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How does the ME overcome the impedence mismatch?
1. areal ratio (17:1)
2. curved membrane ratio (2:1)
3. ossicular lever ratio (1:3:1)
Total transmission ratio of the ME
46:1 (46 times more pressure ant footplate than at TM)
=33 dB gain
at 80-90 db, stapedius and tensor tympani have what?
bilateral, consensual reflexive contraction
-they attenuate sound by 10-30 dB
-begins with vascular spongiosis, eventually replaced with sclerotic plaques
-stapes becomes fixed in oval window
-an early sign is Schwartze's sign (bluish-red tint near promontory due to increased vascularization)
-characteristic notch at 2000 Hz (carhart's notch)
-broken ossicular chain
-causes decreased impedance
TM can vibrate freely
central core of cochlea that eventually becomes CN VIII (has nerve fibers from the hair cells and blood vessels)
ductus reuniens of hensen
how scala media communicated w/the vestibular portion of the inner ear (at the basal region)
-is ceiling of organ of corti
-separates endolymph from cortilymph (similar to perilymph)
-cilia penetrate the reticular lamina so they can bathe in endolymph (the rest of the hair cell bathes in perilymph)
the cell bodies of the OHC and IHC neurons comprise the ______________
spiral ganglion of the primary auditory neuron
vestibular (endolymphatic) aqueduct
-from vestibule to endolymphatic sac
-helps regulate endolymphatic pressure to over or under-absorb endolymph
from basal cochlea (scala tympani) to subarachnoid space
-allows transfer of CSF
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