Cardiac cycle

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.<ref name="cardiac_cycle">

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</ref> 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

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.<ref name="diastole">

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Systole Phase

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.<ref name="systole">

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Regulation of the Cardiac Cycle

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.<ref name="sa_node">

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Clinical Significance

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.<ref name="clinical_significance">

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Related Pages

• Heart
• Diastole
• Systole
• Electrical conduction system of the heart

References

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