Preload vs afterload: Preload is described as blood loading up before the heart.

• A. Blood loading up before the heart
• B. Blood loading up after the heart
• C. Blood leaving the heart
• D. Blood going to the lungs

Answer: (A)

Preload is the amount of blood in the ventricle at the end of diastole, just before the heart contracts. This filling stretches the ventricular myocardium and sets the initial length of the cardiac muscle for the upcoming beat. Saying blood is loading up before the heart describes this filling phase prior to contraction, which is exactly what preload measures. The other ideas describe events after filling: blood leaving the heart happens during systolic ejection; blood loading up after the heart would imply filling after contraction, which isn’t preload; blood going to the lungs describes blood’s path after ejection into the pulmonary circulation, not the filling of the ventricle.