Which cranial nerve is responsible for motor control of facial expressions?

The facial nerve, also known as cranial nerve VII, is the cranial nerve primarily responsible for the motor control of facial expressions. This nerve innervates the muscles that form the face, allowing for movements such as smiling, frowning, and other expressions that are crucial for non-verbal communication.

In addition to motor functions, the facial nerve also carries taste sensations from the anterior two-thirds of the tongue and has a role in the secretion of saliva and tears. The control of facial muscles is a key aspect of its function, making it essential for both the appearance and expressions of the face.

While other nerves mentioned in the question have distinct and important roles, they do not primarily govern facial expression. For instance, the vagus nerve is involved in autonomic functions such as heart rate and digestive tract efficiency, the trigeminal nerve is primarily responsible for sensation in the face and motor functions such as biting and chewing, and the oculomotor nerve controls most of the eye's movements and pupil constriction, without any role in facial expression. Thus, the facial nerve's specific motor function links it directly to facial expressions.