Nervous system is the organ system that, along with the endocrine system, correlates the adjustments and reactions of an organism to internal and environmental conditions. It is composed of the brain, spinal cord, and nerves, which act together to serve as the communicating and coordinating system of the body, carrying information to the brain and relaying instructions from the brain. The system has two main divisions: the central nervous system, composed of the brain and spinal cord; and the peripheral nervous system, which is subdivided into the voluntary and autonomic nervous systems.
