Key Events in Ventricular Systole

Steps:

• Ventricular systole is the contraction phase of the ventricles, increasing pressure to eject blood.
• Atrioventricular (AV) valves close at the start to prevent backflow into atria.
• Rising ventricular pressure opens semilunar valves, allowing blood into arteries.
• Ventricular muscle contracts during systole, not relaxes (relaxation occurs in diastole).

Why C is correct:

• Ventricular systole involves contraction, which closes AV valves (event 1) and opens semilunar valves (event 3) due to pressure changes, per cardiac cycle physiology.

Why the others are wrong:

• A includes event 2 (relaxation), which happens in diastole, not systole.
• B includes event 2 (relaxation), contradicting contraction in systole.
• D includes event 2 (relaxation) and excludes event 1 (AV closure), both errors.

Final answer: C