Cardiac Output (CO) is defined as:

• A. The pressure that the blood exerts against the walls of the arteries as it passes through them.
• B. The mean arterial pressure in the arteries.
• C. Volume of blood pumped by the heart per minute.
• D. The amount of blood in the ventricles after filling

Answer: (C)

Cardiac output is the volume of blood the heart pumps each minute. This measure captures how effectively the heart supplies the body with blood over time and depends on two factors: heart rate and stroke volume (the amount of blood ejected with each beat). In practice, CO increases during activity as the heart beats faster and can also pump more blood with each beat, meeting the muscles’ higher demand for oxygen and nutrients.

The other concepts describe different things. Arterial pressure is the force blood exerts on the walls of the arteries, not the amount pumped per minute. Mean arterial pressure is an average pressure in the arteries over a cardiac cycle, a pressure metric rather than a volume metric. The amount of blood in the ventricles after filling refers to end-diastolic volume, which relates to preload, not the total blood expelled per minute. So the description “volume of blood pumped by the heart per minute” best defines cardiac output.