Which nerve innervates the sternocleidomastoid muscle?

The sternocleidomastoid muscle, which is responsible for rotating and flexing the head and neck, is innervated by the accessory nerve. This nerve, also known as cranial nerve XI, primarily provides motor function. It emerges from the medulla oblongata, traverses the jugular foramen, and innervates the sternocleidomastoid as well as the trapezius muscles, facilitating head and shoulder movements.

Understanding this aspect of anatomy is crucial for athletic trainers, as injuries or conditions affecting these muscle movements can impact an athlete's performance and rehabilitation strategies. The accessory nerve’s role in neck and shoulder movements also highlights its importance in activities like overhead sports, contact sports, and even daily functional movements, making knowledge of its function essential in the training and rehabilitation context.