Cardiac cycle

Definition

The cardiac cycle is the sequence of events that occur from one heartbeat to the next. It includes phases of contraction (systole) and relaxation (diastole) of the heart chambers.

5 Must Know Facts For Your Next Test

1. The cardiac cycle consists of two main phases: systole and diastole.
2. During systole, the ventricles contract to pump blood out of the heart.
3. During diastole, the heart muscle relaxes and allows the chambers to fill with blood.
4. The cardiac cycle is regulated by electrical impulses originating from the sinoatrial (SA) node.
5. A complete cardiac cycle in a healthy adult typically lasts about 0.8 seconds.

Review Questions

• What are the two main phases of the cardiac cycle?
• What happens during systole in the cardiac cycle?
• How long does a complete cardiac cycle typically last in a healthy adult?

Related terms

Systole: The phase of the cardiac cycle when heart muscles contract to pump blood out.

Diastole:

The phase of the cardiac cycle when heart muscles relax and chambers fill with blood.

Sinoatrial (SA) Node: A group of cells located in the right atrium that regulate the heartbeat by generating electrical impulses.