The brain works together with the spinal cord and what to form the nervous system?

Nerves and Nervous tissue. The Nervous system is the general and broad name for the system comprised of the Brain, Spinal Cord, and Nerves, that provides sensory, motor, and psychological function. The system is also split into different groups of nervous system. CNS (the Central Nervous System) contains the brain and spinal cord, and the PNS (Peripheral Spinal Cord) is comprised of the nerves that branch out of the CNS. 

Additionally you have the Sympathetic (which controls "fight or flight"; Epinephrine production, Vasodilation and Constriction, Increased HR, BP, RR) or the Parasympathetic (controls the "Breed, Rest and Digest" which controls sexual urges, muscle relaxation, widespread vasodilation, and slowing down of bodily processes, via Acetylcholine production. 

True, using a pedometer can promote a physically active lifestyle.