The nervous system is responsible for all behavior, thoughts, and actions in the body. It works with the endocrine system to maintain homeostasis. The nervous system has three main functions - sensory input, integration of information, and motor output responses. It is divided into the central nervous system (brain and spinal cord) and peripheral nervous system, with the peripheral system further divided into afferent and efferent divisions. Neurons are the basic structural and functional units of the nervous system and come in various types like multipolar neurons. The nervous system also contains supporting glial cells that help regulate the chemical environment for neurons.