The main organs of the nervous system, that is the brain and the spinal cord form the central nervous system. Brain. The brain is one of the most important organs in the human body system. It is the center of all commands.It monitors all the conscious and unconscious processes of the body.he PNS is further divided into the somatic nervous system and the autonomic nervous system. The somatic nervous system contains sensory (afferent) neurons that carry information from organs/muscles to the CNS, and motor (efferent) neurons that carry information from the brain and spinal cord to muscles of the body.