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Hearing and Deafness

Hearing and Deafness. Sarah Todd BIO 313 22 February 2006. http://www.drawingpower.org.uk/Themes04/Themes2004.htm. Sense of Hearing. Sound physics Sound energy transmitted through gaseous/liquid/solid medium Vibration of medium’s molecules Sound wave ↑ amplitude: ↑ loudness

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Hearing and Deafness

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  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.bananasontoast.org/?cat=12 http://www.engr.uconn.edu/~escabi/DynamicAuditoryStimuli.html

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

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

  6. 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 Hair Cells of the Organ of Corti http://anatomy.iupui.edu/courses/histo_D502/D502f04/lecture.f04/Earf04/Ear.f04.html

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

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

  9. 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 Loss of Hearing 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. 10th 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

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