Lecture 3 - Action Potentials

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Cell and Systems Biology
Melanie Woodin

CSB332H1S L3 Jan 16 2012Action PotentialsReadings subheadings of figures used in lecture notes in info discussed in lecture quick readover of unimportant stuffstHalf a lecture before 1 quiz to ask qsA Once get act pot depolarizing quickly up to Na eqm potquickly to K eqm pot repolarizingback to rest Timing of conductances is dif every ion channel has kinetics bhvr how opensclosesVoltagegated Na channels have faster kineticsopen faster all open w high conductance as voltagegated K channels finally openB Both channels opened by depolarization current by Nafeedback loopreaches Na eqm pot peak no more driving forcestopped by Na inactivation gate unable to be opened permeability gone no matter how much depolarization given to neuronNa conductance decreasesPeak would gradually return to Vm by NaK ATPases if only Na working but voltagegated K channels openK peaks laterDepolarize membraneincrease K conductanceoutward Krepolarization feedback loopQ often put on testsexamsMembrane pots changed by underlying ionic urrents of KNaA current recorded mixed KNaB current separateddont worry about capacitative current when instantaneously inject huge amt of current immediately charge up membrane like capacitor has nothing to do w act potEarlyinward Na current deflection by voltage clamp from flowing inLate outward K current after Na current peaksGet act pots due to these currentsVoltage clamp opposes act potrecording what current is injected by voltage clamp to oppose naturallyoccuring currentstop act pot so actually seeing opposite of what happens
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