what is a human nervous system
The human nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS, in turn, is divided into the brain and the spinal cord, which lie in the cranial cavity of the skull and the vertebral canal, respectively.he central nervous system, which includes the spinal cord and the brain, is the most protected organ in the human body. It is protected from the external environment by three barriers: skull, meninges, and cerebral spinal fluid (CSF).