Nucleus Tractus Solitarius
Rostral Ventrolateral Medulla
Dorsal motor nucleus of vagus
Ans. A. Nucleus Ambiguus
The nucleus ambiguus in its “external formation” contains cholinergic preganglionic parasympathetic neurons for the heart.
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 arterioles and makes the heart pump faster and harder).