Final answer:
Parasympathomimetic or cholinergic agents stimulate the parasympathetic nervous system by enhancing the effects of ACh or mimicking its action at muscarinic receptors. Anticholinergic drugs lower parasympathetic activity, and adrenergic drugs enhance sympathetic activity.
Step-by-step explanation:
The agents that stimulate the parasympathetic nervous system are known as parasympathomimetic or cholinergic. These agents work by either mimicking the action of acetylcholine (ACh) or by enhancing its effects. Postganglionic parasympathetic fibers release ACh, which binds to muscarinic receptors on target cells to exert parasympathetic effects. Therefore, the drugs that enhance cholinergic effects, acting similar to ACh, are parasympathomimetic drugs. On the other hand, anticholinergic drugs block the muscarinic receptors, lowering the parasympathetic activity. Adrenergic drugs mimic the sympathetic nervous system by binding to adrenergic receptors, leading to increased sympathetic activity, whereas parasympathomimetic agents increase parasympathetic activity.
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