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22 Cards in this Set
- Front
- Back
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How are the receptor cells of hearing arranged?
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Either side of Rods of Corti. Single row of inner hair cells on the modiolar side and 3 rows of outer hair cells arranged in a very regular geometric patter on the outer side. The inner and outer cells vary in their shape, arrangement of sterocilla and nerve supplies.
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How many inner hair cells are in each ear? How are they arranged?
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3500; arranged in a single row between the inner phalangeal cells and the inner rods. The basal end of each hair cell is in contact with nerve endings and supportive cells.
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What does the inner cell need?
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Support of the phalangeal cell
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Describe the location of IHC's
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Single row of hair cells lying between inner phalangeal cells and the inner rod of Corti
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What is the shape of the IHC versus OHC
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IHC=droplet shape; OHC=cylindrical like a test tube
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Describe the # of IHC at the base versus the apex of Cochlea
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The number of cells varies along the length of the basilar membrane. There are about 80 inner hair cells per millimeter at the basal end and 115 per mm at the apical end.
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What are receptor/sensory cells?
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Hair cells
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What are the 4 main components of a inner hair cell
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Cell body, cuticular plate/cuticle, kinocilium & basal body; steriocilia
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Describe Cell body of inner hair cell
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Contains cytoplasm, nucleus, cell membrane. Cell body height remains fairly constant throughout the cochlea (however stereocllia height does vary)
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Describe the cuticular plate of IHC
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Caps the hair cell at the apex of the cell. Bears the sterocilia. There is a notch in the plate where a kinocilium was at one time, only a structure called the basal body remains on the modiolar side of the cell (just beneath a cutical-free region of the cell surface) and is surrounded by an aggregate of granular material.
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Describe the characteristics of the stereocilia of the IHC
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-Attached to the top of the cuticular plate, 2 wavy rows that are parallel to the axis of bm/cochlea.
-vary in length and diameter. Outer row of sterocilia is the longest (also true in OHC); cilia are also longest toward the apex -Stiff and resilient. Also, IHC are coarser than OHC. 48 stereocilia per hair cell. |
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Describe the composition of the stereocilia of the IHC/ how they are connected. How is it they move together?
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Each cilium has a marked constriction at its base and a rootlet that penetrates into the cuticular plate. The cilia are joined by bridges of very fine fibrils so that all the cilia on one cell tend to move together as a unit, when the longest ones are bent.
The sterocilia are also connected sideways by links that run parallel to the cuticular plate. These links run between the stereocilia of the same row as well as between the tereocilia of different rows. This also causes them to move together. |
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How many OHC in each ear?
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13, 500
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What are OHC covered with?
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Well-defined plasma membrane
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What do OHC's have that IHC's don't?
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Motility
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What is actin?
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Contained in the cilia, a protein that has something to do with their ability to actively change mechanical properties and motility
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What properties do inner and outer hair cells share?
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Capped with cuticular membrane from which a # of stereocilia protrude, rising above the reticular membrane; Contain a basal body; Entire cell and its cilia are covered with a well-defined plasma membrane.
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What are OHC supported by?
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Dieter cells, don't come up as far on teh sides as the inner phalangeals of the IHC's
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What do OHC's respond primarily to?
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Lateral/radial shearing
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Describe the # rows of OHCs from the base to apex of cochlea
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3 rows of OHCs near the base; and up to 5 near the apex.
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Length/variation of cilia in OHC
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Cilia are longer at the apex and shorter at the base. They are also longer on the outside than the inside.
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How are OHC rows arranged (shape)
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Rows of stereocilia form a V or W, with the base of the W directed toward the spiral lamina. The angle of the W, which is wide at the basal turn, becomes increasingly acute toward the apex of the cochlea.
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