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Unformatted text preview: Two types of voltage-dependent ionic currents (1) Inward Na current (2) Outward K current (3) Currents underlying AP b sum of I Na + I K History: AP in the Squid giant axon b J. Young (1936), b A. Hodgkin & A. Huxley (1939) NaCl b CholineCl The Voltage-clamping Method- measuring ionic currents generated by a population of ion channels c [Na + ]out > [Na + ]in by a factor of 10. (thus E Na = +55mV & huge emf ) c Entry of positively charged Na + into the cell could produce the depolarization of memb. potential (V m ). c Peak potential (overshoot) of AP, close to calculated E Na . c Size of AP changes as function of extracellular [Na + ]. How do we know Na + is the major ionic species responsible for the AP?...
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- Spring '09
- AP, Ion channel, Ionic Currents