What does cardiac output (Q) depend on?

Cardiac output (Q) is a crucial physiological parameter that represents the amount of blood the heart pumps in a minute. It is determined by two primary factors: heart rate and stroke volume.

Heart rate refers to the number of times the heart beats in one minute, while stroke volume is the amount of blood ejected by the left ventricle with each heartbeat. The relationship between these two components can be expressed in the equation:

Q = Heart Rate x Stroke Volume.

This equation indicates that cardiac output increases with an increase in either heart rate or stroke volume. For example, during exercise, the body requires more oxygen and nutrients, leading to an increased heart rate and potentially increased stroke volume due to enhanced venous return and stronger contractions of the heart.

Other choices that focus solely on heart rate, stroke volume, or end-diastolic volume do not account for the complete picture of cardiac output. While each of these factors plays a role in cardiovascular physiology, it is the combination of heart rate and stroke volume that ultimately determines the total cardiac output.