Final answer:
Anticholinergics such as atropine and scopolamine cause pupil dilation by blocking muscarinic receptors. Atropine, historically used for cosmetic purposes, and scopolamine, used for motion sickness, can be toxic in high doses. Pilocarpine is the antidote for their poisoning, due to its action as a muscarinic agonist.
Step-by-step explanation:
Anticholinergics such as atropine, ipratropium, and scopolamine cause pupil dilation, known as mydriasis. These substances are muscarinic antagonists that block muscarinic receptors in the iris, allowing the pupil to dilate. This dilation was historically considered attractive, enhancing the appearance of the eyes, and relates to humans' instinctive attraction to larger eyes, a trait observed in infants. Atropine derives from plants in the Atropa genus, such as belladonna or deadly nightshade, and was once used cosmetically, though it is not used for such purposes anymore due to its potential toxicity. In instances of atropine or scopolamine poisoning, pilocarpine is used as the antidote because it is a muscarinic agonist, reversing the mydriasis caused by the poisoning.
Scopolamine also serves a therapeutic purpose in treating motion sickness with a controlled transdermal patch. Its main utility in medicine, along with atropine, includes reversal of mydriasis after eye exams and management of symptoms in cases of nerve agent poisoning, due to their properties as anticholinergics. Nonetheless, it is important to acknowledge the potential dangers of high doses, which can lead to fatal suppression of parasympathetic function and autonomic regulation disruption.