Spinal nerve anatomy, illustration. The brain and spinal cord form the body's central nervous system (CNS), with spinal nerves branching out from the spinal cord to supply different regions of the body. This illustration shows four main regions of the spinal cord (cervical, thoracic, lumbar and sacral) and the number of spinal nerves associated with them. The spinal nerves generally ennervate adjacent areas, but sometimes can supply areas relatively far away, and trapped nerves in the neck and lower back can cause pain in the arms and legs. Humans have 31 spinal nerves. The coccygeal nerve is not shown here.