What phase of the action potential corresponds to the T wave on an ECG?

The T wave on an electrocardiogram (ECG) represents the phase of repolarization of the ventricles, which corresponds to Phase 3 of the cardiac action potential. During this phase, the myocardial cells are restoring their resting membrane potential after depolarization.

As the action potential progresses, the initial depolarization leads to the opening of voltage-gated sodium channels, causing a rapid influx of sodium ions and the steep phase of depolarization (Phase 0). Following this, Phase 1 involves a brief repolarization where sodium channels close and potassium channels open, but this is not represented by the T wave.

Phase 2, which is also known as the plateau phase, is characterized by the influx of calcium ions that maintain depolarization for a longer duration and is represented by the ST segment on the ECG, not the T wave.

Phase 4 represents the resting state of the cardiac cells, where ion channels are closed, and no significant electrical activity occurs on the ECG. Therefore, the correct association of the T wave with Phase 3 of the action potential is essential for understanding how electrical events in the heart correlate with the rhythm seen on the ECG.