Final answer:
The efferent limbs of the pupillary reflex control pupil constriction through the parasympathetic system and pupil dilation through the sympathetic system, in response to variations in light exposure.
Step-by-step explanation:
The functions of the efferent limbs of the pupillary reflex include control pupil constriction and control pupil dilation. The efferent pathways are part of the body’s response mechanism in the pupillary reflex. When bright light hits the retina, a signal is sent through the afferent branch (the optic nerve) to the midbrain. The efferent response is then mediated via the oculomotor nerve, which projects to the ciliary ganglion. From there, postganglionic parasympathetic fibers release acetylcholine onto the circular fibers of the iris, causing the pupils to constrict. This process is part of the parasympathetic response. Conversely, in low light conditions, the sympathetic response is triggered, leading to pupil dilation through the release of norepinephrine onto the radial fibers of the iris.