The ventricles are contracting when the heart is in the systolic phase. A True B False
The correct answer and explanation is:
The correct answer is A. True.
Explanation:
The cardiac cycle consists of two main phases: systole and diastole. These phases describe the contraction and relaxation of the heart muscles, respectively, and are essential for pumping blood throughout the body.
- Systole is the phase when the heart muscles contract.
- Diastole is the phase when the heart muscles relax.
More specifically, during the systolic phase, the ventricles contract. The ventricles are the two lower chambers of the heart, and their contraction pushes blood out of the heart and into the arteries:
- The right ventricle contracts to send blood to the lungs through the pulmonary artery (pulmonary circulation).
- The left ventricle contracts to send oxygen-rich blood to the rest of the body through the aorta (systemic circulation).
This ventricular contraction raises the pressure in the ventricles, causing the atrioventricular (AV) valves (tricuspid and mitral valves) to close. This closure produces the first heart sound, often described as “lub.” At the same time, the semilunar valves (pulmonary and aortic valves) open, allowing blood to flow out of the heart.
In contrast, during diastole, the ventricles relax and fill with blood coming from the atria. The semilunar valves close (producing the second heart sound, “dub”) to prevent backflow of blood into the ventricles, while the AV valves open to allow filling.
Understanding the phases of the cardiac cycle is critical in physiology and medicine because the efficiency of the heart depends on the proper timing and function of these contractions and relaxations.
Summary:
- Ventricular contraction occurs during systole.
- This contraction pumps blood out of the heart.
- The AV valves close and semilunar valves open during systole.
- Therefore, the statement “The ventricles are contracting when the heart is in the systolic phase” is True.