ABSTRACT
Muscle defines one of several systems of the body and demonstrates unique properties that characterize its function. Skeletal muscle, comprising the muscles of the limbs, trunk, neck, and head, differs in its properties from cardiac and smooth muscle in being more dependent upon neural control. Each skeletal muscle is composed of numerous cells or fibers. Within each muscle cell or fiber are contractile proteins capable of developing tension or force at the attachment sites of the fiber. The contractile units of each cell, defined as sarcomeres, are supported by a metabolic system within the cytoplasm, which provides the substrate for these contractile proteins to interact chemically. The muscle fiber serves two functions, as it is elastic and is able to shorten and stretch to passively develop tension by its elastic components and it is also able to actively develop tension with the contractile proteins.
