Final answer:
The parasympathetic division uses acetylcholine (ACh) as a neurotransmitter in the ganglionic neurons, releasing it onto nicotinic receptors and further onto muscarinic receptors in the target cells.
Step-by-step explanation:
The parasympathetic division exclusively uses acetylcholine (ACh) as a neurotransmitter in the ganglionic neurons. In the autonomic system, both sympathetic and parasympathetic divisions release ACh from preganglionic fibers onto ganglionic neurons with nicotinic receptors. These receptors are ligand-gated ion channels that cause depolarization when ACh binds to them. Furthermore, postganglionic parasympathetic fibers continue to release ACh, but at this point, they bind to muscarinic receptors, which are G protein-coupled receptors on the target cells, inducing rest-and-digest responses.