presentation topic is from physiology

2. ANMOL JILANI

3.  Cochlea is a system of coiled tubes.
 It consists of:
 Three tubes:
1-Scala vestibuli.
2-Scala media.
3-Scala tympani.

4.  Two membranes:
1-Reissners (vestibular
membrane).
2-Basilar membrane

5. o Perilymph:
 Present in scala vestibuli
and scala tympani.
 Almost identical to CSF.
o Endolymph:
 Present in scala media.

6.  Contains 20,000 to 30,000 basillar fibers.
 These fibers are stiff,elastic,reed-like
structures that are fixed at their basal ends
in the center of cochlea (modiolus)but not
fixed at their distal ends.

7.  Length:
 The lenghth of the basilar fibers increase progressively
from the base of cochlea to its apex.
 Diameter:decreases from base to apex of cochlea.
 Frequency:
Base :high frequency.
Apex :low frequency.

8.  If the foot of stapes moves inward.
 The round window bulge outward
instantaneously because the cochlea
is bounded on the sides by bony
walls.
 Therefore,the initial effect is to
cause the basilar membrane at the
very base of the cochlea to bulge in
the direction of the round window.

9.  however,the elastic tension that is built up
in the basilar fibers as they bend toward the
round window initiates a wave that travels
along the basilar membrane toward the
helicotreama.

10.  High frquency sound wave.
 Medium frequency sound wave.
 Very low frequency sound wave.

11.  Lies on the surface of bassilar membrane.
 Contain mechanically sensitive hair cells
which are receptive end-organs and generate
nerve impulses in response to sound
vibrations.

12. Inner hair cell.
Outer hair cell.
Depolarization.
Hyperpolarization.

13.  Stereocilia
 Direction toward the longer one
 Rapid K influx to tips of the stereocilia
 Depolarization of cell membrane
 Basilar fiber to scala vestibuli ………
depolarization
 Endocochlear Potential
 Perilymph (Na, K )
 EndoLymph(K, Na )
 +80mv diff. all the time