Final answer:
In the pupillary light reflex, the oculomotor nerve (CNIII) innervates the sphincter pupillae, which constricts the pupil to limit light entering the eye. The sensory input comes from the optic nerve and leads to a motor response that is part of the autonomic nervous system, specifically the parasympathetic system releasing acetylcholine.
So, the correct answer is B) Constrictor pupillae.
Step-by-step explanation:
The oculomotor nerve (CNIII) is responsible for innervating the constrictor pupillae muscles, also known as the sphincter pupillae, which are the muscles responsible for constricting the pupils. This action occurs during the pupillary light reflex, which is an autonomic response meant to regulate the amount of light entering the eye. When light enters the eye and hits the retina, it sends a signal via the optic nerve to the brain, which then sends a signal out through the oculomotor nerve. This stimulates the sphincter pupillae to contract, thereby constricting the pupil.
The pupillary light reflex involves the sensory input via the optic nerve, while the motor response is carried out by the parasympathetic fibers of the oculomotor nerve through the ciliary ganglion. The neurotransmitter acetylcholine is released onto the circular fibers of the iris, which leads to pupil constriction. In contrast, dilation of the pupil is regulated by the sympathetic nervous system, which utilizes the neurotransmitter norepinephrine.
So, the correct answer is B) Constrictor pupillae.