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Chapter 8: Problem 2

The first heart sound represents which portion of the cardiac cycle? a. atrial systole b. ventricular systole c. closing of the atrioventricular valves d. closing of the semilunar valves

Short Answer

Expert verified
Answer: The first heart sound (S1) in the cardiac cycle represents the closing of the atrioventricular valves (tricuspid and mitral valves) during ventricular systole (contraction) to prevent the backflow of blood into the atria.

Step by step solution

01

Understanding the Cardiac Cycle

The cardiac cycle consists of two phases: systole (heart muscle contracts to pump blood) and diastole (heart muscle relaxes to allow the chambers to fill with blood). During systole, atria contract first (atrial systole) followed by ventricles (ventricular systole). During these phases, valves open and close to ensure one-way blood flow.
02

Overview of Heart Valves and Sounds

There are four valves in the heart: 1. Atrioventricular (AV) valves: tricuspid and mitral valves, regulate blood flow between atria and ventricles. 2. Semilunar valves: pulmonary and aortic valves, regulate blood flow from ventricles to the pulmonary artery and aorta. There are two main heart sounds "lub" and "dub" (S1 and S2). These sounds are produced by the closing of these valves.
03

Identifying the First Heart Sound (S1)

The first heart sound "lub" (S1) occurs during ventricular systole (contraction) and represents the closing of the atrioventricular valves (tricuspid and mitral valves) to prevent backflow of blood into the atria.
04

Conclusion

According to the above explanation, the correct answer is (c) closing of the atrioventricular valves. This represents the first heart sound (S1) in the cardiac cycle.

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Most popular questions from this chapter

Most blood enters the ventricle during ________. a. atrial systole b. atrial diastole c. ventricular systole d. isovolumic contraction

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