North American Veterinary Licensing Examination (NAVLE) Practice Test

The facial nerve is the primary cranial nerve responsible for facial expression and taste. It innervates the muscles of facial expression, allowing for a wide range of movements necessary for non-verbal communication and other activities such as closing the eyes and smiling. Additionally, the facial nerve carries taste sensations from the anterior two-thirds of the tongue, playing a crucial role in the sense of taste. By activating the appropriate muscles and transmitting sensory information from the tongue, the facial nerve integrates the functions of facial movement and taste perception effectively. This makes it the key player in the areas outlined in the question regarding both expression and taste.

The other cranial nerves listed do not share this dual function. The trigeminal nerve primarily serves sensory functions for the face and motor functions for mastication. The glossopharyngeal nerve contributes to taste from the posterior one-third of the tongue and is involved in other functions like swallowing, but does not facilitate facial expression. Finally, the vagus nerve primarily affects autonomic functions and does not play a direct role in either facial expressions or taste sensation.