With rare exception nerve impulses from the body all must come into the spinal cord. Here the nerves synapse with spinal nerves that form tracts that run to the brain. Where pain is concerned, these tracts run through the spine to the part of the brain known as the Thalamus. The Dorsal Horn is the part of the spinal cord that receives painful nerve impulses. Here nerve axon terminals synapse with nerve cell bodies. It is here where the battle against chronic pain begins. If this part of the nervous system fails, pain can be greatly increased and difficult to bring under control. Failure can occur with NMDA receptor based wind-up, neuropathic pain and/or brain based modulating.