Final answer:
The P wave in an ECG represents the depolarization of the atria, triggering their contraction. It is a small wave that occurs before the QRS complex.
Step-by-step explanation:
The P wave in an electrocardiogram (ECG) represents the depolarization of the atria, which is the electrical activity that triggers the contraction of the atria. It is a small wave that occurs before the QRS complex. The atria start contracting shortly after the P wave begins.
For example, in a normal sinus rhythm, the P wave has a duration of less than 0.08 seconds (typically around 0.08 seconds or smaller). It represents the electrical activity that spreads through the atria, initiating their contraction to push blood into the ventricles.
Overall, the P wave is an important component of the ECG and reflects the electrical activity in the atria during a heartbeat.