Final answer:
Antimuscarinic agents block the action of acetylcholine on muscarinic receptors and reduce parasympathetic nervous system activity, leading to effects like pupil dilation, reduced secretions, and increased heart rate.
Step-by-step explanation:
Antimuscarinic agents, also known as anticholinergic drugs, specifically bind to muscarinic receptors, which are a type of acetylcholine (ACh) receptor found in various target tissues of the parasympathetic nervous system. There are five types of muscarinic receptors, M1 through M5, but most antimuscarinic drugs do not differentiate between these subtypes. These agents inhibit parasympathetic nerve impulses by selectively blocking the binding of ACh to its receptors, which leads to decreased activity in the parasympathetic nervous system.
The effects of antimuscarinic agents include mydriasis (dilation of the pupil), decreased secretions such as saliva and mucus, relaxation of smooth muscles (leading to decreased bowel motility and bronchodilation), as well as tachycardia due to blocking the inhibitory influence of the parasympathetic nervous system on the heart.