I’m afraid I’m not really sure what you mean. Are you asking about how the nervous system is organised?
The brain is the centre of what we call the central nervous system. This is made up of the brain and the spinal cord. Everything else connects to the peripheral nervous system.
The peripheral nervous system contains the nerves that connect to your organs and remote parts of your body like your skin, eyes, fingers and teeth. The central nervous system takes information in from the peripheral nervous system into the brain and the brain processes and enacts the response if required. The peripheral nervous system contains the automatic nervous system as well. The automatic nervous system sends signals to organs that work without us actively trying like the heart or the lungs. Our brain can send messages to the automatic nervous system to increase our heart rate and breathing if we need to in times of stress, exercise or danger.