Individual muscle cells, or myocytes, are surrounded by a thin connective tissue sheath known as the endomysium. This protective sheath allows smooth muscle contraction by electrically insulating each individual myocyte and propagating action potentials that result in muscle contraction.
Muscle cells have three coverings. The endomysium covers each individual muscle cell. The perimysium is a connective tissue sheath that covers small bundles of muscle cells known as fascicles. The fascicles make up larger muscle bundles that are then covered by a connective tissue sheath known as the perimysium. Connective tissue is innervated by the nervous system; therefore, each muscle covering allows for smooth contraction and relaxation by propagating action potentials throughout large muscle systems.