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Still Chapter 17 Hearing & Balance. HEARING 3 main parts of the ear: Outer Ear Middle Ear Inner Ear

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Text of Still Chapter 17 Hearing & Balance. HEARING 3 main parts of the ear: Outer Ear Middle Ear Inner Ear

  • Still Chapter 17

    Hearing & Balance

  • HEARING3 main parts of the ear:Outer EarMiddle EarInner Ear

  • Outer EarPinna = outside portion of the ear, focuses sound waves on the eardrum (tympanic membrane)External auditory canal = ear canal, leads to the eardrum, contains ceruminous glands that secrete earwax

  • The eardrum separates the outer and middle ear

  • Middle EarSound vibrations from the eardrum pass to auditory ossicles (three tiny bones malleus/hammer, incus/anvil, & stapes/stirrup) which transmit sound to the inner earEustachian tube connects to pharynx, allowing air pressure to equalize on both side of the eardrum; can be blocked by infections

  • The Inner EarCochlea filled with fluid picks up vibrations from middle ear which cause hair cells in cochlea to bend Movement of hair converts vibrational energy into nerve impulses

  • Auditory PathwayVestibulocochlear nerve VIII takes the information to medulla oblongata and then to auditory cortex in the temporal lobe

  • Sound Levels of Common NoisesSafe rangeRisk rangeInjury range

    Sound IntensityNoise Source60 dbNormal conversation, bird song80 dbHeavy traffic, ringing phone85 90 dbMotorcycle, snowmobile90 dbHair dryer, lawn mower95 105 dbHand drill, bulldozer, spray painter110 dbChain saw120 dbAmbulance siren, rock concert140 dbJet engine at takeoff165 dbShotgun blast


  • Semicircular Canal in Inner Ear

    Maintain balance and equilibriumFilled with fluid and hair cellsWhen you tilt your head, fluid and hair move and stimulate nerve cells to carry info to cerebellum

    Outer EarPinna & external auditory canalMiddle EarAuditory ossicles (malleus/hammer, incus/anvil, stapes/stirrup)Inner EarVestibule, semicircular canals, cochlea

    Tympanic membrane (eardrum) separates the outer & middle ear

    Eustachian tube middle & inner ear

    Earwax keeps dust, insects, and other foreign materials from entering deeper into the earMalleus, incus, stapes = hammer, anvil, and stirrup (latin translation) smaller than an orange seed (all together)Changes in air pressure affect eardrum eardrum may bend in response to altered air pressure and then pop back to its original position when the eustachian tube opens and internal and external pressure is equalizedVestibule connects the cochlea and semicircular canalsWhen dizzy after spinning, after you stop your brain is receiving conflicting signals since the fluid in your semicircular canals is still moving and telling the brain that you are still moving