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Welcome back, friend!

Last month we talked about the movement of blood through the heart. If you missed that post, you can find it here.

So now, let’s add another layer: the hearts pattern of contraction.

The Contraction Sequence of the Heart

The pumping action of the heart is called contraction. This is what moves the blood forward in the system and gives you that nice beating sound (well…hopefully!)

The stages of heart contraction and relaxation can be divided up into 4 parts: ventricular diastole, atrial systole, atrial diastole and ventricular systole.

Systole is when the chamber of the heart is contracting, and diastole is when it is relaxing.

1. Ventricular Diastole
As the blood moves through the superior vena cava, inferior vena cava and pulmonary veins, it passively flows into the atria. There is no atrial contraction at this point. Think of it as the residual drops you get after you turn the hose off.

At this point, the tricuspid and mitral valves are open, allowing the blood to passively flow from the atria into the ventricles. This stage is called ventricular diastole because the ventricles are relaxed.

2. Atrial Systole
The atria contract and blood actively moves from the atria, through the tricuspid and mitral valves, into the ventricles.

3. Atrial Diastole
After the atria contract, they immediately relax, allowing the blood from the inferior and superior vena cava to again fill the right atria and the blood from the pulmonary veins to fill the left atria.

4. Ventricular Systole
The ventricles contract forcefully, which causes the pressure to increase in the ventricles. This pressure increase causes both the tricuspid and mitral valves to close and the aortic and pulmonic valves to open.

This contraction forces the blood through the pulmonic and aortic valves, sending it to the lungs and body. Once the pressure is greater in the aorta and pulmonary arteries than it is in the ventricles, the pulmonary and aortic valves close.

Heart Sounds

Most people think that the “LUB-DUB” sound of the heart is created by the contraction of the atria and the ventricles. This is actually not the case.

The first sound (LUB) is created by the tricuspid and mitral valves slamming shut as the ventricles contract.

The second sound (DUB) is created by the pulmonic and aortic valves slamming shut at the end of ventricular systole.

There can be many variations of heart sounds due to the valves not closing properly or other heart abnormalities. This can lead to heart sounds other than the LUB-DUB sound. Check out this post to hear some of those abnormalities.

Congrats! You’ve completed your cardiac foundation for nursing school.

After you are able to conceptualize the flow of blood along with the contractions and relaxations of the heart, it will be easier for you to learn the possible abnormalities that can occur in the heart.

Be sure to check out this super awesome post about left-sided heart failure. It will really help you as you head toward your cardiac exams and take care of patients with heart problems.

Comment below and tell me one cardiac topic that you find to be the most difficult to learn about.