Location and Structure of Skeletal Muscles

The muscle that moves a particular bone is usually not located on that same bone but on the bone lying just proximal to it — for example, the biceps and triceps that move the forearm are located in the upper arm, not the forearm itself. At any joint, one of the two articulating bones is stationary and the other is movable.

Based on their role in bringing about a movement, striated muscles are grouped into three functional classes (Chart 16.1):

• Agonists (prime movers) — bring about the initial movement of a part, e.g. the biceps in elbow flexion.
• Synergists — assist the prime mover in producing the movement, e.g. the brachialis assisting the biceps.
• Antagonists — bring about the action opposite to that of the prime mover, e.g. the triceps opposing the biceps. …