Final answer:
The parasympathetic nervous system releases acetylcholine at both ganglionic synapses and neuroeffector junctions, making option c) acetylcholine, acetylcholine the correct answer.
Step-by-step explanation:
The parasympathetic nervous system releases acetylcholine (ACh) at both ganglionic synapses and its neuroeffector junctions. The correct answer to the student's question is thus c) acetylcholine, acetylcholine.
All preganglionic fibers in the autonomic nervous system, both sympathetic and parasympathetic, release ACh that binds to nicotinic receptors on ganglionic neurons.
These receptors are ligand-gated ion channels that result in depolarization. Unlike the sympathetic nervous system, which mostly releases norepinephrine at target organs (with exceptions such as sweat glands and blood vessels associated with skeletal muscles.
Where it releases ACh), the postganglionic parasympathetic fibers continue to release ACh, which binds to muscarinic receptors on the target cells that are G protein-coupled receptors.
Contrary to what might be a common misconception, the parasympathetic neurons do not release norepinephrine on the target organ.