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SLHS 309 Study Guide Exam 3

by: Lauren Schmidt

SLHS 309 Study Guide Exam 3

Marketplace > Purdue University > SLHS 309 Study Guide Exam 3
Lauren Schmidt
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This 27 page Study Guide was uploaded by Lauren Schmidt on Thursday February 5, 2015. The Study Guide belongs to a course at Purdue University taught by a professor in Fall. Since its upload, it has received 102 views.


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Date Created: 02/05/15
The Amazing Outer Hair Cell SLHS 215 Mammalian Hearing Mammals have a better sense of hearing than other vertebrates The cochlear a 77 A positive feedback loop in the cochlea that D the traveling wave 13115 httpwwwiurcmontpinsermfrcric51lauditionengIishcortiinnervschinervjpg 2 Organ of Corti Hair bundle Outer hair cell Inner hair cell Bas ar Afferent quot point membrane E erent Osseous spiral lamina 13115 httpwwwnaturecomnrnjournaIv7n1imagesnrn1828f2jpg 3 Outer Hair Cell Test tube shaped Sits on a cup formed by a supporting cell a rows about 12000 Stereocilia 6 7 rowsarranged in a a Inner Ear Inner Ear Outer Hat Cell Stereoax39a Comea Structure H3 691939 OHC Structure ENDO LY MPH n Nucleus closer to the base of 1 the cell Synaptic vesicles 6 Contain neurotransmitter l Nerve ber endings at the base Greater number of a bers 3 at the top PERI LYMPH 13115 OHC What is Unique Similar to a a rather than a sensory cell Contain motor proteins that make muscle cells contract 0 Actin myosin prestin in stereocilia and cell wall Allow OHC to shorten in a C pquot 939 ii 2Z iii3i22 response to sounds Electromotility 13115 httpwwwnaturecomnrnjournav7n1imagesnrn1828f5jpg 6 OHC What is Unique IVIost cells have an internal quotskeletonquot like a scaffold Called the D Maintains cell39s shape keeps cell quotstiffquot Protects organelles within the cell OHC do NOT have a central cytoskeleton Improves the cell 5 D no 13115 7 OHC What is Unique Pressurized cells are found in quot D but rarely found in animals quot OHC are pressurized like the tube in a bicycle tire Normal fluid pressure 9 fluid pressure flUId pressure 13115 8 httpswww bcmeduheaIthcarecarecentersotolaryngologypatientinformationhowear worksouter hairceIIpressurized Outer Hair Cell 50 150 stereocilia per OHC OHC length D along length of cochlea longitudinal axis 160 40 10 25 05 015 0037 13115 FREQUENCY kHz More Unique Aspects Hair cells do not use a chain of D reactions like other sensory cells They have a much faster mechanical process A spring that opens ion channels very quickly when the stereocilia bend The springs are called D 13115 1 LA A a Vm andus A at r 1H rm J 7 ger wJJ v 3 7 quot 9 WWW httpMMNhhmior sensesc130htm 13115 Tectorial Reticular membrane lamina Stereocilia bending out Stereocilia Modiolus gt R l A fir 1 Outer v1 hair cells quot Inner hair cells R J Basilar membrane deflected up I v Basilar Rods of A membrane Corti B Endolymph Reticular Perilymph lamina Voltagegated a calcium channel Stereocilia bending in Vesicle filled with excitatory neurotransmitter Spiral ganglion neurite Basilar membrane deflected down httpwhatwhenhowcomwpcontentuploadsZO1204tmp15F71jpg 12 Cochlear Mechanics Passive properties Changes in mass and stiffness along the length of the cochlea Base responds to a sounds traveling wave crests Apex responds to a sounds 200 Hz 100 Hz 50 Hz 25 Hz Helicotrema 13115 30lmml Cochlear Mechanics Passive mechanics cannot explain the very ne sound discriminations humans can make The cochlear ampli erquot or a quot senses and increases ampli es the vibrations within the Organ of Corti HOW W cetrode SunnuKMng t eumppoe a m 4 Vquot 39I lt quotV inner haor 0H Kathi 39l Itr ro l 1 II I Outer Mir cdls ISound 13115 14 Cochlear Active Process Thought to be from the OHC Using the motor proteins And via the a feedback loop OHC change their D in response to sounds Motility or electromotility Sharpens and ampli es the peak of the traveling wave on the BIVI D 13115 15 13115 motor proteins motor proteins expanded compressed 13 membrane normal response with motor proteins response during drug treatment without motor proteins 1 base 1 A d 16 Cochlear Function The normal auditory system has D frequency selectivity dynamic range 0 Sensitive thresholds All thought to be related to the cochlear ampli cation based on OHC motility 13115 17 From HC to Nerve Transduction Conversion of D from one form to another HC convert D BIVI movement To electrical impulses to be carried by the AN 13115 18 Auditory Nerve Organization HF and LF bers HF from HC at the c of the cochlea Outer perimeter bers LF from HC at the a of the cochlea Inner core bers D organization is preserved in the nerve And throughout the auditory pathways 13115 19 Auditory Nerve Afferent and efferent bers lVIost afferent fibers innervate the a D send information up the auditory nerve lVIost efferent fibers innervate the D 5 receive feedback to modulate signals A erents point lllll nbrane E erent Osseous spiral 13 115 11457 lamina 20 Auditory Nerve Activation 13115 Auditory Nerve Generates action potentialsquot Allornone potentials Always the same amplitude Called D a Spontaneous activity Random nerve ring with no stimulation Threshold Lowest level at which ring spontaneous ring rate above Level at which neuron starts responding quothears sound 13115 22 Coding Intensity Auditory Nerve Soft sounds Low spike rate Loudersounds Increase in spike rate Rate codequot I Evenloudersounds Increase in the number of 13115 E2 responding 140 120 a 100 80 60 40 20 l l l l 20 40 60 80 100 intensity dB SP1 r amount of neu m activity I s l s I s s s s s s x 7 characteristic frequency Frequency Coding Place code Place of crest on BIVI LFs at the D HFs at the D Also individual HC5 and nerve bers are tuned to speci c frequencies 13115 nitude dB SPL n lulus mag 00 30 60 40 24L D Temporal Coding Nerve bers phaselock to the a of the signal Sound freaency is coded by 1 i JA A A 1 A A a J V Lquot J v J r l Jc L P J rt a A39l 3939 lbquot 39 quotvquot quotv 39v vquot V U lowfrequenc y sound wave response phase locked on every cycle the of the nerve ber discharges For higher frequency sounds Individual bers phaselock gt at different moments The collective response of the bers corresponds to the period of the signal highfrequency 13115 q n A 2 f 1 5 A A 1 f a a u u U U j u u u U v u U u V Ound 9 l l l L l l l l l L l L l t I q l l l l l l l J l A j A j individual i 39 fHMe J l 1 l A 1 responses 1 l l l l I I l t I l l r total lHl H Ml UH 1m lMl Hquot M 1m lHl HH Hl 1m ll couecnve MD actmty 25 Tuning Curve 100 Plots threshold for each frequency of stimulation Audiogram of nerve ber Sounaneveu at ear drum dB SPL 50 Determines Best I of the nerve ber Frequency at which ber responds most easily 0 a area of the nerve ber Area within which a signal will evoke a response from the ber Frequency kHz 13115 26 The cochlea rocks httpwwwyoutubecomwatchvX09wauYrRo 1 Brownell et 211 1985 httpWWWphysi01uclacukashm0re


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