This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Circulation: Cardiac Output, Venous Return, Subject name: Physiology
A standing person lies down. Which of the following occurs? 
Select and explain. 
A. Increase in cerebral blood flow, B. Immediately increase in venous return to heart, C. Decreased blood flow to the apex of lung, D. Increase in heart rate
B: Immediately increase in venous return to heart
Answer: B: Immediately increase in venous return to heart 
Explanation: Ans. b. Immediately increase in venous return to heart (Ref: Ganong23/e p515)Factors Affecting End Diastolic VolumeFactors Decreasing EDVFactors Increasing EDV* Increased intra-pericardial pressureQ (as a result of infection of pressure from a tumor):- Limits the extent to which ventricle can fill* Decrease in ventricular complianceQ:- Increase in ventricular stiffness produced by Ml, infiltrative disease.* Standing decreases venous returnQ* Increased total blood volume increases venous returnQ:- Constriction of vein reduces the size of venous reservoir, decreasing venous pooling and thus increasing venous return* Increased negative intrathoracic pressureQ:- Increases the pressure gradient along which blood flows to the heart* Muscle activityQ: Increases venous return as a result of pumping action