About skeletal muscle and muscle fitness Custom Search On the pages about various bones and joints (arm bones, leg bones) it is mentioned that movements take place at the joints between bones. But how are the movements of skeletal muscle actually brought about? Now you will learn about this. Movements are brought about by muscle contractions. When a muscle contracts it becomes shorter in length but slightly increases in girth. Do the following simple exercise. Keep one upper limb by the side of the body loosely without any tension. Keep the palm of the other hand on the front of arm. Now bend the elbow fully pressing it as much as you can. You will feel a lump under your palm produced by the contraction of the muscle. The contraction is brought about by the command sent by the brain. This is a voluntary muscular contraction. When you want to move any part of the body the brain sends electrical impulses to the appropriate muscles resulting in contraction. Those muscles which are under voluntary control are called skeletal muscles. It is quite obvious that in order to move a joint the muscle has to be attached to the bones on either side of the joint. It is necessary to learn something about the structure of a skeletal muscle in order to understand how it contracts. A muscle is made of muscle fibers. Many fibers make up bundles of fibers and many suck bundles constitute a muscle. Muscles vary in size, shape and orientation of fibers depending on location, the type of movement and the strength of contraction required. Each fiber represents a muscle cell.
Muscle cells are made up of special proteins called actin and myosin. These are contractile proteins which means they can shorten in length. When we want to move any part of the body the brain sends electrical impulses to the corresponding muscles through nerves. The nerves divide into many branches and supply the muscle fibers. The place where the nerve fiber comes into contact with the muscle fiber is called neuromuscular junction. The electrical impulse causes a chemical to be released at the neuromuscular junction. This triggers a series of electro-chemical changes. Please click on the graphic to enlarge.
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Page last reviewed on 2nd January 2010
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