What does the 'T' wave on an ECG paper represent?

The 'T' wave on an ECG paper represents ventricular repolarization. This is the process where the ventricles, after having contracted to pump blood, return to their resting state, allowing for a new cycle of contraction to occur. During this phase, the myocardial cells in the ventricles are reestablishing their resting membrane potential, which is crucial for the heart to function effectively.

Understanding the 'T' wave is essential in interpreting an ECG, as it indicates the recovery phase of the ventricles and can provide important insights into cardiac health. Abnormalities in the shape or timing of the 'T' wave can signify issues such as electrolyte imbalances, ischemia, or other pathological conditions affecting cardiac function.

The other choices represent different phases of the cardiac cycle: atrial contraction is indicated by the 'P' wave, ventricular depolarization is observed in the 'QRS complex', and periods of rest are not specifically denoted by any single wave in the ECG tracing.