Nervous system.

The nervous system is a complex network of nerves and cells that transmit signals between different parts of the body. It is responsible for coordinating and controlling all bodily functions, including movement, sensation, and thought. The nervous system is divided into two main parts: the central nervous system, which includes the brain and spinal cord, and the peripheral nervous system, which includes all the nerves that branch out from the central nervous system to the rest of the body. The nervous system plays a crucial role in maintaining homeostasis and responding to external stimuli.