Final answer:
Cardiac output and venous return are intimately connected, as the volume of blood the heart pumps out must equal the blood returning via the venous system over time. Changes in one will affect the other to maintain a balanced circulatory system.
Step-by-step explanation:
The relationship between cardiac output and venous return is critically important in the cardiovascular system. Cardiac output, which is defined as the volume of blood pumped by the heart in one minute, is calculated by multiplying heart rate (HR) by stroke volume (SV). This relationship is expressed by the equation: CO = HR × SV. Venous return is the amount of blood that flows back to the heart via the veins, and it must equal cardiac output when averaged over time, as the circulatory system is a closed loop.
Essentially, the blood that is pumped out of the heart must eventually return. Any changes in venous return will cause a corresponding change in cardiac output, assuming the heart is functioning normally. Factors such as sympathetic stimulation, catecholamines, and the Frank-Starling mechanism can affect both cardiac output and venous return.