What functions does the trochlear nerve (CN IV) control?

The trochlear nerve, also known as cranial nerve IV, is primarily responsible for innervating the superior oblique muscle of the eye. This muscle plays a crucial role in the movement of the eye, specifically in downward and lateral gaze. By controlling the superior oblique muscle, the trochlear nerve facilitates actions such as looking downwards and helps in coordinating eye movements during activities like reading or descending stairs.

Understanding this function is essential, as it highlights the specific motor role of the trochlear nerve in ocular movements, differentiating it from other cranial nerves that may be involved in different areas, such as sensory functions or innervating different muscles.