Which cranial nerve is involved in pupillary constriction and eye lid elevation?

The cranial nerve involved in pupillary constriction and eyelid elevation is the oculomotor nerve. It plays a crucial role in controlling most of the eye's movements along with the parasympathetic functions related to the pupil and eyelid.

The oculomotor nerve innervates several extraocular muscles responsible for eye movement and also provides parasympathetic input to the iris sphincter muscle, leading to pupillary constriction in response to light. Additionally, it controls the levator palpebrae superioris muscle, which elevates the upper eyelid.

This dual function makes the oculomotor nerve essential for maintaining proper visual function and protecting the eye by adjusting the amount of light entering the pupil. Understanding this nerve's role is critical in clinical settings, as any dysfunction can lead to symptoms such as ptosis (droopy eyelid) or dilated pupils, indicating potential neurological issues.