What is the main action of CN III - Oculomotor Nerve?

The oculomotor nerve (CN III) primarily functions to control the movement of several key muscles that are responsible for eye movements. Specifically, it innervates most of the extraocular muscles, allowing for movements such as raising the eyelid and rotating the eye. Muscles such as the medial rectus, superior rectus, inferior rectus, and inferior oblique are all controlled by this nerve, facilitating actions like looking up, down, and to the sides.

In addition, CN III is also responsible for parasympathetic functions, such as constricting the pupil and controlling lens shape for focusing. This broad role in eye muscle control is what makes the answer focused on specific eye muscles correct, as it encompasses the primary motor function of CN III in coordinating eye movements. Understanding this is crucial for recognizing the anatomy and functionality of cranial nerves, especially in clinical assessments related to ocular motility and vision.