Download EAR AND HEARING Resonant Frequencies of pinna and EAM are

EAR AND HEARING
Resonant Frequencies of pinna and EAM are
1500-8000 Hz
Tympanic Membrane
3 tissue layers
outer: epithelial
intermediate: fibrous
inner: mucous
Portions of the
Ossicles
Anterior Crus (Crus Anterius)
Base (footplate)
Structures of
the Middle Ear
Ossicles
Middle Ear Mechanism
Impedance (resistance to flow of energy) matching device
Increases pressure of signal arriving at cochlea
25dB gain between TM and OW due to area ratio
lever advantage of ossicles provides a 2dB gain
Inner Ear
Semi
Circular
Canals
Cochlea:
Tonotopic
Arrangement
-Low frequency
processed at
apex, high at
apex
-Modiolus
Organ of
Corti
Traveling wave
Shearing Force
Traveling Wave
• Initiation caused by compression of the fluid in
the scala vestibuli which is transmitted directly to
the basilar membrane
• Point of maximum excursion of BM determines
fx information transmitted to brain
• BM quickly damps after reaching maximum
excursion
• Fx analysis of BM determined by stiffness,
thickness and width of membrane
– Stiffer, thinner, narrow at base
Outer and
Inner
Cells Of
Organ of
Corti
Many nerve cells innervate each inner hair cell, excitation from
fluid flow and turbulence of endolymph
Many outer hair cells are innervated by one nerve fiber,
excitation from shearing effect on cilia
VIII Cranial Nerve: Vestibular and Cochlear
CN: tonotopic representation in tuning curves
SOC: localization of sound in space
IC: inhibition response, time and intensity sensitivity
MGB: relay to the cortex
HG: full tonotopic map
CC: receives stimuli from contralateral ear via ipsilateral MGB