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Floatsinlymphaticfluid diffrequenciesmaxamplitude

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Unformatted text preview: ips of the outer hair cells Generates graded potentials in inner hair cells, which act as auditory receptor cells Listen Closely!!! Listen Closely!!! Brief Summary of Events Basilar Membrane Basilar Membrane Spiral­shaped organ in cochlea mechanically separates frequency components of sound. Floats in lymphatic fluid Dif frequencies max amplitude at dif locations on BM. High freq max response at base, closest to oval window. Low frequencies max response at apex (tip) Tonotopic organization Thinner/narrower at base of cochlea than at tip (apex) High frequencies vibrate at base­ low frequencies at the apex. Properties of the BM set up gradient, not properties of hair cells Basilar membrane Basilar membrane Hair Cells Hair Cells Transduce sound waves into neural activity 3500 inner hair cells (auditory receptors) Deflection of cilia opens mechanically gated ion channels (allow primarily K+ and Ca+2) to enter cell. Hair cell does not fire an axn potential: ions depolarize cell, opening v­gated ca+2 channels; which trigger the release of NT (Glu) at end of cell. Glu bind to receptors and thus trigger action potentials in the auditory nerve 12,000 outer hair cells­ sharpen the resolving power of the cochlea by contracting or relaxing, and changing stiffness of tectorial membrane Inner hair cells synapse w/cells that form the auditory ne...
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