The nervous system controls all the organ systems of the body and consists of the brain, spinal cord, and nerves. The brain is the control center located in the skull and made up of the cerebrum, cerebellum, and brain stem. The cerebrum controls thinking and reasoning. The cerebellum controls balance and movement. The brain stem connects to the spinal cord and controls vital functions. The spinal cord transfers messages between the brain and body through nerves. There are sensory, motor, and mixed nerves that carry messages to and from the brain for voluntary and involuntary body actions like reflexes.