Postganglionic fibre

The parasympathetic nervous system. Here the postganglionic fibres are always short. The preganglionic fibres are long and pus almost up to the muscle or gland to be innervated. The preganglionic fibres arise from the brain stem (cranial nerves VII, IX and X), from the tectal region (cranial nerve III which supplies the eye, p. 38), and from the sacral region. 

Similar considerations would apply at the synapse between the preganglionic fibre and the nerve cell of the postganglionic fibre of the sympathetic and parasympathetic systems and curare is the blocking agent (fig. 7 A). 

Evidence that acetylcholine is a chemical mediator of synaptic transmission elsewhere in the central nervous system is circumstantial but convincing. Acetylcholine is the transmitter substance from motor nerves, preganglionic autonomic fibres and the postganglionic fibres of the parasympathetic system to their respective effector cells. In all these fibres, the activity of choline acetyltransferase (choline acetylase), the enzyme responsible for the synthesis of acetylcholine, is high. Conversely, its activity is negligibly low in sensory nerve fibres and transmission from these fibres is demonstrably non-cholinergic in nature . It is reasonable, therefore, to... 

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