Chapter 11 Notes

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Human Biology
Professor Niemeier

Chapter 11  Pinna – visible portion of ear o Sound localization  Auditory canal – entrance to inner ear  Tympanic membrane (ear drum)  Ossicles – smallest bones in body  Oval window – receives eardrum movements from ossicles  Cochlea – fluid-filled; sound – AP  Sound wave moves eardrum o Eardrum moves ossicles o Ossicles move oval window membrane o Oval window motion moves cochlea fluid o Chochlea fluid movement causes response in sensory neurons  Auditory receptors in cochlea – breain stem neurons – medial geniculate nucleus 0 auditory cortex (A1) o Malleus (hammer o Incus (anvil)  Rigid connection o Stapes (stirrup  Flexible connection  Footplate – flat bottom of stapes o Like piston at oval window o Transmits sound vibrations to fluids of cochlea in inner ear  Ossicles – for pressure amplification o Pressure = F/A  Oval window vs tympanic membrane  Attenuation reflex o To adopt ear to lound sounds o Protect from damage (50 – 100 msec delay) o Tensor tympani muscle (to malleus) and strapedius muscle (to stapes) contract and stiffen ossicles o Sound diminished  Scala vestibule – Reissner’s membrane –scala media – basilar membrane (on top of which is tectorial membrane and organ of Corti) – scala tympani  At apex – helicotrema  At base – vesticula meets oval  Tympani meets round  Perilymph – like cerebrospinal fluid o Low K+, high Na+ o In tympani and vestibule  Endolympth – like intracellular fluid o Low Na+, high K+ o In media  Stria vascularis – mediates ion concentrations  Endocochlear potential – endolymph 60mV + than perilymph  Place code – 50 Hz – 16000 Hz  Reticular lamina o Hair cells – inner, outer o Rods of Corti  Basilar membrane o Stereocilia protrude from hair cells  Bend for transduction  Hair cell – bipolar spiral ganglion cells in modiolus – auditory nerve CN VIII) – cochlear nuclei (medulla)  Stereocilia – resting potential of -70mV o Saturate at 20 nm (max o Min at 0.3 nm  TRPA channel on stereocilia tips o Each connected to each other by TIP LINKS  Resting – straight (small K+ leak)  Tilted – 1) open K+ - depolarize o 2) close K+ - hyperpolarize o Outer hair cells – cochlear amplifier  Motor proteins – change outer hair cell length  ATP not an energy source  Hair cells mo
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