Physiology 4710A/B Study Guide - Final Guide: Friends House, Cochlea, Nmda Receptor
9 Dec 2013
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As in vision, we can use touch to distinguish edges, feel textures, read letters and recognize objects as complex as faces. We do this with very few receptor types as in vision. There are five receptors sensitive to touch: there are also receptors that sense pain and temperature. Transforming mechanical energy into electrical activity - pacinian. Mechanical stimulus (eg. pressure) deforms the receptor"s onion like membrane. Channels open and na+ flows through membrane inside of the receptor depolarizes (voltage becomes more +) If the graded potential summed at the initial segment is above threshold, ap is generated and propagated down the axon: most touch afferents have myelinated axons in which ap hop from gap to gap, thus speeding up conduction. Stimulus magnitude is encoded in part by a frequency code: greater the pressure, the more the receptor depolarizes, when above threshold, more aps/second are generated. The relationship between number of ap/second and pressure is nonlinear.
