This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
A pilot in Sukhoi aircraft is experiencing negative G Which of the following physiological events will manifest in such situation? 
Select and explain. 
A. The hydrostatic pressure in veins of lower limb increases, B. The cardiac output decreases, C. Black out occurs, D. The cerebral aerial pressure rises
D: The cerebral aerial pressure rises
Answer: D: The cerebral aerial pressure rises 
Explanation: during acceleration downward, force acting toward the head (negative g) increases aerial pressure at head level. But intracranial pressure also rises, so that the vessels are suppoed and do not rupture. The cerebral vessels are protected during the straining associated with defecation or delivery in the same way. If the body is accelerated upward (positive g), blood moves toward the feet and aerial pressure at the level of the head decreases Ref: Ganong's Review of Medical Physiology Twenty-Third Edition Page No:575