Final answer:
The diaphragm's motor functions are enabled by the phrenic nerve, which originates from the C3-C5 levels of the cervical spine. This innervation pathway secures continued breathing even if lower parts of the spinal cord are damaged, as the nerve roots are located above common injury sites.
Step-by-step explanation:
The diaphragm is innervated by the phrenic nerve, which is a systemic nerve from the cervical plexus that originates from the spinal cord at cervical levels 3 to 5 (C3-C5). These motor fibers are responsible for the muscle contractions that facilitate breathing. Notably, the phrenic nerve allows for the connection of the diaphragm to the central nervous system, which is vital for the involuntary process of ventilation, as directed by the respiratory centers in the brain, such as the dorsal respiratory group (DRG) and the ventral respiratory group (VRG). Consequently, spinal cord damage below the mid-cervical level does not typically result in cessation of breathing, as the phrenic nerve bypasses this potential problem by having its roots at a higher level in the cervical spine. This unique anatomical pathway ensures functionality even when lower parts of the spinal cord are compromised.