08/30/2026
Myocardial Action Potential Explained - Learn the Electrical Phases of the Heart Step by Step!
In this medical education lecture, you'll learn how the myocardial action potential controls every heartbeat and how the heart's electrical system allows it to contract and relax efficiently. This lesson explains the five phases of the cardiac action potential (Phase 0 to Phase 4) in simple, easy to understand language while maintaining medical accuracy.
You'll discover how sodium (Na*), calcium (Ca'*), and potassium (K*) move across heart muscle cell membranes to generate electrical impulses that coordinate normal cardiac function. We also explain where myocardial action potentials occur, including atrial muscle cells, ventricular muscle cells, and Purkinje fibers.
This lecture also connects myocardial action potentials with ECG waveforms, helping you understand how electrical events inside the heart appear on an electrocardiogram.
In this lecture, you'll learn:
What is the myocardial action potential?
The five phases of the cardiac action potential
Phase O: Rapid depolarization
Phase 1: Early repolarization
Phase 2: Plateau phase
Phase 3: Final repolarization
Phase 4: Resting phase
Functions of sodium, calcium, and potassium ions Cardiac electrical conduction
Atrial muscle cells, ventricular muscle cells, and Purkinje fibers
ECG correlation with cardiac electrical activity
Why the plateau phase is unique to heart muscle Clinical importance of the cardiac action potential
Whether you're a medical student, nursing student, pharmacy student, paramedic, physician assistant student, or healthcare professional, this lecture provides a clear and structured explanation of one of the most important concepts in cardiovascular physiology.
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Myocardial Action Potential Explained – Learn the Electrical Phases...