The central nervous system (CNS) is the part of the nervous system which consists of the brain and the spinal cord.
The central nervous system is the processing center for the nervous system consisting of complex networks of neurons. The CNS receives and integrates information from and transmits information to the peripheral nervous system (PNS).
There are two main parts of the central nervous system: the brain and the spinal cord. However, the optic nerve, which is still referred to as a cranial nerve (part of the PNS) can be considered as a part of the central nervous system as it is an extension of the brain. All the parts of the CNS are protected by three layers of connective tissue called the meninges, and are safely situated within the skull and the vertebral column.