Physiology 3120 Lecture Notes - Lecture 3: Skeletal Muscle, Cardiac Muscle, Repolarization

• School: Western University
• Department: Physiology
• Course: Physiology 3120
• Professor: Tom Stavraky

Document Summary

Phases: rapid depolarization, rapid repolarization, plateau phase, restoration of resting potential, resting potential. 0: current from neighbouring cells depolarize cell (gap junctions) Opens fast vg na+ channels and na+ Change in conductance of sodium is brief. 1: na+ permeability decreases (fast na+ channels close) Cl- channels open and cl- flows in (briefly) Vg k+ channels open and k+ begins moving out. Both cl- and k+ produce an outward positive current (contributing to brief repolarizing phase) 2: ap opens slow (l-type) ca2+ vg channels ca2+ moves in slowly causing slow inward current. This inward ca2+ current almost balances the outward k+ current that"s still. Result is a relatively stable membrane potential plateau phase ; inward and outward currents are not exactly equal so not perfectly horizontal occurring. A little bit more k+ moving out than ca2+ moving in. Inward movement of ca2+ decreases while k+ continues to move outwards.