1. Hearing and Deafness Sarah Todd BIO 313 22 February 2006 http://www.drawingpower.org.uk/Themes04/Themes2004.htm

2. Sense of Hearing Sound physics –Sound energy transmitted through gaseous/liquid/solid medium –Vibration of medium’s molecules –Sound wave ↑ amplitude: ↑ loudness ↑ vibration: ↑ pitch 1000-4000 Hz Physiology of: –External, middle, inner ear –Nerves of the brain –Processing of acoustic information by brain parts http://www.engr.uconn.edu/~esc abi/DynamicAuditoryStimuli.html http://www.bananasontoast.org/?cat=12

3. Sound Transmission in the Ear External Ear: –External auditory canal→ tympanic membrane Middle Ear: –Tympanic membrane → middle ear: malleus → incus → stapes → oval window membrane Inner Ear: –Middle ear → inner ear: scala vestibuli → cochlear duct → organ of Corti → stereocilia → action potential along cochlear nerve Nerves of the Brain: –Cochlear nerve → brainstem (interneurons) → thalamus → auditory cortex (temporal lobe)

4. http://www.open2.net/labrats/gforce_science.htm Anatomy of the Ear Semicircular canal Temporal bone

5. http://www.acoustics.org/press/140th/noca.htm

6. Hair Cells of the Organ of Corti Inner ear/cochlea: sensory receptor cells Hair cells = mechanoreceptors Stereocilia attached to/stimulated by basilar membrane: –Cell depolarization –Cell repolarization ↑ loudness (energy): ↑ action potential frequency http://anatomy.iupui.edu/courses/histo_D502/D502f04/lecture.f04/Earf04/Ear.f04.html

7. http://ourworld.compuserve.com/homepages/dp5/evod3.htm Organ of Corti

8. http://www.iurc.montp.inserm.fr/cric/audition/english/corti/hcells/transd/transd.htm http://www.rockefeller.edu/labheads/hudspeth/graphicalSimulations.php Neural Pathways in Hearing Cochlear nerve fibers ↓ interneurons (brainstem) ↓ multineuron pathway ↓ thalamus ↓ auditory cortex (temporal lobe)

9. Loss of Hearing Exposure to high-intensity noises + Exposure to chronic noise levels ↓ Hair cells easily damaged/destroyed 20 million Americans –1/12 Americans – 8.6% population Causes: –Heredity (50%) –Accidents/Illness (50%) Hearing aids Cochlear implants http://news.bbc.co.uk/1/hi/scotland/1803505.stm

10. Bibliography  Widmaier, E.P., Raff, H., Strang, K.T. Vander’s Human Physiology: The Mechanisms of Body Function. 10 th ed. Boston: McGraw-Hill, 2005.  Lynch, E.D., Lee, M.K., Morrow, J.E., Welcsh, P.L., Leon, P.E., King, M.-C. 1997 Nonsyndromic Deafness DFNA1 Associated with Mutation of a Human Homolog of the Drosophila Gene diaphenous. Science. 278:1315-1318.  Laurent Clerc National Deaf Education Center, Gallaudet University. “Information of Deafness.” 2006..http://clerccenter.gallaudet.edu/about/faq.html#deaf3  Images/Animations from Google.com