1. Sensory System
Ear: Sound & Balance

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
Auris latin for ear
Pinna is external portion of the ear (pinna latin for wing or fin)

4. Outer Ear: External Auditory Canal
Extends from Pinna to eardrum
Fx: Transmits sound waves
Aka ear canal. AKA external auditory meatus.
Adults ~ 2.5 cm in length and .7 cm diameter

5. Outer Ear: External Auditory Canal
Produces Cerumen (earwax)
Fx: Traps foreign bodies
Wet type dominant, dry type is recessive
Cotton swaps = bad, impact wax, can cause damage to your ears.

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:
ruptured

9. Inflammation of the middle ear
Otitis Media
Painful ear infection, bacterial or viral. Usually prescribed antibiotics
Inflammation of the middle ear

10. Components: Ossicles – 3 bones Fx: Mechanical vibration
Malleus (Hammer)
Incus (Anvil)
Stapes (Stirrup)
Fx: Mechanical vibration
Ossicle means small bone

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. Adjusts pressures between middle ear & outside Drains middle ear
Eustachian Tube
Fx:
Adjusts pressures between middle ear & outside
Drains middle ear
Picture – as it opens to nasopharynx

17. Swallowing & yawning open it
Eustachian Canal
Normally closed
Swallowing & yawning open it
Tympanic membrane will not vibrate well if pressures not equal
Fluid in canal behind ear drum

18. If fail to open, increased pressure (pain) and infections
Eustachian Canal
If fail to open, increased pressure (pain) and infections
Fluid in canal behind ear drum

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

20. Bony Chambers (fluid-filled)
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
Bony labyrinth contains perilymph

23. Inner Ear Membranous Labyrinth
Sac contains thick fluid = Endolymph
Membranous labyrinth contains 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
Organ of corti is only found in mammals.
Endolymph
Organ of Corti

26. Organ of Corti Contains specialized hearing receptors or hair cells
Embedded in basilar membrane
Basilar membrane stiff structure separates two tubes in cochlea

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)

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

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

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

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

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

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

37. Crista Ampullaris
Membranous semicircular canals contain crista ampullaris

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

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

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