ABSTRACT
The ANS acts through two sets of neurons: preganglionic (presynaptic) and postganglionic (postsynaptic) neurons, with the preganglionic neuronal cell bodies residing within the CNS (spinal cord and brainstem) whereas the postganglionic neurons occupying the paravertebral, prevertebral, or intramural ganglia. These sets of ganglia consist of multipolar neurons (Figure 9.3) that establish facilitatory or inhibitory synapses with the adjacent neurons, interneurons, or afferent cholinergic fibers. The multiplicity and pattern of the synaptic connectivity between the preganglionic and postganglionic neurons are aimed at intensifying autonomic response. In a slow and diffusely contacting smooth muscle, a single neuronal terminal branches markedly, innervates a large number of smooth muscle cells, maintaining a wide
distance from the innervated structure. In rapidly contracting smooth muscles, the branching of the terminals is less pronounced, and the gap between the synaptic endings and the muscle cell is very narrow.
