Final answer:
A wave of depolarization traveling towards a lead on an ECG results in a positive deflection (upward). The P wave, QRS complex, and T wave on the ECG correspond to atrial depolarization, ventricular depolarization, and ventricular repolarization respectively. Atrial repolarization occurs during the QRS complex but is not distinctly visible.
Step-by-step explanation:
A wave of depolarization traveling towards a lead on an electrocardiogram (ECG) results in a positive deflection or an upward movement on the ECG trace. This can be observed in various phases of the cardiac cycle, with each phase corresponding to a specific wave or complex on the ECG.
For example, the P wave represents atrial depolarization, which occurs when the depolarization wave spreads from the sinoatrial (SA) node throughout the atria, leading to their contraction. The QRS complex, which is much larger than the P wave, corresponds to ventricular depolarization. This is due to the larger size of the ventricles and the stronger electrical signal required for their contraction. During ventricular depolarization, atrial repolarization also occurs but is masked in the ECG trace by the dominant QRS complex. Finally, the T wave represents ventricular repolarization, indicating that the ventricles are recovering from contraction and preparing for the next cycle.