On an EKG, the QRS complex represents?

The QRS complex on an electrocardiogram (EKG) specifically represents ventricular depolarization. This is the electrical event that triggers the ventricles to contract, pumping blood to the lungs and the rest of the body. During this phase, the depolarization wave travels through the ventricles, leading to their contraction which is crucial for the effective circulation of blood.

In contrast, the other concepts mentioned pertain to different phases or events in the cardiac cycle. Atrial contraction occurs earlier in the cycle and is represented by the P wave. The entire electrical activity of the heart encompasses not only the depolarization and repolarization but also the various waves and intervals seen on an EKG, so it is broader than what the QRS complex signifies specifically. Finally, the resting state of the heart refers to periods of inactivity and is represented by the baseline or isoelectric line on the EKG, rather than any specific complex or wave. Therefore, the correct answer accurately identifies the specific function and significance of the QRS complex in the cardiac cycle.