The main function of the nervous system is to relay signals throughout the brain and body. Some main parts of the nervous system are the brain, spinal cord, nurons and intercostal nerves. The whole body is connected by nerves that communicate signals around the body on pain, heat, cold and other crucial factors. The spinal cord and brain is where most signals are received. For example if you hurt you finger, the pain signal relays feedback through nerves to get to the brain, telling you your hurt.