Final answer:
The main forms in an ECG are the P wave, QRS complex, and T wave, representing depolarization of the atria, depolarization of the ventricles, and repolarization of the ventricles, respectively.
Step-by-step explanation:
The major wave forms in an ECG (EKG) are the P wave, QRS complex, and lastly the T wave.The P wave signifies the depolarization of the atria, which is the initial electrical change during a cardiac cycle leading to the contraction of the atria. Approximately 25 ms post the onset of the P wave, the atria begin their contraction. Conversely, the QRS complex, a visibly more prominent feature in the ECG, represents the depolarization of the ventricles.
Due to the larger muscle mass of the ventricles as compared to the atria, the electrical signal required is considerably stronger. The peak of the R wave marks the beginning of the ventricular contraction. The finale of this electrical sequence is the T wave, which indicates the repolarization of the ventricles. It's worth noting that while the atria also repolarize, this activity is not visible on the ECG because it is masked by the QRS complex.