The spinal accessory nucleus is the motor nucleus for which nerve?

The spinal accessory nucleus is the motor nucleus for which nerve?

• A. Cranial Nerve IX
• B. Cranial Nerve XI
• C. Cranial Nerve X
• D. Cranial Nerve XII

Answer: (B)

The spinal accessory nucleus is the motor hub for the spinal component of the eleventh cranial nerve. This nerve has two roots: a spinal root that starts from neurons in the spinal cord (in the ventral horn of upper cervical segments) and a cranial root that arises from the medulla. The spinal root ascends to join the cranial root and together they form the spinal accessory nerve, which exits the skull to innervate the sternocleidomastoid and trapezius muscles. So the nucleus in question specifically provides the motor supply for the spinal accessory nerve (cranial nerve XI), enabling neck and shoulder movements.

The spinal accessory nucleus is the motor hub for the spinal component of the eleventh cranial nerve. This nerve has two roots: a spinal root that starts from neurons in the spinal cord (in the ventral horn of upper cervical segments) and a cranial root that arises from the medulla. The spinal root ascends to join the cranial root and together they form the spinal accessory nerve, which exits the skull to innervate the sternocleidomastoid and trapezius muscles. So the nucleus in question specifically provides the motor supply for the spinal accessory nerve (cranial nerve XI), enabling neck and shoulder movements.