Systole timing in cardiac cycle pressure graph

Steps:

• Identify atrial systole as contraction phase pushing blood into ventricles, marked by pressure rise in atrium before ventricular contraction.
• Locate left atrial systole start at T (onset of atrial pressure peak) and end at U (peak and decline as ventricles fill).
• Identify ventricular systole as ejection phase, marked by sharp pressure rise in ventricle after AV valves close.
• Locate right ventricular systole start at V (isovolumetric contraction onset) and end at X (pressure drop as semilunar valves close).

Why A is correct:

• Matches standard graph: left atrial systole T-U (pre-ventricular contraction); right ventricular systole V-X (ejection phase per pressure waveform).

Why the others are wrong:

• B shifts atrial systole too late (U-V overlaps ventricular filling end).
• C lacks options, incomplete.
• D starts atrial systole at V (during ventricular systole, incorrect timing).

Final answer: A