Word parts
What it means
Each cycle has two phases: systoleSIS-tuh-leeThe part of each heartbeat when the heart muscle squeezes and pumps blood out.Full entry , when the heart muscle contracts and pushes blood out, and diastoledy-AS-tuh-leeThe part of each heartbeat when the heart muscle relaxes and the chambers fill with blood.Full entry , when it relaxes and the chambers fill. The atria contract first, then the ventricles. At a heart rate of 75 beats per minute, one cycle takes about 0.8 seconds. The heart sounds S1 and S2 come from the valves closing at the start and end of ventricular systole.
Related terms
heart rate
How many times the heart beats per minute.
cardiac output
The amount of blood the heart pumps out in one minute.
systole
The part of each heartbeat when the heart muscle squeezes and pumps blood out.
diastole
The part of each heartbeat when the heart muscle relaxes and the chambers fill with blood.
depolarization
The change in electrical charge across a nerve or muscle cell's membrane that sets off a signal or a contraction.