During atrial contraction, what occurs?

During atrial contraction, what occurs?

• A. Atria are in full systole, pushing remaining blood into the ventricles.
• B. Ventricles are in systole, ejecting blood into the arteries.
• C. Atria are in diastole, refilling from the veins.
• D. AV valves remain closed.

Answer: (A)

During atrial contraction the atria are in systole, actively pushing the remaining blood into the ventricles. This is the atrial kick, which helps complete ventricular filling (preload) while the ventricles themselves are still in diastole and not yet ejecting blood. The AV valves are open to allow this transfer, and the semilunar valves remain closed because ventricular pressure is still low. The other scenarios describe later or earlier phases: ventricular systole when the ventricles eject blood, atrial diastole when the atria are relaxing, and AV valves closed when flow from atria to ventricles isn’t occurring.

During atrial contraction the atria are in systole, actively pushing the remaining blood into the ventricles. This is the atrial kick, which helps complete ventricular filling (preload) while the ventricles themselves are still in diastole and not yet ejecting blood. The AV valves are open to allow this transfer, and the semilunar valves remain closed because ventricular pressure is still low. The other scenarios describe later or earlier phases: ventricular systole when the ventricles eject blood, atrial diastole when the atria are relaxing, and AV valves closed when flow from atria to ventricles isn’t occurring.