)

24
Q

What is the difference in shape configuration for the OHC and IHC that we can observe on the reticular lamina?

A

OHC are 3 W-shape rows
IHC are single U straight line.

25
Q

How does the size of stereocilia change?

A

The most lateral is the tallest.

26
Q

How do the OHC and IHC differ in their contact with the sulcus cells?

A

IHCs—fully contacted with SCs. OHCs—largely free of contact with SCs.

27
Q

Why is the changing of shape important for OHC?

A

OHCs are responsible for the amplification of sound by changing shape. Therefore, they need to move freely.
(They are still restricted at the top and bottom. Only the length changes (shape change))

28
Q

What is the shape analogy of the OHC vs the IHC?

A

OHC—cylinder. IHC—vase.

29
Q

Is the OHC lateral wall thick or thin? What is the function of this?

A

OHC lateral wall is thick, which is what allows them to stand up without support of supporting cells.

30
Q

What is at the top and what is at the bottom of OHC? (2)

A

Contact with supporting cells at the top and bottom.
Tight junction at the top and the nuclei at the bottom.

31
Q

What type of neurons innervate the OHC? And which nerve?

A

Afferent: Type II SGNs. 5%
Efferent: Medial efferent.
Nerve: Auditory nerve.

32
Q

Where is there greater efferent innervation for OHC in the cochlea?
(Apex or Base)

A

Greater efferent innervation for the OHCs at the base of the cochlea

33
Q

What is the difference between the cuticular plate and the reticular lamina?

A

Cuticular plate is on top of each HC. Reticular lamina is the plate structure formed by the tops of HCs and supporting cells.

34
Q

Is the IHC lateral wall thick or thin?

A

Thin.

35
Q

Where is the nuclei of the IHCs and the nuclei of the OHC?

A

IHC: middle of the cell.
OHC: bottom

36
Q

Which type of neurons innervate IHC?

A

Afferent: Type I SGNs. Efferent: Lateral efferent

37
Q

Which innervation as it relates to the hair cell (IHC or OHC) is the main ascending info pathway? What about the other one?

A

IHCs- Type 1 SGN = main ascending information pathway from the cochlea to the brain.

The OHCs only synapse with type II SGNs, which we know very little about their functions.

38
Q

What is the major role of the OHC?

A

The major role of the OHCs is to not provide neuronal information pathway, but to provide mechanical amplification.

39
Q

What is the difference (in general and in one sentence) between an efferent and afferent pathway?

A

Afferent pathway: carries information to the brain. Efferent: carries information away from the brain.

40
Q

What is the cochlear innervation as it relates to the efferent and afferent pathway (hint, connect it to the IHC and OHC)

A

Afferent: IHCs to Type I SGNs and OHCs to Type II SGNs
Efferent: Medial efferent to OHCs, lateral efferent to IHCs

41
Q

What are the 4 main parts of the cochlear pathway in innervation (relating to structure).

A

Habenula perforata, Rosenthal’s canal, modiolus, internal auditory meatus.

42
Q

For the efferent pathway of OHC, where do the neurons pass for innervation?

A

The medial efferent fibers to OHCs form a bridge that goes THROUGH the tunnel of Corti.

43
Q

Cochlear duct is ________ at basal turn, OSL is _____ at base.

A

Larger
Wider

44
Q

The tunnel of Corti is supported by _________.

A

Pillar cells (rod of corti)

45
Q

What is the connection between DC and HC? (3)

A
  • DCs are structurally strong
  • Transfer BM vibration to hair cells
  • The finger of DC goes up to other HCs—making
    longitude connection
46
Q

What is the link between the SC and the HC?

A

IHCs: vase shape, fully contact with SCs
OHCs: cylinder shape, largely free of contact with SCs

47
Q

What are 4 characteristics of OHC and their contact with the Sulcus cells?

A

Cylinder shape
Thick lateral wall,
Tight junction at top
Nuclei at bottom
Contact with SC at top and bottom

48
Q

How many layers do OHC have?

A

3, they have that many to help support their body.

49
Q

What is the name of the artery that supplies 80% of the blood in the cochlea?

A

Spiral Modiolar Artery

50
Q

IHC receive about ___ % of the afferent nerve fibers.

A

95%

51
Q

OHC receive about ____% of the afferent nerve fibers.

A

5%

CMSD6310 Audition l (16 decks)

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