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Cardiac Cycle

Cardiac Cycle

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Description:

This lesson will explain the steps that occur when your heart muscle contracts. It will investigate the cardiac cycle and the cardiac conduction system.

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Tutorial

What's Covered

This lesson will be an overview of the processes that occur in the cardiac cycle. We will look at:

  1. Contraction and Relaxation
  2. The Function of Valves

1.Contraction and Relaxation

The cardiac cycle is a sequence of events that occurs when the chambers of our heart contract and relax. We have four chambers in our heart; the right atrium, left atrium, right ventricle, and left ventricle. When these chambers contract and relax, it acts to pump blood throughout the body. This contraction and relaxation occur at the same time on each side of the heart.

Example when the right atrium relaxes, the left atrium relaxes. When the right atrium contracts, the left atrium contracts.

Term to Know

    • Cardiac Cycle
    • All of the events that occur during one heartbeat that drive blood flow into and out of the heart; a series of well-timed pressure and volume changes within the chambers of the heart that drive blood flow throughout its chambers.

The two phases of the cardiac cycle are the:

  • Contraction phase also called systole.
  • Relaxation phase also called diastole.

Terms to Know

    • Systole
    • A term used to describe an increase in pressure and work; measured in millimeters of mercury (mmHg).
    • Diastole
    • A term used to describe a decrease in pressure and work; measured in millimeters of mercury (mmHg).

2.The Function of Valves

When our atria contract, they push blood into the ventricles. The atrioventricular valve (or AV valves) separate the atria from the ventricles, and prevent blood from flowing back into the atria once it enters the ventricle. From there, the ventricles are going to contract, and, depending on which side of the heart it is, are going to pump blood into the pulmonary artery or the aorta. The left ventricle is going to pump blood up through the aortic valves into the aorta, and the right ventricle will send blood through the pulmonary valve into the pulmonary artery. These valves will close once blood has passed through to prevent blood from flowing back. Then the ventricles will relax, and then the atria will begin to fill again for another cycle.

If you listen to your heart, you can hear this process happening. The heart makes this lub-dub sound, and this sound that your heart makes because of the closing of the heart's valves. The first “lub” sound is made by your AV valves closing simultaneously. And the "dub" sound is caused by the closing of the aortic and pulmonary valves simultaneously.

Summary

The cardiac cycle includes the all the events caused by one heartbeat. The contraction and relaxation of the atria and ventricles cause the heart to pump. Valves serve an important function in this process. They allow blood to move forward from one area to another without back flow. The sound your heart makes while beating is the sound of the valves closing.

Keep the learning, and have a great day!

Source: SOURCE: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND

TERMS TO KNOW
  • Cardiac Cycle

    All of the events that occur during one heart beat that drive blood flow into and out of the heart; a series of well-timed pressure and volume changes within the chambers of the heart that drive blood flow throughout its chambers.

  • Systole

    A term used to describe an increase in pressure and work; measured in millimeters of mercury (mmHg).

  • Diastole

    A term used to describe a decrease in pressure and work; measured in millimeters of mercury (mmHg).