Which statement describes the effect of sympathetic stimulation on the pupil?

Which statement describes the effect of sympathetic stimulation on the pupil?

• A. The pupil constricts (miosis).
• B. It dilates the pupil (mydriasis).
• C. There is no change in pupil size.
• D. The pupil changes color.

Answer: (B)

Sympathetic activation causes the pupil to dilate by stimulating the dilator pupillae muscle in the iris. This widening, or mydriasis, helps let more light into the eye during heightened alertness or stress. The opposite action is driven by the parasympathetic system, which constricts the pupil via the sphincter pupillae, resulting in miosis. The pupil does not change color with autonomic input, and there is usually a change in size rather than no change. So dilation best describes the effect of sympathetic stimulation.

Sympathetic activation causes the pupil to dilate by stimulating the dilator pupillae muscle in the iris. This widening, or mydriasis, helps let more light into the eye during heightened alertness or stress. The opposite action is driven by the parasympathetic system, which constricts the pupil via the sphincter pupillae, resulting in miosis. The pupil does not change color with autonomic input, and there is usually a change in size rather than no change. So dilation best describes the effect of sympathetic stimulation.