Cardiac cycle

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The cardiac cycle refers to the sequence of events that occurs when the heart beats. It consists of two main phases: the diastole phase and the systole phase.[1] During the cardiac cycle, the heart chambers contract and relax to pump blood to the lungs and the rest of the body.

File:Cardiac-Cycle-Animated.gif
Cardiac-Cycle-Animated

Diastole Phase[edit]

Main article: Diastole

During the diastole phase, the heart ventricles are relaxed and the heart fills with blood. This phase consists of three stages: early diastole, when the atria and ventricles are both relaxed; atrial systole, when the atria contract to push blood into the ventricles; and late diastole, when the atria relax again.[2]

Systole Phase[edit]

Main article: Systole

During the systole phase, the ventricles contract, pumping blood out of the heart. This phase has two stages: isovolumetric contraction, when the ventricles first begin to contract with all valves closed, and ventricular ejection, when the ventricles continue to contract, pushing blood out of the heart.[3]

Regulation of the Cardiac Cycle[edit]

The cardiac cycle is regulated by the sinoatrial node (SA node), often referred to as the heart's natural pacemaker. The SA node sends out electrical signals that travel through the heart, causing it to contract and pump blood.[4]

Clinical Significance[edit]

Understanding the cardiac cycle is crucial in the field of cardiology. Disruptions in the cardiac cycle can lead to various heart conditions, including arrhythmias, heart failure, and ischemic heart disease.[5]

Related Pages[edit]

References[edit]

  1. ↑ Cardiac Cycle(link). NCBI Bookshelf.
  2. ↑ Cardiac Cycle(link). NCBI Bookshelf.
  3. ↑ Cardiac Cycle(link). NCBI Bookshelf.
  4. ↑ How the Heart Works(link). National Heart, Lung, and Blood Institute.
  5. ↑ Cardiac Cycle(link). NCBI Bookshelf.
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