Preganglionic fibers

Overview
In the autonomic nervous system, fibers from the CNS to the ganglion are known as preganglionic fibers.

All preganglionic fibers, whether they are in the sympathetic division or in the parasympathetic division, are cholinergic (that is, these fibers uses acetylcholine as their neurotransmitter).

Sympathetic preganglionic fibers tend to be shorter than parasympathetic preganglionic fibers because sympathetic ganglia are often closer to the spinal cord than are the parasympathetic ganglia.