10/12/14&1&Lesson&22&::&BIOL&1108&::&13&October&2014&!Electrical!Signals:!From!Res3ng!Poten3al!!to!Ac3on!Poten3al!1&Unit:&Animal&Form&and&Func?on&Today ’s&Topic:&&&&&D&&Res?ng&Poten?al&to&Ac?on&Poten?al&D&Today’s&learning&objec?ves:&Be&able&to:&• describe&what&an&ac?on&poten?al&is,&including&– depolariza?on&– hyperpolariza?on&2&10/12/14&2&What&two&factors&influence&membrane&poten?al?&&What&is&the&res?ng&membrane&poten?al&of&an&axon?&&3&Hyperpolariza?on&vs.&Depolariza?on&&in&the&Axon&Membrane&poten?al&(mV)&Time&0&What&happens&to&the&membrane&poten?al&with&increased&permeability&to&K+?&Membrane&poten?al&(mV)&Time&What&happens&to&the&membrane&poten?al&with&increased&permeability&to&Na+?&0&0&0&4&1)Ion concentration (diffusion)2)Electrical force-70 mVGraded Potential10/12/14&3&How&is&an&ac?on&poten?al&generated&in&an&axon?&Let’s&find&out:&Shake&hand s&with &your&neighbor!&5&Genera?ng&an&Ac?on&Poten?al&D55&+62&1&2&3&4&5&1&6&resting potentialAll Na+ voltage gated channels openNa+ channels start to close, K+ channels begin to open10/12/14&4&Genera?ng&an&Ac?on&Poten?al&Voltage!Gated!Channel!State!Charge?!Phase!Na+!K+!Membrane!Poten3al!(mV)!Inside!the!Cell!Outside!the!Cell!1!2!3!4!5!1!7&Figure 48.11-5 OUTSIDE OF CELL INSIDE OF CELL Inactivation loop Sodium channel Potassium channel Action potential Threshold Resting potential Time Membrane potential (mV) +50 -100 -50 0 Na+ K+ Key 2 1 3 4 5 1 2 3 4 5 1 Resting state Undershoot Depolarization Rising phase of the action potential Falling phase of the action potential 8&ClosedClosedClosedClosedSome OpenAll Open-70 mV-70-55-55+45+45-70-70-90-70------++++++OpenClosedClosedClosedMost ClosedSome Open10/12/14&5&Genera?ng&an&Ac?on&Poten?al&D55&+62&A&B&C&D&E&F&At&which&phase&does&depolariza?on&first&occur?&9&Genera?on&of&an&Ac?on&Poten?al&D55&+62&An&ac?on&poten?al&is&triggered&when&the&membrane&poten?al&reaches:&A. D90&mV&B. D70&mV&C. D55&mV&D. +55&mV&10&10/12/14&6&D Does&the&strength&of&a&s?mulus&affect&the&ac?on&poten?al&size&or&frequency?&Genera?on&o f&an&Ac?on &Poten?al&11&Genera?ng&an&Ac?on&Poten?al&D55&+62&A&B&C&D&E&F&At&which&phase&is&the&refractory&period?&12&10/12/14&7&Animal&Form&and&Func?on:&Electrical&Signals&&&D&&Res?ng&Poten?al&to&Ac?on&Poten?al&D&Today’s&learning&objec?ves:&Be&able&to:&• describe&what&an&ac?on&poten?al&is,&including&– depolariza?on&– hyperpolariza?on&Think&about:&D