OCR GCSE Biology 2026 – 400 Free Practice Questions to Pass the Exam

The heart's natural pacemaker, known as the sinoatrial (SA) node, plays a crucial role in regulating heartbeats. This specialized group of cells is located in the right atrium of the heart and generates electrical impulses that trigger the contraction of the heart muscle. The SA node sends out signals at regular intervals, prompting the heart to beat in a coordinated manner. This ensures that the heart pumps blood efficiently throughout the body.

The pacemaker essentially determines the heart rate by controlling the timing of when the heart's chambers contract. If the pacing is disrupted, it can lead to irregular heart rhythms, which can impact overall heart function and health. The correct answer highlights this fundamental function of the SA node in maintaining the rhythmic beating of the heart, which is essential for effective circulation.