1. Cochlea
Hearing

2. Cochlea spiral chambers coils around a bony pillar - modiolus
running through center of coils like a wedge shaped worm is cochlea duct (scala media)
it plus a shelf like extension of modiolus divides the cavity into 3 regions

4. cochlear duct scala vestibuli scala tympani
scala vestibuli - superior
continuous with vestibule and abuts the oval window and the scala media or cochlear duct
scala tympani – inferior
which ends in round window
scala tympani

5. cochlear duct scala vestibuli vestibular membrane scala tympani
endolymph
perilymph
both the scala vestibuli and scala tympani have perilymph
vestibular membrane - “roof” of cochlear duct
thought to secrete endolymph
vestibular membrane
scala tympani
perilymph

6. the “floor” is cochlear duct and basilar membrane, which supports the organ of Corti

9. A branch of the cochlear nerve (joins vestibular nerve to form vestibulocochlear nerve) runs from the organ of Corti, through the modiolus → brain.

10. Vibrations from oval window → perilymph → basilar membrane

11. Vibrations from oval window → perilymph → basilar membrane
scala
vestibuli
Organ of Corti
scala
tympani

12. When maximum vibrations occur, the organ of Corti hair cells are pulled by attached “awning” – tectoral membrane.

14. When maximum vibrations occur, the organ of Corti hair cells are pulled by attached “awning” – tectoral membrane.

15. Their movement causes ion channels in hair cell membranes to open.
Neurotransmitters are released and nerve endings below hair cells are stimulated.

16. Cerebral cortex “processes” sounds.

17. hair cells nearest oval window = high pitch
near cochlear apex = low pitch
amplitude = more hair cells in the area are vibrated

18. Sound Pathway

19. Tympanic Membrane Auditory Canal
What is the scientific name for ear wax?
cerumen
Tympanic Membrane
Auditory Canal
Pinna
Collects
sound
Transmits vibrations

20. Tympanic Membrane Auditory Canal
What is its function?
Trap foreign objects
Tympanic Membrane
Auditory Canal
Pinna
Collects
sound
Transmits vibrations

21. Malleus Incus Stapes Amplifies vibrations Ossicles
What prevents the eardrum from rupturing?
Ossicles
Tensor tympani muscle tightens ossicles
Malleus
Incus
Stapes
Amplifies vibrations

22. Malleus Incus Stapes Amplifies vibrations Ossicles
What is the function of the Eustachian tube?
Ossicles
Equalizes pressure between middle ear and throat
Malleus
Incus
Stapes
Amplifies vibrations

23. What is behind the stapes?
Oval Window

24. What is behind the oval window?
Perilymph

25. Vestibular membrane
Basilar membrane

26. Endolymph Vestibular membrane Endolymph Organ of Corti
Basilar membrane
Endolymph

27. Tectorial membrane
Hair cells

28. Hair cells scrape against the tectorial membrane.

29. Action Potential
Cochlear Nerve

30. Vestibulocochlear Nerve Cerebral (Auditory) Cortex
Of Brain