Which cranial nerve is involved in facial expressions?

The facial nerve, also known as cranial nerve VII, is directly responsible for the movement of muscles involved in facial expressions. These muscles include those that allow us to smile, frown, raise our eyebrows, and perform other expressions that convey emotion. The facial nerve emerges from the brainstem and travels through the temporal bone, branching out to innervate various facial muscles.

In addition to its motor functions, the facial nerve also carries sensory information from the anterior two-thirds of the tongue and provides parasympathetic innervation to salivary and lacrimal glands. This dual role makes it a significant cranial nerve for both expression and other functions related to the face.

In contrast, the trigeminal nerve primarily provides sensory innervation to the face and controls the muscles of mastication, the hypoglossal nerve mainly controls tongue movements, and the oculomotor nerve is involved in eye movements and pupil constriction, not facial expressions. Thus, the facial nerve is uniquely suited to the task of enabling facial expressions, making it the correct choice.