Final answer:
The phrenic nerves, originating from C3 to C5, are responsible for innervating the diaphragm, which is essential for breathing.
Step-by-step explanation:
The phrenic nerves, formed by C3-C5, supply to the diaphragm. These are systemic nerves from the cervical plexus that play a crucial role in breathing by innervating the diaphragm – the primary muscle involved in the respiratory process. Damage to the spinal cord below the mid-cervical level will not necessarily be fatal to respiration due to the location where these motor fibres enter the phrenic nerve. Additionally, the visceral fibres from the diaphragm enter the spinal cord at the same levels, ensuring the coordination of somatosensory signals from the neck and shoulder with respiratory functions.