<prompt> The duration of a ventricular myocyte action potential isApproximately twice as long as the relative refractory periodAs long in duration as the QRS complexNearly as long as the QT intervalTwice as long in skeletal muscle  <response>: The diagram depicts the relationship between the electrocardiogram ECG recorded on the surface of the body and the duration of a single ventricular myocyte action potential. The duration of the ventricular myocyte refractory period is nearly as long as the action potential, approximately 300 msec. The QRS complex of an ECG represents the electrical potential on the surface of the body produced by the wave of depolarization as it spreads through the ventricle and as each myocyte depolarizes phase 0. The T wave represents ventricular repolarization phase 3 in each myocyte. Note that the ST segment occurs during the plateau phase. 