heartbeats

A heartbeat is the rhythmic contraction and relaxation of the heart that creates the pulse felt at arteries. Each beat results from electrical impulses that coordinate the timing of atrial and ventricular contractions. The electrical impulse typically begins in the sinoatrial node, the natural pacemaker, and travels through the atrioventricular node and other conducting pathways to trigger the cardiac cycle, which includes diastole (relaxation) and systole (contraction).

In adults at rest, the normal resting heart rate ranges roughly from 60 to 100 beats per minute. Athletes or individuals with high cardiovascular fitness often have lower resting rates. Heart rate varies with age, fitness, body position, temperature, mental state, hormones, and medications. The autonomic nervous system mediates most rapid changes: sympathetic stimulation increases rate and force of contraction, while parasympathetic activity via the vagus nerve reduces heart rate.

Measurement can be done by feeling the pulse or listening with a stethoscope; more precise assessment uses an electrocardiogram, which records the heart's electrical activity and can identify rhythm and conduction problems. The pulse and the ECG reflect different aspects of the heartbeat: the pulse is the mechanical consequence of the cardiac cycle, while the ECG tracks electrical events such as P waves, QRS complexes, and T waves.

Abnormal heart rhythms include tachycardia (too fast), bradycardia (too slow), and arrhythmias (irregular rhythms). Some variations are normal under exertion, fever, or stress, but persistent tachycardia or bradycardia may require medical evaluation. Treatments may involve lifestyle changes, medications, or devices such as pacemakers.

The heartbeat supports cardiac output, the volume of blood the heart pumps per minute, calculated as heart rate times stroke volume. Cardiac rate and rhythm are tightly regulated to meet tissue demands, and disturbances can impair tissue perfusion.