The resistance the heart must overcome to eject blood during systole is called?

• A. Afterload
• B. Preload
• C. Stroke volume
• D. Atrial pressure

Answer: (A)

Afterload is the resistance the heart must overcome to eject blood during systole. It represents the arterial pressure and systemic or pulmonary vascular resistance that the ventricle must exceed to open the semilunar valves and push blood into the aorta or pulmonary artery. When afterload increases, the ventricle must generate higher pressure to eject blood, which can lower stroke volume if contractility can’t compensate. Preload is about filling pressure and volume before contraction, not the resistance to ejection; stroke volume is the amount ejected, and atrial pressure refers to pressures in the atria, not the resistance the ventricle faces.