Which cranial nerve is involved in head turning and shoulder shrug?

The cranial nerve involved in head turning and shoulder shrug is the spinal accessory nerve. This nerve is responsible for innervating the sternocleidomastoid and trapezius muscles. The sternocleidomastoid muscle facilitates rotation of the head to the opposite side and flexes the neck, while the trapezius muscle is responsible for shoulder elevation and stabilization, particularly during movements like shrugging.

When assessing motor function related to head movement and shoulder elevation, the spinal accessory nerve is vital. This connection explains its critical role in allowing these specific movements. The other cranial nerves listed have different functions: the vagus nerve primarily affects autonomic functions, the hypoglossal nerve is mainly responsible for tongue movements, and the trochlear nerve innervates muscles that control eye movement. Thus, the spinal accessory nerve is uniquely suited for the tasks of head turning and shoulder shrugging.