The document discusses the nervous system and its major parts. It identifies the brain, spinal cord, and neurons as the key components. The brain is made up of the cerebrum, cerebellum, and medulla oblongata. The cerebrum is the largest part and controls complex functions. The spinal cord connects the peripheral nervous system to the brain and transmits nerve impulses. Neurons are the basic unit of the nervous system and form a network to send and receive messages throughout the body.