A

Cardio-inhibitory vagal pre-ganglionic neurons that slow the heart are concentrated in the external formation of the nucleus ambiguus; in contrast, NTS is an afferent sensory nucleus, RVLM drives sympathetic cardio-excitatory tone, and the dorsal motor nucleus mainly supplies parasympathetic fibres to thoraco-abdominal viscera rather than to the heart itself [Agarwal, 1992, PMID 1638403; Hsieh, 1998, PMID 9686902].