Lecture 4 - Properties of action potentials The action...

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Unformatted text preview: Properties of action potentials The action potential Threshold overshoot peak of AP repolarization after hyperpolarization refractory period All-or-none (I) Refractory period 1 msec. http://www.blackwellpublishing.com/ matthews/channel.html Great moments in the study of the action potential: the pre-classical age. 1902--Bernstein suggested that RP is due to selective permeability to K + (based on Nernst eq.). He also proposed breakdown of the membrane, predicted V m = 0 mV during the AP.--He could not explain how the membrane repolarizes and how the initial ionic conditions were restored. 1902--Overton, based on work by Sidney Ringer, demonstrated that Na + ions are necessary for electrical excitability. His work was largely ignored until rediscovered by Hodgkin and Huxley in the mid 1940s. 1936--JZ Young discovered the squid giant axon.--The classical age of membrane biophysics begins!! 1937--Cole & Curtis record from squid axons, show conductance increase during AP-- support Bernsteins concept of membrane breakdown. K.S. Kacey Cole AP Membrane conductance (1900-1984) 1937--Hodgkin visits Cole to learn about squid axon. some scientists here have been getting most exciting results on the giant nerve fibres of the squid. As you know I spend my time working with single nerve fibres from crabs which are only 1/1000th of an inch thick. Well the squid has one fibre which is about 50 times larger than mine and Dr Cole has been using this and getting results which made everyone else's look silly. Their results are almost too exciting because it is a little disturbing to see the answers to experiments that you have planned to do coming out so beautifully in someone else's hands. . I don't see any prospect of being able to do this myself.(Hodgkin 1937)....
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This note was uploaded on 07/31/2009 for the course BIO 365R taught by Professor Draper during the Spring '08 term at University of Texas at Austin.

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Lecture 4 - Properties of action potentials The action...

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