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Ear: Sound & Balance

Ear: Sound & Balance. Sensory System. 3 Parts : Outer – Middle - Inner. Outer Ear: Auricle. Called the Pinna Fx : Collects sound waves Visible part of the ear, outside the head. Outer Ear: External Auditory Canal. Extends from Pinna to eardrum Fx: Transmits sound waves.

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Ear: Sound & Balance

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  1. Ear: Sound & Balance Sensory System

  2. 3 Parts: Outer – Middle - Inner

  3. Outer Ear: Auricle • Called the Pinna • Fx: Collects sound waves • Visible part of the ear, outside the head

  4. Outer Ear: External Auditory Canal • Extends from Pinna to eardrum • Fx: Transmits sound waves

  5. Outer Ear: External Auditory Canal • Produces Cerumen (earwax) • Fx: Traps foreign bodies

  6. Middle Ear: • Air-filled • Converts sound waves to mechanical energy • Amplifies it • Conducts to next chamber

  7. Components: • Tympanic membrane – Eardrum • Vibrates • Sound to Mechanical Energy

  8. Perforated Eardrum:

  9. Otitis Media • Inflammation of the middle ear

  10. Components: • Ossicles – 3 bones • Malleus (Hammer) • Incus (Anvil) • Stapes (Stirrup) • Fx: Mechanical vibration

  11. Middle Ear: Ossicles

  12. Ear Ossicles

  13. Middle Ear: • Oval window - Tranfers mechanical vibration from middle ear to inner ear

  14. View of OVAL WINDOW Oval Window

  15. Middle Ear opens to Nasopharynx via Eustachian tube

  16. Eustachian Tube Fx: • Adjusts pressures between middle ear & outside • Drains middle ear

  17. Eustachian Canal • Normally closed • Swallowing & yawning open it • Tympanic membrane will not vibrate well if pressures not equal

  18. Eustachian Canal • If fail to open, increased pressure (pain) and infections

  19. Requires Ear Tubes – drain the excess fluid & prevent infection

  20. Inner Ear • Bony Chambers (fluid-filled) • Vestibule • Semicircular Canals • Cochlea

  21. Inner Ear Bony Labyrinth

  22. Inner Ear Bony Labyrinth • Fluid-filled = Perilymph • Membranous sac is suspended in the periliymph = Membranous labyrinth

  23. Inner Ear Membranous Labyrinth • Sac contains thick fluid = Endolymph

  24. Hearing and the Inner Ear - Cochlea • Snail-like shape • Membranous sac contains organ of Corti

  25. Cochlear Ducts Membranous labyrinth Perilymph Endolymph Organ of Corti

  26. Organ of Corti • Contains specialized hearing receptors or hair cells • Embedded in basilar membrane

  27. Organ of Corti • Hair cells covered by gel membrane (Tectorial membrane) • Corti converts mechanical energy into electrochemical energy

  28. Hearing Process • Ossicles vibrate oval window • Sets the fluids into motion (pressure waves)

  29. Hearing Process • Vibrate basilar membrane • Hair cells rub tectorial membrane (bent)

  30. Hearing Process • Hair cells transmit impulse to cochlear nerve • Interpretation of sound in temporal lobe

  31. Sound Energy to Hearing Interpretation Sound Energy Mechanical Energy Mechanical  Electrochemical

  32. Balance: Static Equilibrium • Position of head when not moving (which way is up) • Membranous sacs in vestibule contain maculae

  33. Maculae Physiology • As head moves, otoliths roll in response to gravity • Pulls on gel and bends hairs in receptors

  34. Maculae Physiology • Hair cells send impulse via vestibular nerve • Signal to cerebellum for interpretation

  35. Balance: Dynamic Equilibrium • Rotation of head or movement is detected • Membranous semicircular canals filled with endolymph

  36. Crista Ampullaris • Membranous semicircular canals contain crista ampullaris

  37. Crista Ampullaris • Contains receptor cells (w/ hairs) embedded in cupula (gel-like cap)

  38. Ampullaris Physiology • When head moves, endolymph lags behind • Cupula drags against endolymph current and bends hairs

  39. Ampullaris Physiology • Stimulates hair cells to send impulse • Vestibular nerve sends impulse to cerebellum

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