What is the primary motor function of the facial nerve (CN VII)?

The primary motor function of the facial nerve, also known as cranial nerve VII, is to facilitate facial expressions. This nerve innervates the muscles of facial expression, allowing an individual to make a variety of facial movements, such as smiling, frowning, and raising the eyebrows. The facial nerve is responsible for conveying the commands from the brain that lead to these expressive movements, playing a crucial role in non-verbal communication and emotional expression.

While the other options pertain to functions that involve other cranial nerves or systems, they do not directly relate to the motor functions of the facial nerve. The control of eye movements is primarily managed by cranial nerves III (oculomotor), IV (trochlear), and VI (abducens). The facilitation of digestion is mainly governed by the vagus nerve (cranial nerve X), which innervates the organs involved in the digestive process. Regulating heart rate is also a function of the vagus nerve, which influences the autonomic nervous system. Thus, the unique role of the facial nerve is specifically tied to the movements associated with facial expressions, making it the correct choice.