8 7 Skeletal Muscle Actions Origin and Insertion

8. 7 Skeletal Muscle Actions

Origin and Insertion We mostly think of muscles as a means for movement. So, they have to be attached to bone, right? So, for movement to be accomplished, one point of attachment should be stationary and the other movable.

Origin The immovable (or mostly immovable) end of the muscle. Fastened to bone on one side of the joint.

Insertion The movable end of a muscle. Fastened to the side of the joint that moves! When a muscle contracts, its insertion is pulled toward its origin. The head of a muscle is the part nearest its origin.

Additional notes for origin and insertion Some muscles have more than one origin or insertion. Flexion and Extension describe changes in the angle between bones that meet at a joint. Flexion – decreases the angle. Extension – increases the angle.

Interaction of Skeletal Muscles The prime mover (agonist) is the muscle that accomplishes most of the desired movement. Synergists are muscles that contract and assist the prime mover. An antagonist is a muscle that resists a prime mover’s action and cause movement in the opposite direction.

Role of the nervous system Once you learn how to make a particular movement, your nervous system takes over. To accomplish a particular motion, the antagonist must be relaxed to allow the prime mover to make the motion. Your nervous system organizes these movement so they are smooth.