Question

Atropine eye drops are used to temporarily paralyze the accommodation reflex and ars a long-lasting pupil dilating agent, or mydriatic What action of atropine causes the dilation effect?

a. Decreases contraction of dilator puplilae muscle
b. Blocks contraction of sphincter pupillae muscle
c. Increases contraction of sphincter pupillau muscle
d. Enhances parasympathetic tesponses by intinsic eye muscles

Answer 1

Atropine causes pupil dilation by blocking the contraction of the sphincter pupillae muscle, inhibiting parasympathetic actions within the iris and allowing the sympathetic system to cause dilation.

Step-by-step explanation:

The action of atropine that causes the dilation effect is b. Blocks contraction of sphincter pupillae muscle. Atropine is a muscarinic antagonist that prevents acetylcholine from binding to its receptors, inhibiting the parasympathetic control that normally causes the pupil to constrict.

Atropine's effects can be contrasted with those of drugs like pilocarpine, a muscarinic agonist, which stimulates the muscarinic receptors and causes pupil constriction and ciliary muscle contraction, helping ease conditions like glaucoma. Atropine is extracted from plants of the Atropa genus, such as belladonna, which were historically used for their cosmetic effect of enlarging the eyes but can also treat anticholinergic poisoning with pilocarpine as an antidote.