Final answer:
Acetylcholine acts on both nicotinic and muscarinic cholinergic receptors, which are involved in various functions within the autonomic nervous system.
Step-by-step explanation:
Acetylcholine exerts its effect on cholinergic receptors, which include both the nicotinic and muscarinic receptors. These receptor types are distinguished by their different responses to specific molecules, similar to locks and keys; nicotine activates nicotinic receptors, whereas muscarine activates muscarinic receptors. However, acetylcholine, much like a master key, can activate both types of receptors. In the context of the autonomic system, all preganglionic fibers, both sympathetic and parasympathetic, release acetylcholine which then binds to nicotinic receptors on ganglionic neurons, while postganglionic parasympathetic fibers release acetylcholine that binds to muscarinic receptors.