1. The Inner Ear SPA 4302 Summer 2006

2. Two Halves: ____________--transduces motion and pull of gravity ____________-transduces sound energy (Both use Hair Cells) INNER EAR Sensory Endorgans encased within very dense bone

4. Subdivision into spaces containing ___________ (blue), and spaces containing __________ (red)

5. Cochlea is Divided into 3 “Scala” Scala Vestibuli –__________ Membrane Scala Media –__________ Membrane Scala Tympani ___________ - the opening between 2 outer Scala

6. Fluids filling the Inner Ear ___________- in S. Vestibuli and S. Tympani –High Sodium / Low Potassium concentrations –Low Voltage (0 to +5 mV) ___________- in S. Media –High Potassium / Low Sodium concentrations –High Positive Voltage (85 mV)

7. Cross-Section of the Cochlea Third Turn Second Turn First Turn

9. A Cross Section Shows the 3 Scala

12. Within S. Media is the Organ of Corti

14. I = Inner Hair Cells P = Pillar Cells O = Outer Hair Cells D = Deiter’s Cells

15. The Stereocilia on IHCs and OHCs ________ (at top) V or W shaped ranks ________ (at bottom) straight line ranks

16. Stereocilia bent toward tallest row ________ flows into cell Voltage shifts to a less __________ value More neurotransmitter is released

17. Cochlear Afferent (Sensory) Neurons __________ (95%) –synapse w/ IHC –1 IHC to 20 neurons –well myelinated __________ (5%) –Synapse with OHCs –Many OHCs to 1 neuron –unmyelinated

18. Cochlear Functions __________- Converting acoustical- mechanical energy into electro-chemical energy. ___________- Breaking sound up into its component frequencies

19. Development of the Inner Ear ________________Beginning in week 3, ________________ develops, _______________Invaginates to form _______________, _________________Which then closes off, leaving an _________________.

20. Capsule divides into saccular, utricular divisions –________: cochlea (begins forming in week 6) –________: semicirc. canals, endolymphatic sac & duct Organ of Corti forms from week ___ Inner ear fully formed by ___ weeks

21. Hearing Loss and Disorders of the Inner Ear Vast majority of SNHL results from inner ear disorder. ____________.Cochlear pts often hear, but cannot distinguish what they hear very clearly: ____________. –Arises from frequency and other distortions associated with changes in inner ear function.

22. Inner Ear Disorders: Prenatal Causes Genetic mutation/inheritance Cytomegalovirus (CMV) __________ Rubella Rh incompatibility __________

23. Anatomical Anomalies Often seen as Bony malformations Examples: Mondini (incomplete cochlea) Enlarged Duct (shown here)

24. Age Effects

25. Noise Damage Temporary Threshold Shift (TTS) Permanent Threshold Shift (PTS) Duration, Timing and Intensity influence Typical “Noise Notch” often seen between ____________ first. Notch widens and deepens over time, with hearing loss spreading to adjacent frequencies, and increasing in degree.

26. Ototoxicity Substances poisonous to the ear Medicines –___________ antibiotics –___________ drugs for CA –___________ Industrial Chemicals (tolulene, etc) May affect __________ Degree of hearing loss varies Synergy with noise or other ototoxic agents

27. Meniere’s Disease Really a Syndrome: –_________ Vertigo –Roaring, Low Freq. Tinnitus –Fluctuating ___________ Hearing Loss –Sensation of Aural Fullness ____________________Thought to be produced by ____________________, a condition in which too much endolymph accumulates in the inner ear.