Lecture12-2009W - Two types of voltage-dependent ionic...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Action Potential b large and brief change of V m that is propagated along the memb. General properties - threshold potential - regenerative - overshoot - after hyperpolarization (= undershoot) - refractory period Four key elements for AP (1) Active transport of ions by specific protein (2) Unequal distribution of ions b electrochemical gradient (3) Ion-selective channels b (1), (2) & (3) are key elements for V rest (4) Gating (open & closing) of specific ion channels) + Absolute RP Relative RP Ionic basis of action potentials c Na + conductance (gNa) – fast c K + conductance (gK) – delayed c Equilibrium potentials (E Na , E K ) c Voltage-gated ion channels - Na channels - K channels Ohm’s law b I = V/R Then, I x = gX • emf x ( R = 1/gX) I x = gX • (V m – E x )
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Ionic currents underlying action potentials
Background image of page 2
Background image of page 3
This is the end of the preview. Sign up to access the rest of the document.

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?...
View Full Document

This note was uploaded on 03/11/2009 for the course BIOS 342 taught by Professor Tanda during the Spring '09 term at Ohio University- Athens.

Page1 / 3

Lecture12-2009W - Two types of voltage-dependent ionic...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online