phystut3 - The Action Potential, revisited. AP Phase VG Na+...

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2/28/10 The Action Potential, revisited. AP Phase VG Na+ Channel (2 gates) VG K+ Channe l (1 gate) Rest Fully Closed Closed Depolariz ation Activati on gate open Closed Repolariz ation Inactiva tion gate closed Activati on gate open
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2/28/10 Define these terms in relation to the AP. Depolarization A decrease in membrane potential, from the -70 mV resting potential to a more positive potential. Repolarization The restoration of the resting membrane potential, the cell membrane potential will go from a depolarized state back to the resting potential. Hyperpolarization Occurs when the cell membrane is more “negatively” polarized than the resting membrane potential. (overshoot phase) Threshold When a sufficient depolarizing stimulus is applied to an excitable cell, the threshold is reached, causing the propagation of the actioin potential.
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2/28/10 EC-30 Example Questions 11. a) Relatively speaking how many ions (a lot or very little) move through the membrane during one action potential? Relatively few ions actually move through the membrane during a single action potential and thousands of AP’s can travel down a neuron during a very short period of time .
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2/28/10 EC-30 Example Questions 11. b) Define the “absolute” refractory period. What is its physiological significance? The absolute refractory period is the period of time in which an excitable cell can not produce and another action potential, regardless of the stimulus strength. This limits the amount of AP’s that can be fired in a given amount of time. The relative refractory period is different, if a stimulus is
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2/28/10 EC-30 Example Questions 11. c) What mechanism returns the membrane potential from +35 mV during the peak of the action potential to resting levels (- 70mV)? Is it the sodium potassium pump? Voltage gated potassium channels return the membrane potential from the peak of an action potential (+35 mV) back to resting state. They open in response to a voltage change, allowing sodium to rush out of the
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EC-30 Example Questions 11. d) Would it be possible to generate a single action potential immediately after adding a chemical that blocked the sodium/potassium pump? Why or why not? Yes is would be possible to generate a single action potential immediately after adding a chemical that blocked that Na+/K+ pump. The addition of an Na+/K+ blocker would not
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This note was uploaded on 02/27/2010 for the course PHYSIOL 2210 taught by Professor Betts during the Spring '10 term at UWO.

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phystut3 - The Action Potential, revisited. AP Phase VG Na+...

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