The parasympathetic innervation of the heart is supplied by the right and left vagus (CN X) nerves which provide cervical cardiac nerves to the cardiac plexus. Additional cardiac branches are provided by the right and left recurrent laryngeal nerves, branches of the vagus nerve.

Unlike the sympathetic innervation, which must first synapse within chain ganglia to supply the heart with postsynaptic fibers, the parasympathetic fibers synapse at ganglia located directly on the heart and short postsynaptic fibers then supply the target organ. Parasympathetic stimulation acts to DECREASE its rate and contractility.