When a light is shone into the pupil, what should happen?

When a light is shone into the pupil, what should happen?

• A. It should become larger in size.
• B. The opposite pupil should dilate.
• C. It should become smaller in size.
• D. Both pupils should dilate together.

Answer: (C)

When a light is shone into the pupil, the expected physiological response is for the pupil to constrict, or become smaller in size. This reaction is known as the pupillary light reflex, which occurs as a protective mechanism to reduce the amount of light entering the eye and to prevent damage to the retina. The constriction helps enhance visual acuity in bright light conditions. Additionally, there is a consensual response in which both pupils constrict, even if only one pupil is stimulated. This coordinated response helps maintain even visual input to the brain. Therefore, the correct answer reflects the expected response of the pupil directly receiving light. The other options suggest reactions that would not normally occur under typical circumstances. For instance, dilation of the pupil in response to light is counterintuitive to the pupil's primary function of regulating light entry. The response of the opposite pupil would typically exhibit constriction rather than dilation when light is shone in one eye.

When a light is shone into the pupil, the expected physiological response is for the pupil to constrict, or become smaller in size. This reaction is known as the pupillary light reflex, which occurs as a protective mechanism to reduce the amount of light entering the eye and to prevent damage to the retina. The constriction helps enhance visual acuity in bright light conditions.

Additionally, there is a consensual response in which both pupils constrict, even if only one pupil is stimulated. This coordinated response helps maintain even visual input to the brain. Therefore, the correct answer reflects the expected response of the pupil directly receiving light.

The other options suggest reactions that would not normally occur under typical circumstances. For instance, dilation of the pupil in response to light is counterintuitive to the pupil's primary function of regulating light entry. The response of the opposite pupil would typically exhibit constriction rather than dilation when light is shone in one eye.