Neuron is the functional unit of nervous system. The nervous system is basically classified into two types. They are,
1. Central nervous system (CNS)
2. Peripheral nervous system (PNS)
The peripheral nervous system includes,
(i) Somatic nervous system
• Cranial nerves
• Spinal nerves
(ii) Autonomous nervous system (ANS)
ANS is again divided into three types,
(a) Sympathetic nervous system
(b) Parasympathetic nervous system
The functional organization of the nervous system is illustrated below: