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': 'When a person stands suddenly from lying down posture, there is \nSelect and explain. \nA. Increased tone of capacitance vessels., B. Increase efferent discharge from IX cranial nerve, C. Decreased heart rate, D. All of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: (A) Increased tone of capacitance vessels. > It occurs due to noradrenergic impulses causing venoconstriction via their action on a1 and a2 - adrenergic receptors on systo veins.', 'role': 'assistant'}]