This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Which of the following nucleus has cardio inhibitory function? 
Select and explain. 
A. Nucleus Ambiguus, B. Nucleus Tractus Solitarius, C. Rostral Ventrolateral Medulla, D. Dorsal motor nucleus of vagus
A: Nucleus Ambiguus
Answer: A: Nucleus Ambiguus 
Explanation: Ans. A. Nucleus AmbiguusThe nucleus ambiguus in its "external formation" contains cholinergic preganglionic parasympathetic neurons for the hea.These neurons are cardioinhibitory.This cardioinhibitory effect is one of the means by which quick changes in blood pressure are achieved by the central nervous system (the primary means being changes in sympathetic nervous system activity, which constricts aerioles and makes the hea pump faster and harder).