Transmission in autonomic ganglia.

The activity of airway smooth muscle, glands and vasculature is under tonic control by the autonomic nervous system. Information regarding the function and state of the airway (e.g. blood flow, temperature, oxygen levels, movement, irritants, inflammation, etc.) is relayed to the central nervous system (CNS) in the form of action potentials carried by sensory nerves. This input is integrated at many levels in the CNS and this information is ultimately transformed into coded action potentials carried by various preganglionic nerve pathways from the CNS to peripheral clusters of neurons referred to as autonomic ganglia. In the autonomic ganglia the CNS-derived action potentials cause the release of neurotransmitter(s) at a synapse between the preganglionic nerve terminal and the principal ganglion neuron. The fact that synaptic transmission exists makes the ganglion neuron the final site of integration in this complex reflex pathway. Whether this transmission of information from the CNS occurs, by activating the autonomic ganglion neuron and consequently the effector organ, depends on neurochemical, anatomical, and electrophysiological factors within the ganglion that is the subject of this review.