Attached to the body’s skeleton via flexible tendons, striated muscles are usually arranged in pairs. Each member of a pair of pulls in the direction opposite of the other one, providing precise control of the skeletal structure. For instance, the biceps are responsible for flexing the forearm and the triceps are responsible for extending the same part of the body. The contraction of striated muscle is stimulated by electrical impulses sent out by the nervous system and requires energy from ATP. Some of the bodily sources of this important substance include glycolysis, oxidative phosphorylation, and the Krebs cycle.