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NROC64H3 (81)
Chapter 11

Chapter 11.docx

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Matthias Niemeier

Chapter 11The Auditory ad Vestibular System 375 418Introduction2 systems that have different functions but have similar structures and mechanisms 1 Auditionhearing 2Vestibular Systembalance internalized process that informs where and how we moveHearing is important while balance is something we rarely think ofThe Nature of SoundSounds are audible variations in air pressure almost anything can move air moleculeswhen objects move toward patch of air it compresses airincrease density of molecules produce variationsFrequencyof sound is number of compressed patches of air that pass by earshertzHz number of cyclessecond Whether sound is perceived high or low or pitch is determined by frequencyIntensity Difference in pressure bw compressed and rarefied patches of air sound intensity determines the loudness we perceiveloud sounds have higher intensityBox 111 Of Special Interest Ultrasound and Infrasoundp378The Structure of the Auditory SystemVisible part of ear has cartilageskin funnel called pinna Latin wingcollects sound from wide area more sensitive to sound form aheadAuditory canalentrance to internal earTympanic Membraneeardrum series of bone connected to medial surface is ossicles Latin Little bones nd Ossicles transfer movement2 membrane called oval window has cochleacontains apparatus for transforming physical motion of oval window membranePinna to tympanic membraneouter earTympanic membrane and ossiclesmiddle earApparatus medial to oval windowinner earNeural response to sound from inner eartransfer and process in brain stem thalamusmedial geniculate nucleusMGNprimary auditory cortexA1temporal lobe The Middle EarVariations in air pressure are converted into movement of ossiclesComponents of the Middle EarComposed of tympanic membrane ossicles and 2 tiny muscles that attach to ossiclesConical w cone extending into cavity of middle ear3 ossicles 1 Malleus Hammer 2 Incus AnvilForm rigid connection w Malleus 3 Stapes StirrupForm flexible connection w incus flat bottom portion of stapes the footplate moves in and out like piston at oval window to transmit sound vibrations to fluid of cochleaAir in middle ear is continuous w air in nasal cavities via Eustachian tube usually closed by valveSound Force Amplification Sound waves move tympanic membrane and ossicles move another membrane at oval windowPressure on membraneforce pushing it surface area will be greater at oval window than tympanic membrane if 1 Force of oval windowforce of tympanic membrane 2 Surface area of oval windowsurface area of tympanic membraneForce is greater at ossicles act like levers small by stronger vibrations sa is smaller at oval window The Attenuation ReflexTensor tympani muscle is anchored to bone in cavity of middle ear at 1 end and attaches to the malleus at other endStaedius muscle extends form fixed anchor of bone and attaches to stapesWhen muscles contract chain of ossicles becomes rigid and sound conduction is greatly diminishedAttenuation reflex Onset of loud sound triggers neural response to cause muscles to contractMay help with allow ear to adapt to continuous sound at high intensities protect inner ear form loud noises to prevent damageThe Inner EarInner ear comprised of cochlea and labyrinth part of vestibular systemAnatomy of the Cochlea Cochlea Latinsnail has spiral shape hollow tube is made of boneCentral pillar of cochlea is modiolus
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