Final answer:
The topical, cosmetic application of atropine or scopolamine from the belladonna plant does not cause fatal poisoning because it blocks muscarinic receptors in the iris, allowing the pupil to dilate. Ingesting atropine or scopolamine can be fatal due to its effects on parasympathetic function. The berries of the belladonna plant are highly toxic and can be mistaken for other berries.
Step-by-step explanation:
The topical, cosmetic application of atropine or scopolamine from the belladonna plant does not cause fatal poisoning because the active chemicals in the plant block the muscarinic receptors in the iris, allowing the pupil to dilate and making the eyes appear larger. However, when ingested, atropine or scopolamine can suppress parasympathetic function, disrupt autonomic regulation, and lead to anticholinergic symptoms, which can be fatal. The toxicity of the berries from the belladonna plant can be mistakenly ingested, causing poisoning. The antidote to atropine or scopolamine poisoning is pilocarpine.