Which term describes the amount of blood ejected from the heart with each contraction?

• A. Heart rate
• B. End-diastolic volume
• C. Cardiac output
• D. Stroke volume

Answer: (D)

This question tests understanding of what is measured with each heartbeat. Stroke volume is the amount of blood ejected from the ventricle with a single contraction. It’s determined by how much blood is present in the ventricle at the end of filling (end-diastolic volume) and how much remains after contraction (end-systolic volume), with the typical equation being stroke volume = EDV − ESV. It’s measured in milliliters per beat.

Heart rate, on the other hand, is how many times the heart beats per minute, not how much blood is moved per beat. End-diastolic volume describes the volume in the ventricle before contraction, not the amount ejected. Cardiac output is the total blood pumped per minute and equals stroke volume multiplied by heart rate.