Figure 1.

Schematic representation of the origin and components of cardiac vagal pathway. Vagal activity is generated by preganglionic vagal neurons in the nucleus ambiguus (NAmb), which are tonically active. They receive phasic respiratory-related inhibitory influences from the central respiratory pattern generator and from the nucleus tractii solitary (NTS). Their axons innervate post-ganglionic motoneurones located in a ganglionic plexus on the heart itself.