What is the function of the accessory nerve?

The accessory nerve, also known as cranial nerve XI, primarily functions in the innervation of certain neck muscles and plays a key role in motor control. Specifically, it innervates the sternocleidomastoid and trapezius muscles, which are crucial for movements such as turning the head and elevating the shoulders.

By innervating these muscles, the accessory nerve enables essential functions like head rotation and shoulder elevation, contributing to activities such as swallowing, where stability and position of the head and neck are important. Therefore, the choice highlighting swallowing and neck muscle innervation accurately represents the primary role of the accessory nerve.

In contrast, the other options relate to different cranial nerves or physiological functions. Taste sensations are managed by other cranial nerves, limb movement coordination is primarily the responsibility of the motor control areas of the brain and the brachial plexus, and gastrointestinal regulation involves the vagus nerve and other components of the autonomic nervous system. Hence, the answer focusing on neck muscle innervation and swallowing is aligned with the actual function of the accessory nerve.