The nervous system coordinates voluntary and involuntary actions through the central nervous system (CNS) and peripheral nervous system (PNS). The CNS contains the brain and spinal cord. The brain, which is the most complex organ, contains structures like the cerebrum, cerebellum, and brain stem that control functions like movement, balance, vision, and basic life processes. The cerebrum contains lobes that control functions like memory, speech, and emotion. The spinal cord extends from the brain and contains regions that nerves connect to throughout the body.