NCLEX : Heart

Study concepts, example questions & explanations for NCLEX

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Example Questions

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Example Question #11 : Circulatory System

Which of the following causes the S1 heart sound (lub)?

Possible Answers:

The opening of the aortic and pulmonary valves

The opening of the tricuspid and mitral (AV) valves

The closing of the aortic and pulmonary valves

The closing of the tricuspid and mitral (AV) valves

Correct answer:

The closing of the tricuspid and mitral (AV) valves

Explanation:

The S1 heart sound (sometimes referred to as "lub") is caused by the sudden snapping-shut of the tricuspid and mitral valves during systole, when the heart contracts and tension on the chordae tendinae is released. No sound is produced on the opening of these or any other valves in the heart.

Example Question #11 : Circulatory System

The contraction rate is set in what area of the heart?

Possible Answers:

The sinoatrial node

The bundle of His

The Purkinje fibers

The atrioventricular node

Correct answer:

The sinoatrial node

Explanation:

The contraction rate for the heart is set by the cells of the sinoatrial node, also known as the pacemaker cells of the heart. These cells have membranes that are especially permeable to ions, and are able to depolarize on their own at a rate of 70-100 beats per minute. All the other areas listed do have their own spontaneous contractility, but their rates are slower than that of the sinoatrial node. Thus, the sinoatrial node is the pacemaker in a healthy heart.

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