The mammalian nervous system is organised structurally into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord and the PNS all the neurones that connect to the CNS (sensory and motor neurones).Neurones originate from either the brain or the spinal cord.The spinal cord is a column of nervous tissue that runs along the back. It is protected by the vertebrae, 33 individual bones that interlock with each other to form the spinal or vertebral column.Pairs of nerves emerge from the spinal column at intervals.