Nervous system is main controlling system of body that regulates almost all physiological, mechanical and biochemical function of body. It is considered wired system in which information are transmitted through nerves between central nervous system (brain and spinal cord) and various peripheral organs. We know that if spinal cord or brain is injured or damaged, the life of person become difficult. Person suffering from partial paralysis also loses some of their related body functions due to inactivation of nervous system. Therefore, nervous system is most vital system of body without which life is impossible. Adjustments in body functions due to changing requirements are also accomplished by nervous system, for example increased oxygen requirement of contracting muscle during physical exercise is made out by increase in respiratory functions through nervous system. Likewise cooling of body by sweating during extreme heat exposure is also done through nervous system. Thus this system not only regulates normal body function but also helps us to adjust to varying physiological and climate condition.