Skeletal muscle works in conjunction with the skeletal system to produce movement. This movement is accomplished voluntarily. In addition, skeletal muscles help stabilize joints and are important in heat production. Muscles under involuntary control include smooth and cardiac muscle. Smooth muscles control body openings and passages. Cardiac muscle is responsible for the pumping action of the heart. Medical assistants should understand the muscular system in order to give muscular injections, prepare patients for massage therapy, demonstrate ambulatory techniques, and assist in the care of sprains and strains.