Cardiac Action Potential
The RMP (Resting membrane potential) is determined by the conductance to potassium ions. because
Basic Terminologies
Depolarization
It is caused by the movement of positive ions into the cardiac cell. Or inward current that brings positive charge/ions into the cell and causes depolarization of the cell membrane.
Repolarizatoin
It is caused by the movement of positive ions out of the cardiac cell. Or inward current that brings positive charge/ions out the cell and causes
Phases of Cardiac Action Potential
Phase 0
It is caused by a sudden increase in sodium inflow. this results in depolarization of the membrane. At the peak of action potential, the membrane potential approaches the sodium equilibrium potential.
Phase 1
Phase 1 begins with initial repolarization. It is caused by an increased outflow of potassium ions out of the cell and decreased inflow of the sodium ion.
Phase 2
It is the plateau of the action potential that is caused by a transient increase in calcium conductance inside the cell. During this phase, outward and inward currents are equal and thus maintains the plateau phase.
Phase 3
It is a phase of repolarization. calcium conductance is decreased in this phase and potassium conductance increases. Therefore the high potassium conductance results in large outflow of current which results in the hyperpolarization of the membrane. because
Phase 4
Phase 4 is the resting membrane potential.
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