Stroke volume is defined as which of the following?

• A. Cardiac output
• B. Heart rate
• C. Stroke volume
• D. Blood pressure

Answer: (C)

Stroke volume is the amount of blood ejected from the heart with each heartbeat, usually measured in milliliters per beat. It’s a per-beat quantity, whereas cardiac output is the total volume pumped per minute and is calculated as stroke volume multiplied by heart rate. Heart rate alone tells you how many times the heart beats each minute, not how much blood is moved per beat. Blood pressure reflects the force of blood against artery walls, not the volume ejected per beat. For example, if the stroke volume is about 70 mL per beat and the heart rate is 72 beats per minute, cardiac output is roughly 5,000 mL per minute. Understanding this distinction helps you see why stroke volume is the right definition: it specifies the amount ejected with each contraction, not the total per minute, the rate of beating, or the pressure in the arteries.