The attachment to the movable bone is the insertion. B. Lever Systems and Leverage 1. Bones serve as levers and joints serve as fulcrums. C. Arrangement of Fasciculi 1. The muscle fibers are arranged in a parallel fashion within each bundle, but the arrangement of the fasciculi with respect to the tendons may take one of four characteristic patterns.
Fascicular arrangement is correlated with the power of a muscle and the range of motion.
D. Group Actions 1. Most movements also involve muscles called synergists, which serve to steady a movement, thus preventing unwanted movements and helping the prime mover function more efficiently. An example would be the extensor carpi muscles act as synergists for the flexor digitorum muscles to prevent the wrist from flexing forward when the fist is clenched. Some synergist muscles in a group also act as fixators, which stabilize the origin of the prime mover so that it can act more efficiently. Under different conditions and depending on the movement and which point is fixed, many muscles act variously as prime movers, antagonists, synergists, or fixators.