What organ pumps blood through the body and is associated with the QRS complex?

• A. Heart
• B. Lungs
• C. Brain
• D. Liver

Answer: (A)

The heart is the organ that pumps blood through the body, and its electrical activity shows up on an ECG as the QRS complex. That QRS complex represents ventricular depolarization, the moment when the ventricles become activated and contract to push blood out to the lungs for oxygenation and then to the rest of the body. The large, sharp spike reflects the powerful contraction of the ventricular muscles. Lungs, brain, and liver each have other roles—gas exchange, control and processing, metabolism—so they don’t perform the pumping action the heart does. The QRS complex is there specifically because the ventricles are the main pumping chambers driving blood through the systemic circulation.