Which nerve is responsible for eye movement and has the most functions associated with it?

The oculomotor nerve is primarily responsible for eye movement and plays a crucial role in controlling several actions of the eye. It innervates the majority of the extraocular muscles, allowing for various movements such as upward, downward, and medial eye movement. Specifically, it controls the superior rectus, inferior rectus, medial rectus, and inferior oblique muscles.

In addition to its role in eye movement, the oculomotor nerve also has significant autonomic functions. It is responsible for the parasympathetic control of pupil constriction through the sphincter pupillae muscle and accommodation of the lens for near vision. This combination of muscle control and autonomic functions makes the oculomotor nerve the most versatile and functionally complex of the cranial nerves associated with eye movement.

In contrast to the oculomotor nerve, the trochlear and abducens nerves primarily control specific movements of a single muscle each, while the facial nerve is mainly involved in facial expression and does not have a direct role in eye movement. Thus, the oculomotor nerve stands out not only for its extensive control over eye movements but also for its involvement in essential parasympathetic functions.