The human nervous system is composed of
CNS
PNS
ANS
In humans, the nervous system consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and the spinal cord while the PNS consists of nerves arising from the CNS.
The PNS is divided into a) somatic nervous system (SNS) and b) autonomic nervous system (ANS).
The somatic nervous system conveys information to skeletal (voluntary) muscles.
The autonomic nervous system is further subdivided into sympathetic and parasympathetic nervous systems. The ANS includes a pair of chains of ganglia and nerves which control the involuntary actions of many internal organs like the heart muscles, smooth muscles, glands etc.