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neuro ch 7
terms
14
Other
Not Applicable
12/14/2005

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Term
impedance
Definition
higher impedance means resists the propagation of sound more
Term
three bones of the inner ear
Definition
malleus, incus, stapes
Term
stapedius muscle
Definition
innervated by cranial nerve VII, pulls the stapes footplate out of the oval window
Term
tensor tympani
Definition
innervated by cranial nerve V, inserts on the malleus and increases the tautness of the ear drum when it contracts
Term
acoustic reflex/attenuation reflex
Definition
activation of the VIIIth cranial nerve causes the tensor tympanmi and staepedius muscle to contract, protecting the ear from very loud sounds
Term
hyperacusis
Definition
ordinary sounds seem much louder than usual, often due to damage of the facial nerve (nerve VII)
Term
helicotrema
Definition
where the scala tympani and scala vestibuli communicate in the cochlea
Term
place coding
Definition
stimulus frequency is coded along the length of the basilar membrane - high frequency waves dissipate quickly, low ones travel to the floppy end of the basilar membrane
Term
endocochlear potential
Definition
inside of the hair cell is about 60 mV neative to the perilymph, or about 140 mV negative to the endolymph bathing the cilia.
Term
outer hair cells
Definition
contain contractile proteins that emphasize the movement of the basilar membrane. positive feedback. "cochlear amplifier"
Term
spontaneous otoacoustic emission
Definition
when the positive feedback system going on in the ear goes wrong, sound comes out of the ear
Term
transient evoked otoacoustic emissions
Definition
a sharp click is presented to an ear, the click rings in the organ of corti for awhile but eventually dies down due to the intrinsic damping properties of the healthy inner ear. TEOAEs normally have a particular frequency distribution that reflects the activation of outer hair cells and the mechanics of the basilar membrane, so looking at it you can tell if a part of the organ of corti has been damaged
Term
anterograde or Wallerian degeneration
Definition
if a nerve is cut, the distal segment (away from the body, towards the terminals) degenerates
Term
retrograde degeneration
Definition
if cut in axon is made too close to cell body, the cell body may die
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