Cranial nerve XI.
Originates from neuronal cell bodies located in the cervical spinal cord and caudal medulla.
Cranial Nerve XI, the accessory nerve signals the contraction or relaxation of the the sternocleidomastoid.
The Cranial Nerve XI, the accessory nerve’s nucleus is in the anterior horn of the spinal cord around C1-C3, where lower motor neuron fibers mark its origin.
Most neuronal cell bodies are located in the spinal cord and ascend through the foramen magnum and exit the cranium through the jugular foramen.
It innervates the sternocleidomastoid and trapezius muscles in the neck and back.
The cranial root of the accessory nerve originates from cells located in the caudal medulla, and they are found in the nucleus ambiguus and leave the brainstem with the fibers of the vagus nerve joining the spinal root to exit the jugular foramen.