The phrenic nerve provides motor innervation for the diaphragm allowing inspiration, as well as sensory innervation to the pericardium and mediastinal pleura.
The phrenic nerve is formed by C4 cervical spinal nerve, with contributions from C3 and C5.
- Its stimulation causes a gradual contraction of the diaphragm leading to inspiration.
- Involuntary, passive expiration is completely passive (without nervous stimulation)
- Since there are two phrenic nerves innervating the diaphragm, each nerve is responsible for its own side of the diaphragm and can work independently (although they are synchronized at the level of the brain-stem).
- Besides the motor innervation, it also provides sensory innervation to the pericardium and the mediastinal pleura
- Pain sensations conveyed by this nerve usually radiate