These impulses and are the main respiratory drive.[4,5] Action potentials are generated by the DRG to cause inspiration and expiration on a rhythmic basis. These action potentials are transmitted from the DRG down the solitariospinal tract
to the grey matter of the phrenic nucleus in cervical cord segments 4-6. From here the path follows bilateral spinal nerves out via the cervical plexus to the phrenic nerve which arises from the third, fourth and fifth cervical spinal nerve rami.