Parasympathetic motor pathways to the trachea: recent morphologic and electrophysiologic studies.

The distinctive features of the parasympathetic motor pathway to the trachea include: preganglionic fibers, many with an inspiratory rhythm, that converge onto ganglion cells and excite them through nicotinic receptors; an elaborate plexus of nerves and ganglia that covers the posterior surface of the trachea and extends anteriorly between each cartilaginous ring; ganglion cell bodies with heterogeneous morphologic and electrical properties--some large, others small, some with an inspiratory rhythm, and others with an expiratory rhythm; the trachealis muscle, which contracts with an inspiratory rhythm and closely parallels activity in the phrenic nerve.