The synapse is the gap between the nerve axon terminals heading towards the spinal cord and the next nerve cells in the signal chain. In the case of pain these nerves synapse in the back part of the spinal cord called the Dorsal horn. Nerves convert electrical energy into chemical energy and back to electrical energy. This is the way all nerve cells in the body work. This animation shows a synapse enlarged many times to illustrate the presynaptic cell, synapse and postsynaptic cell.