The Biological Foundations of hearingThe EArHearing MechanismParts of the EarOuter Ear- Main StructuresOuter Ear- FunctionsMiddle EarHealthy EardrumMiddle Ear- FunctionsMiddle ear- FunctionsMiddle Ear- FunctionsAcoustic ReflexReviewInner EarInner EarInner ear- CochleaAcoustic NerveAuditory PathwaysPhysiology of HearingSlide 2001/14/191Sound enters our ear and is modified to sound energy and transmitted to the brainOur brain processes and interprets sound energyWe hear with our brains, not our ears!Video of process:http://science. education.nih.gov/supplements/nih3/hearing/activ ities/lesson4.htm01/14/1925 sections1. Outer ear2. Middle ear3. Inner ear4. Acoustic nerve5. Brain’s auditory processing centers01/14/193Outer EarMiddle EarInner Ear01/14/194Pinna – visible portion of the earCanal – connects pinna with eardrumCerumen – waxy substance found in ear01/14/195Pinna -a sound collectorCanal -protects the tympanic membrane (eardrum) and enhances sound pressure01/14/196Tympanic membrane (eardrum)OssiclesEustachian tube01/14/19701/14/198Acts as a transformer by boosting the pressure of sound energy to inner earTympanic membrane – (eardrum)Forms airtight and sterile seal to middle earThin, flexible, responsive to sound wave energy01/14/199Ossicles – three tiny bones in middle ear Malleus (hammer) Incus (anvil)Stapes (stirrup)The ossicles work together to boost and transmit pressure to inner ear01/14/1910Eustachian tube Connects middle ear to pharynx (back of throat)Opens with each swallowMaintains equal pressure between middle ear and outsideAllows drainage of fluid from middle ear01/14/1911Two muscles in the ear provide protection against extremely loud noisestensor tympani - tenses the eardrum to lessen vibrationstapedius - stiffens the ossicular chain01/14/1912Name the part of the ear given its function:Drains fluid from the middle earEar drum protectionTransmit sound from the ear drum to the inner earCollects sound and funnels it into the ear canalPressure equalizerProvides protection of the middle earProvide protection against extremely loud sounds01/14/1913Converts energy to a code which can be interpreted by the brainOval windowCochleaEndolymph 01/14/1914Oval window - small opening in the cochlea that connects to the footplate of the stapesCochlea - snail-like organ containing hair cells and …. Endolymph - fluid that fills the cochlea01/14/1915Basilar membrane - floor of the cochleaOrgan of Corti - contains hair cells, called cilia, which respond to movement of the endolymphHair cellshttp://youtu.be/U_HUgzhmq4U 01/14/1916Acoustic nerve- carries neural impulses to the brain. Two divisions:vestibular division - transmits information from the semicircular canals for balanceauditory division - transmits information from the cochlea for hearing01/14/191701/14/1918The tympanic membrane and ossicular chain vibrate in response to incoming sound wavesThe footplate of the stapes moves against the oval window causing movement of the endolymph in the cochleaThe hair cells (cilia) on the basilar membrane of the cochlea move as the endolymph moves01/14/1919The movement of the hair cells creates signals which are translated into nerve impulsesThe nerve ending of the auditory division of the acoustic nerve picks up the impulses and transmits them to the brainJourney into the
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