Final answer:
The diaphragm is innervated by the phrenic nerve, which originates from the cervical plexus and connects to the spinal cord at cervical levels 3 to 5, crucial for respiratory function.
Step-by-step explanation:
The diaphragm is innervated by the phrenic nerve. This systemic nerve stems from the cervical plexus and is responsible for the muscle contractions that enable breathing. The phrenic nerve connects to the spinal cord at cervical levels 3 to 5, making it a vital part of the respiratory system. Innervation by the parasympathetic and sympathetic nervous systems provides additional control through the dilation and constriction of the airway. The dorsal respiratory group (DRG) in the medulla oblongata also plays a key role in stimulating contraction of the diaphragm for inspiration.