Final answer:
Long preganglionic fibers and short postganglionic fibers characterize the parasympathetic nervous system, both releasing ACh but acting on different types of receptors.
Step-by-step explanation:
In the parasympathetic nervous system, the length of preganglionic fibers are characteristically long, as they travel from the brain stem or the sacral spinal cord to reach terminal ganglia located very close to their target organs. In contrast, the postganglionic fibers in the parasympathetic division are typically short because the ganglia are located near or within the organ walls. Both types of fibers release acetylcholine (ACh) as their neurotransmitter, but they bind to different types of receptors: nicotinic receptors on ganglionic neurons for preganglionic fibers, and muscarinic receptors on the target effector tissues for postganglionic fibers.