BioMedical Admissions Test (BMAT) Practice Test

The heartbeat is initiated by the Sino-Atrial Node (SAN), often referred to as the heart's natural pacemaker. This small mass of specialized cardiac muscle cells is situated in the right atrium of the heart. The SAN generates electrical impulses that spread through the walls of the atria, causing them to contract and push blood into the ventricles. This electrical activity can be detected on an electrocardiogram (ECG) as the P wave, representing atrial depolarization. The SAN's ability to produce electrical currents autonomously is crucial for maintaining a consistent heart rhythm. This self-initiating function is critical because it allows the heart to respond to the body's demands by increasing the heart rate during exercise or stress, or slowing it down during rest. In contrast, while the Atrio-Ventricular Node (AVN) plays an essential role in the conduction system of the heart by receiving impulses from the SAN and transmitting them to the ventricles, it does not initiate the heartbeat. Cardiac muscle cells are responsible for the contractile function of the heart but do not produce the electric current that starts the heartbeat. Lastly, coronary arteries are responsible for supplying blood to the heart tissue itself and do not participate in the initiation of the heartbeat