01:830:331 Lecture Notes - Lecture 5: Resting Potential, Membrane Potential
24 Jul 2016
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Document Summary
~step by step events in an action potential: Something depolarizes the cell enough to reach threshold of excitation. Membrane potential jumps from -70 to +40 mv. K+ rushes out of cell, down electrostatic gradient. After action potential reaches peak (+40 mv), sodium channels become refractory. Refractory means channels are blocked, won"t open until cell goes back to resting potential (-70 mv) Repolarization because cell is now positively charged, k+ continues leaving, now down both electrostatic and diffusion gradient, and brings cell closer to resting potential. Potassium leaving causes inside of cell to become more negative, until resting potential is reached. Potassium channels start closing as cell becomes more negative. When resting potential is reached, sodium channels go from refractory back to closed. Closed is the default setting, another action potential can start it all over again. Hyperpolarization membrane potential gets so low that it goes beyond -70 mv.
