28+-+Electrically+Excitable+Cells+II

28+-+Electrically+Excitable+Cells+II - BME 418,...

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BME 418, Quantitative Cell Biology Alan J. Hunt Lecture #28: Electrically excitable cells II. From: Ionic Channels of Excitable Membranes, Hille. An important development for study of AP’s was the “ voltage-clamp ” method pioneered by Hodgkin, Huxley and Katz in 1945. Using a feedback apparatus to hold the potential constant, the current response at different voltages could be examined in isolation.
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BME 418, Quantitative Cell Biology Alan J. Hunt The circuitry required at the time was much more complicated since op-amps were not available.
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BME 418, Quantitative Cell Biology Alan J. Hunt From: Textbook of Physiology, Patton et al. Using a voltage clamp Hodgkin and Huxley were able to study the time course of the currents that were activated at different voltages. By substituting sodium in the bathing solution with membrane-impermeant choline ion the sodium current could be blocked and a repolarizing voltage-gated potassium channel was identified. CH 3 CH 3 – N + - CH 2 – CH 2 – OH Choline ion CH 3
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BME 418, Quantitative Cell Biology Alan J. Hunt From: Ionic Channels of Excitable Membranes, Hille. The RC equivalent circuit diagram for one element of the continuous cable model of an axon is now redrawn with three different resistances for the leak current and the voltage- gated sodium and potassium currents. By varying the resistance for potassium or sodium
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This note was uploaded on 03/03/2009 for the course BIOMEDE 418 taught by Professor Hunt during the Winter '08 term at University of Michigan.

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28+-+Electrically+Excitable+Cells+II - BME 418,...

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