Final answer:
Venous return to the right atrium is indeed affected by venous pressure and blood volume, as these factors contribute to blood flow within the venous system and are necessary for maintaining balanced cardiovascular function.
Step-by-step explanation:
True: Venous return to the right atrium is affected by venous pressure and blood volume. This is a direct answer in 2 lines provided to aid clarity and understanding.
The explanation for this is rooted in basic cardiovascular physiology. Venous return, the process of blood flow back to the heart, is influenced by several factors including venous pressure, blood volume, compliance, viscosity of the blood, and the physical characteristics of the blood vessels such as length and diameter. When venous pressure increases, rather than decreasing flow as it would in arteries due to afterload, it instead enhances the flow in veins. This is because veins operate under lower pressure conditions compared to arteries. For effective venous return, the atrial pressure during diastole must be lower than the venous pressure, nearing zero, which normally occurs except when the atria contract.
Furthermore, factors such as the presence of one-way valves, skeletal muscle pumps, respiratory pumps, and the maintenance of vascular tone within the veins significantly contribute to venous return. The baroreceptor mechanism, specifically the atrial reflex, adjusts the heart's output to match venous return, maintaining a pivotal balance in cardiovascular function. Thus, both venous pressure and blood volume directly influence the volume of blood returning to the right atrium.