Final answer:
The sympathetic system dilates the pupil while the parasympathetic system constricts the pupil in response to light levels hitting the retina.
Step-by-step explanation:
The sympathetic and parasympathetic systems play roles in controlling the size of the pupil in response to light levels hitting the retina. The sympathetic system dilates the pupil when the retina is not receiving enough light, allowing more light to reach the retina. On the other hand, the parasympathetic system constricts the pupil when there is too much light hitting the retina, reducing the amount of light that enters the eye.