The human central nervous system consists of the brain and spinal cord. These lie in the midline of the body and are associated with the skull and vertebrae respectively. Arguably still the most complex object known to man, this collection of billions of neurons is the seat of consciousness and the central controller over just about everything that makes us human.
Contrast this with the peripheral nervous system and the autonomic nervous system, which pale in significance to the level of taking orders from the central nervous system.
Parts of the central nervous system: