Skeletal System in the Human Body Assignment Example | Topics and Well Written Essays - 500 words - 3

Skeletal System in the Human Body - Assignment Example Diarthroses joint is a small space that exists between the articulating surfaces of the two joined bones. Since no other tissues grow in this cavity, the surfaces move freely against one another. Hence, they are functionally defined as freely movable joints. Some examples include ball and socket joints and hinge joints.Synarthroses joint does not have a joint cavity. Fibrous cartilage 'or bone tissues grow between the articulating surfaces of the two joined bones and make them unable to move freely against one another. Therefore, they are functionally defined as immovable (or slightly movable) joints that do not allow free movement. Examples include the skull joints. Motor nerves supply signals from the nervous system to the muscle system. A single motor nerve fiber that supplies to a group of muscle fibers within a muscle is called a motor unit.Skeletal muscles are more rapid in contracting than cardiac and smooth muscles. Skeletal muscles are important in locomotion and movement an d consequently are of greatest interest to the ergonomist. Glucose stored in the cell or diffused into the cell from the circulatory system can be broken down anaerobically to generate ATP for muscle contractions. The all-or-none law, states that once the threshold has been reached, an action potential will continue to completion where the membrane will depolarize and then re-polarize. The all-or-none law also applies to muscle fibers. For muscles, the law states that once adequately stimulated, a muscle fiber will contract completely. Not all the muscle fibers are necessarily stimulated at the same time stated earlier, smaller motor units are recruited first and then aggressively larger motor units until the desired strength is attained. Thus, not all the muscle fibers are necessarily contracted at the same time. Fatigue results in failure of a muscle to contract in response a stimulus. The segment of the lever between the point of force exertion and the fulcrum is called the force arm and, likewise, the segment between the resistance and the fulcrum is called the resistance arm.