Which of the following are intrinsic factors that control stroke volume?

Which of the following are intrinsic factors that control stroke volume?

• A. Preload
• B. Contractility
• C. Afterload
• D. All of Preload, Contractility, and Afterload

Answer: (D)

Stroke volume is determined by three main influences: preload, contractility, and afterload. Preload is how much the ventricle fills before it contracts; more filling stretches the cardiac muscle and, via the Frank‑Starling mechanism, tends to increase the force of contraction and the amount ejected. Contractility is the heart muscle’s inherent ability to contract forcefully; when contractility is stronger, more blood is expelled, raising stroke volume. Afterload is the pressure the ventricle must overcome to eject blood; as afterload increases, it becomes harder to push blood into the aorta, so stroke volume tends to fall. Because each of these factors can change the amount of blood pumped with every beat, all three contribute to controlling stroke volume. For example, a rise in venous return (increasing preload) or an increase in contractility boosts SV, while a rise in arterial pressure (increased afterload) lowers SV.

Stroke volume is determined by three main influences: preload, contractility, and afterload. Preload is how much the ventricle fills before it contracts; more filling stretches the cardiac muscle and, via the Frank‑Starling mechanism, tends to increase the force of contraction and the amount ejected. Contractility is the heart muscle’s inherent ability to contract forcefully; when contractility is stronger, more blood is expelled, raising stroke volume. Afterload is the pressure the ventricle must overcome to eject blood; as afterload increases, it becomes harder to push blood into the aorta, so stroke volume tends to fall. Because each of these factors can change the amount of blood pumped with every beat, all three contribute to controlling stroke volume. For example, a rise in venous return (increasing preload) or an increase in contractility boosts SV, while a rise in arterial pressure (increased afterload) lowers SV.