PHS 3341 Lecture Notes - Lecture 3: Threshold Potential, Resting Potential, Autoreceptor
20 Dec 2018
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Document Summary
Describe the phases of the action potential and the changes in ion permeability that accompany each phase. Action potentials: a brief, all or none depolarization of the membrane and conducted without decrement. Triggering event: causes the membrane to depolarize from the resting potential of -70 mv. Depolarization proceeds slowly at first, until it reaches threshold potential (-50 and -55 mv) At threshold potential, an explosive depolarization takes place. Just as rapidly, the membrane repolarizes, dropping back to resting potential. Often the forces that repolarize the membrane push the potential too far, causing after hyperpolarization - the inside of the membrane briefly becomes even more negative than normal (e. g. , -80 mv) before resting potential is restored. Overshoot: portion of the action potential during which the potential is reversed (between 0 and +30 mv) If threshold potential is not reached no action potential takes place.
