2. I. How Skeletal Muscles Produce Movement

3. A. Origin and Insertion 1. Skeletal muscles produce movement by exerting force on tendons, which in turn pull on bone or other structures such as skin 2. Most muscles cross at least one joint a. Attached to articulating bones that form the joint

4. 3. When a muscle contracts, it draws one articulating bone toward the other a. Attachment to stationary bone is the origin 1. Usually proximal b. Attachment to moving bone is the insertion 1. Usually distal c. Belly or gaster is the fleshy part between 1. Usually closer to origin 4. Origins and insertions are named for the bones involved with

5. B.Levers and Lever Systems 1. Bones serve as levers, joints serve as fulcrums 2. The lever is acted upon by two forces a. Resistance (load) is the weight of the part being moved b. Effort is the force of the contracting muscle

6. 3. Three types of levers a. 1 st class- fulcrum is between effort and resistance b. 2 nd class- fulcrum at one end, effort at the other, and the resistance in the middle c. 3 rd class- fulcrum at one end, resistance at the other, and effort in the middle

8. 4. Leverage- the mechanical advantage gained by a lever, is largely responsible for a muscle’s strength and range of motion (ROM) a. ROM – the maximum ability to move the bones of a joint through an arc