The amount of blood ejected by the left ventricle in one contraction?

• A. Stroke Volume
• B. Cardiac Output
• C. End-Systolic Volume
• D. Tidal Volume

Answer: (A)

Stroke volume is the amount of blood ejected by the left ventricle with each heartbeat. During systole the ventricle contracts and pushes blood into the aorta, and the volume ejected per beat equals end-diastolic volume minus end-systolic volume. In typical resting conditions, the ventricle fills to about 120 mL (end-diastolic volume) and ejects about 50 mL (end-systolic volume), giving a stroke volume around 70 mL per beat. Cardiac output, by contrast, is the amount pumped per minute and equals stroke volume times heart rate. End-systolic volume is the amount left after contraction, not the amount ejected. Tidal volume refers to air moved during normal breathing, not blood.