Which cranial nerve is responsible for motor functions of facial muscles?

The facial nerve, which is the correct answer, is primarily responsible for the motor functions of the facial muscles. This cranial nerve allows for the movements of expressions such as smiling, frowning, and other facial dynamics. It innervates the muscles that control these expressions, enabling an individual to convey emotional states through facial movements.

In addition to its motor functions, the facial nerve also has sensory components, including taste sensations from the anterior two-thirds of the tongue and function in tear and saliva production, but its role in motor control of facial muscles is particularly significant in understanding its main function.

Other cranial nerves listed have distinct responsibilities that do not include direct motor control of facial expressions. For example, the trigeminal nerve is mainly involved in sensation from the face and motor functions of the chewing muscles. The abducens nerve controls lateral eye movement, and the oculomotor nerve is responsible for most eye movements and the constriction of the pupil. Thus, the facial nerve is uniquely suited to fulfill the requirement for motor functions of the facial muscles.