The central nervous system (CNS) is the processing center for the nervous system. It receives information from and sends information to the peripheral nervous system. The two main organs of the CNS are the brain and spinal cord.he brain processes and interprets sensory information sent from the spinal cord. Both the brain and spinal cord are protected by three layers of connective tissue called the meninges. Within the central nervous system is a system of hollow cavities called ventricles.
The edge of something is the end of it, the outer limit. You can sit on the edge of your desk, on the edge of a chair, on the edge of a cliff. As stated by someone else, sitting on the edge of your seat is used to indicate tension or anticipation. You are ready to jump up out of the seat as quickly as possible.
sit on someone or something. 1. Lit. to place oneself in a sitting position on someone or something. The enormous woman knocked the crook out and sat on him until the police came. I need to sit on this chair for a minute and catch my breath. 2. Fig. to hold someone or something back; to delay someone or something. The project cannot be finished because the city council is sitting on the final approval. Ann deserves to be promoted, but the manager is sitting on her because of a disagreement.