Define stroke volume.

• A. The amount of blood ejected by the ventricle with each heartbeat (about 70 mL at rest)
• B. The total blood volume
• C. The amount of blood ejected per minute
• D. The volume of blood remaining in the ventricle after systole

Answer: (A)

Stroke volume is the amount of blood ejected by the ventricle with each heartbeat. It reflects how much blood is pumped out during a single contraction and is calculated as end-diastolic volume minus end-systolic volume. In a typical resting adult, about 60–80 mL are pumped with each beat, commonly approximated as ~70 mL. This value can change with preload (venous return), afterload (arterial pressure the heart must overcome), and contractility (strength of ventricular contraction). Cardiac output, the overall blood flow, equals stroke volume multiplied by heart rate. The other descriptions refer to total blood volume, the amount pumped per minute, or the volume remaining after systole, which are not stroke volume.