Pupils typically react by doing what in response to fights, drug use, and certain eye drops?

• A. Constrict
• B. Dilate
• C. No change
• D. Unequal

Answer: (B)

Pupils change size through the autonomic nervous system. The dilation is driven by the sympathetic system acting on the iris dilator muscle, while constriction is caused by the parasympathetic system acting on the sphincter muscle. In response to fights and arousal, the body activates the sympathetic pathway, so the pupils enlarge to let in more light and improve focus. Many drugs that stimulate the sympathetic system or mimic its effects also cause this same dilation, and certain eye drops used to dilate the pupil for examinations (mydriatics) produce the same result. So, the usual reaction in these situations is pupil dilation.

Constricting would reflect parasympathetic activity and is typical with bright light or certain drugs, not the scenarios described. No change or unequal size doesn’t fit the typical response to these stimuli.