Action Potentials

Action Potentials - Graded Potentials / Action Potentials...

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Graded Potentials / Action Potentials Learning Outcomes:  Describe how excitable cells produce graded potentials  Define the stages of an action potential   Describe the ionic mechanism of the action potential  Relate equilibrium potentials for Na+, K+ and Cl- to resting, graded and action potentials  Describe how action potentials propagate Know these terms! (all relative to resting potential.) Polarized Polarized:  Normal resting potential (RP), e.g., - 70 mV inside negative Depolarized Depolarized: V m  is less  negative than RP Hyperpolarized Hyperpolarized: V m  is more  negative than RP Overview: Structure of Neuron – example of an excitable cell. dendrites cell body axon axon terminal initial segment Ion Channels Excitable Membrane Channel Categories Leak Channels: o Always open, allow diffusion of K+ out of cell, responsible for resting  permeability to K+ o sodium can "sneak" through leak channels Voltage Gated Na+ Channels o Open and close in response to changes in membrane potential; three  conformations: Closed – responsive to stimulus, opened by depolarization Activated – open –allow diffusion of Na+ down concentration 
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Action Potentials - Graded Potentials / Action Potentials...

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