Final answer:
Muscarine and nicotine have distinct effects on the autonomic nervous system due to the specificity of cholinergic receptors, separating the actions of preganglionic and postganglionic neurons in parasympathetic pathways.
Step-by-step explanation:
The different effects of muscarine and nicotine on the preganglionic to postganglionic parasympathetic synapse, as well as the postganglionic parasympathetic neuron and its target tissue synapse, prove the specificity of cholinergic receptors and their distinct physiological roles within the autonomic nervous system. Both sympathetic and parasympathetic preganglionic fibers release acetylcholine (ACh), which acts on nicotinic receptors, leading to depolarization.
Contrarily, postganglionic parasympathetic neurons release ACh that binds to muscarinic receptors on target cells, leading to varied responses rather than mere depolarization. This elucidates the importance of receptor types in mediating the actions of neurotransmitters and pharmacological agents on the autonomic system. Nicotine mimics ACh at nicotinic receptors, while muscarine affects muscarinic receptors, demonstrating their selective action on postganglionic fibers and their associated target tissues.