Cardiac output is a combination of which two factors?

Cardiac output is defined as the amount of blood the heart pumps per minute, and it is calculated as the product of heart rate and stroke volume. Heart rate refers to the number of beats the heart makes in a minute, while stroke volume is the amount of blood ejected with each heartbeat.

When someone increases their physical activity, both factors can change significantly. For example, during exercise, heart rate often increases to supply more blood (and therefore oxygen) to the working muscles, while stroke volume may also increase due to improved myocardial efficiency and the heart's ability to fill and pump more effectively. Therefore, the relationship between heart rate and stroke volume is crucial for determining cardiac output under various physiological conditions.

The other options do not accurately encompass the factors that contribute to cardiac output. Blood pressure, while important for overall cardiovascular health, is a result of cardiac output and peripheral resistance rather than a direct contributor. Blood viscosity can affect circulation but is not one of the two primary factors that make up cardiac output.