What does the oculomotor nerve (Cranial Nerve III) primarily control?

The oculomotor nerve, also known as cranial nerve III, primarily controls eye movement and pupillary constriction. This nerve innervates several extraocular muscles, which are responsible for moving the eye up, down, and medially. It also controls the levator palpebrae superioris muscle, which elevates the upper eyelid. In terms of pupillary function, the oculomotor nerve mediates the constriction of the pupil in response to light, thereby assisting in the regulation of the amount of light that enters the eye and maintaining optimal vision.

The other options provided do not accurately describe the functions supervised by the oculomotor nerve. Vision is indeed related to the function of the optic nerve (cranial nerve II), and smell is controlled by the olfactory nerve (cranial nerve I). Facial expressions are managed by the facial nerve (cranial nerve VII), while chewing movements are primarily facilitated by the trigeminal nerve (cranial nerve V). This distinction highlights the specific role the oculomotor nerve plays in ocular motility and pupillary response, making it essential for visual focus and clarity.