Final answer:
The cardiac cycle involves systole, the contraction phase, and diastole, the relaxation phase, both essential for the efficient pumping of blood. Option 1 is correct..
Step-by-step explanation:
The cardiac cycle consists of alternate periods of emptying and filling, known as systole and diastole. The contraction phase when the heart pumps blood into circulation is called systole, whereas diastole is the relaxation phase when the heart chambers fill with blood. Both systole and diastole occur in the atria and ventricles and are crucial for the efficient pumping of blood to the body. An example of this is during diastole, the atria contract to pump blood into the ventricles, which are relaxed at this time. Conversely, during systole, the ventricles contract to pump blood out of the heart while the atria relax and collect blood.
The cardiac cycle consists of alternate periods of emptying and filling. These periods are called systole (contraction) and diastole (relaxation). During systole, the heart contracts and pumps blood into circulation, while during diastole, the heart relaxes and chambers fill with blood. Both the atria and ventricles undergo systole and diastole, and it is essential for these components to be regulated and coordinated for efficient blood flow.