Question

what are the three nervous systems in human body

Answer 1

 The Human Nervous System is divided into two parts:
1.Central Nervous System{CNS} (the brain & the spinal cord).
2.Peripheral Nervous System{PNS} (nerves associated with the CNS)

Functionally, the PNS is divided into two divisions namely,
a)Somatic nervous system(SNS)  
b)Autonomic neural system(ANS)

Further, the ANS has two divisions:
i) Sympathetic division
ii) Parasympathetic division

Answer 2

The nervous system has two major parts-
1) Central Nervous System(CNS)
2) Peripheral Nervous System(PNS)