What causes a heart to beat
A heart beats due to the electrical signals generated by specialized cells known as the sinoatrial (SA) node, which is the heart's natural pacemaker.
Located in the right atrium of the heart, the SA node sends electrical impulses through the myocardium (heart muscle) to cause it to contract. This electrical activity passes down through the atrial muscle cells, forcing them to contract and push blood into the ventricles. The contractions are coordinated in a way that the atria contract first, followed by the ventricles, ensuring efficient blood flow through the heart.
The electrical impulses then pass to the atrioventricular (AV) node, which functions as a relay station, briefly slowing the signal down so that the ventricles have time to fill with blood. After the brief delay, the signal moves along the Bundle of His and divides into the right and left bundle branches and then into the Purkinje fibers, which distribute the electrical impulse throughout the ventricles. This causes the ventricles to contract and pump blood out to the lungs and the rest of the body.
The heart's beat is regulated by the autonomic nervous system, circulating hormones, and various physiological factors. The sympathetic nervous system can increase the heart rate, while the parasympathetic nervous system can decrease it. Hormones, such as adrenaline, can also affect the heart rate during stress or exercise. The heart is adaptive in responding to the body's changing needs for blood flow and oxygen supply.