deck_643653 Flashcards
Impedance mismatch
water has much higher impedance than air -> problem for transferring sound from middle ear to inner earovercome with mechanical advantage
mechanical advantage of ear
- small surface area of oval wind to large area of tympanic membrane2. lever action of ossicles
range of human hearing
20-20000 HZ
Frequency discrimination
place theory: high frequency displace base of basillary membrane and low frequency displace apex -> different hair cells depolarizedfrequency theory: frequency of sound causes similar frequency of afferent nerve discharge (only works for low frequencies)
Weber Test results
heard in good ear = nerve deafnessheard in bad ear = conductance deafness
How membrane potential across organ of Corti
hairs of hair cells bathed in endolymph (+90mV) basilateral surface bathed in perilymph (-90mV)allows for depol and hyperpol of hair cells
how depolarization and hyperpolarization of hair cells
stereocili toward kinocilium - depolarizationstereocilia away from kinocilium - hyperpolarization
sound transduction
sound wave enter external ear -> external auditory meatus -> vibrates tympanic membrane -> vibrates ossicles -> stapes displaces oval window -> displacement of perilymph in scala vestibuli -> vibration of organ of corti -> displacment of basilary membrane -> shear force of cilia on hair cells -> open channels -> K+ influx -> depol -> afferent cochlear signal
endolymph
in scala mediahigh K+ content and low Na
perilymph
in scala vestibuli and tympanihigh Na content and low K
inner hair cells
more afferent nerve fibersauditory recepter and sends signal
outer hair cells
amplifies and fine tunes signal
semicircular canals
detect angular or rotational acceleration of headsensory portion in ampull (cupula over hair cells)
Utricle
gravity in upright position (linear acceleration)otoliths over hair cells
saccules
gravity in prone positionotoliths over hair cellsrespond to head movement of all directions
