NBCSN Nationally Certified School Nurse Practice Exam

The correct choice indicates that the accessory nerve is involved in the scenario described, where a student experiences shoulder tenderness and difficulty shrugging their shoulder against resistance. The accessory nerve, also known as cranial nerve XI, is primarily responsible for innervating the sternocleidomastoid and trapezius muscles. The trapezius muscle plays a critical role in shoulder elevation and stabilization, allowing the individual to shrug their shoulder.

When there is damage or impairment to the accessory nerve, the ability to perform these movements is compromised. This often presents as weakness or inability to lift or shrug the shoulder properly, which aligns with the symptoms observed in the student. Thus, the observation of shoulder tenderness and difficulty in shrugging suggests that the accessory nerve is likely affected.

In contrast, the median, ulnar, and radial nerves primarily innervate muscles of the arm and hand, and while they can affect overall arm function, they are not directly responsible for shoulder elevation. Their injuries or conditions would manifest with different symptoms, such as difficulties with gripping or pinching, rather than specific issues with shoulder shrugging. Hence, the accessory nerve's sole association with the trapezius muscle makes it the most logical answer in this context.