Final answer:
In the autonomic nervous system, all preganglionic neurons release acetylcholine that binds to nicotinic receptors. Postganglionic parasympathetic neurons release acetylcholine that binds to muscarinic receptors, while most postganglionic sympathetic neurons release norepinephrine that binds to adrenergic receptors, with the exception for sweat glands and blood vessels in muscles.
Step-by-step explanation:
The identity of neurotransmitters secreted by pre- and postganglionic neurons of the autonomic division follows specific rules. All preganglionic neurons, regardless of whether they belong to the sympathetic or parasympathetic system, release acetylcholine (ACh). This ACh then binds to nicotinic receptors on the ganglionic neurons, which are ligand-gated ion channels leading to depolarization.
In the case of postganglionic neurons, the neurotransmitters differ based on the division. Postganglionic parasympathetic neurons release ACh, which binds to muscarinic receptors on the target cells. These muscarinic receptors are G protein-coupled receptors. However, postganglionic sympathetic neurons generally release norepinephrine, which binds to adrenergic receptors on the target cells. The exception to this is the postganglionic sympathetic fibers that innervate sweat glands and blood vessels in skeletal muscles, which, like their parasympathetic counterparts, release ACh.