Question

During the systolic phase of the cardiac cycle, the heart is ________.

a. contracting

b. relaxing

c. contracting and relaxing

d. filling with blood

Short answer

The correct answer is (a) contracting

During the systolic phase of the cardiac cycle, the heart is contracting.

Step-by-step solution

Step 1. Introduction

The cardiac cycle is defined as a sequence of alternating contraction and relaxation of the atria and ventricles in order to pump blood throughout the body. It starts at the beginning of one heartbeat and ends at the beginning of another.

Step 2. Explanation for the correct answer

(a) contracting

• Systole is the period when the heart chambers contract that causes the ejection of blood into the aorta and pulmonary trunk.
• During the systolic phase of the cardiac cycle, the heart is contracting.

Step 3. Explanation for the incorrect answer 

b. relaxing

• During the systolic phase of the cardiac cycle, the heart is contracting.
• During the diastole phase of the cardiac cycle, the heart is relaxing. Hence this option is not correct.

c. contracting and relaxing

• During the systolic phase of the cardiac cycle, the heart is only contracting. Not relaxing. Hence this option is not correct.

d. filling with blood

• During the systolic phase of the cardiac cycle, the heart is contracting. Not filling with the blood. Hence this option is not correct.