Final answer:
Nicotinic receptors are the type of receptors on ganglionic neurons that respond to acetylcholine released from preganglionic fibers in the autonomic nervous system. These are ligand-gated ion channels that cause depolarization upon ACh binding.
Step-by-step explanation:
The type of receptor that responds to acetylcholine (ACh) released by preganglionic fibers in the autonomic nervous system is the nicotinic receptor. These receptors are ligand-gated cation channels located on all ganglionic neurons, which include both sympathetic and parasympathetic ganglia. When ACh binds to these nicotinic receptors, a channel opens allowing positive ions to flood the cell membrane, resulting in depolarization of the postsynaptic membrane. In contrast, postganglionic parasympathetic fibers release ACh that binds to muscarinic receptors, which are G protein-coupled receptors, and they have a different mechanism of action that does not exclusively cause depolarization.