Final answer:
The cervical spinal roots C3, C4, C5 are part of the cervical plexus and form the phrenic nerve, which innervates the diaphragm, neck muscles, and contribute to the control of the arms.
Step-by-step explanation:
The cervical spinal roots C3, C4, C5 send signals to the diaphragm, neck muscles, and some muscles of the brachial plexus which contribute to the control of the arms. Specifically, these roots form the phrenic nerve, which is crucial for breathing as it innervates the diaphragm. Additionally, these roots are part of the cervical plexus, which sends motor and sensory signals to the neck and shoulders area. The gray matter in the spinal cord's anterior horn is where these motor signals originate before passing through the ventral spinal roots and plexuses to reach their respective peripheral targets.