This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous system, Subject name: Physiology
[{'content': 'Brain perfusion means \nSelect and explain. \nA. Mean aerial pressure - Intracranial pressure, B. Mean aerial pressure + Intracranial pressure, C. Mean aerial pressure - CVP, D. Mean aerial pressure + CVP', 'role': 'user'}, {'content': 'Answer: A \nExplanation: MAP is the average blood pressure during one cardiac cycle and can be directly measured through invasive hemodynamic monitoring or can be calculated as the systolic blood pressure, plus two times the diastolic blood pressure, divided by three. The normal range of MAP is 70 to 100 mm Hg. Ref: guyton and hall textbook of medical physiology 12 edition page number:813,814,815', 'role': 'assistant'}]