How They Work Together
Working in unison, the joints, bones and skeletal muscles of the body comprise your musculoskeletal system. The primary function of these components working together is to create movement. Other functions include stability, posture and protection. Along with the joints, which act as fulcrums, the bones and muscles work together to create levers in the body. Depending on the location of the load in relation to the joint or fulcrum, muscles and bones create either a mechanical advantage or disadvantage when you lift an object. The closer the load to the joint and the farther away the muscle, the easier it is to lift the object. Conversely, the farther the load from the fulcrum and the closer the effort to the fulcrum, the more difficult it is to move the object.
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Where They Come Together
The point of articulation, or where the muscles and the bones connect, is known as a joint. Tendons are a form of connective tissue that is continuous with muscle fiber and actually connects muscle to bone. Skeletal muscles that produce movement are attached to two bones that articulate, or meet. When movement occurs at any given joint, only one of the articulating bones will move. The stationary bone is known as the point of origin for the skeletal muscle. The bone that moves is considered the point of insertion for the muscle.
How You Move
When a neurotransmitter or message is sent for movement to occur, your body releases energy, in the form of adenosine triphosphate. ATP causes the contraction or shortening of skeletal muscle. When the specified muscle shortens, it pulls on the corresponding bone at its insertion point. This contraction shortens the distance of the angle between the articulating bones, with the joint acting as the fulcrum. Upon receiving the signal to relax, the muscle opposing the contracted muscle will then act to extend the movable bone back to its original position.
- Principles of Anatomy and Physiology, 12th Edition; G. Tortora and B. Derrickson
- NSCA's Essentials of Personal Training; R. Earle and T. Baechle