Final answer:
In sinus rhythm, the QRS complexes are regular and represent the depolarization of the ventricles in the heart.
Step-by-step explanation:
The QRS complex represents the depolarization of the ventricles in the heart during a normal sinus rhythm. It is a large and distinct waveform consisting of three peaks, Q, R, and S. The QRS complex occurs after the P wave, which represents atrial depolarization. The duration of the QRS complex is typically less than 120 milliseconds in a healthy individual. In sinus rhythm, the QRS complexes should be regular and appear in a consistent pattern.