Lab.-Act-15-Organization-of-the-Muscular-System (3).pdf

 The muscular system and muscular tissue of your body contribute to homeostasis by stabilizing body position, producing movements, regulating organ volume, moving substances within the body, and producing heat. Three types of muscles: skeletal muscle, cardiac muscle & smooth mu...

 The muscular system and muscular tissue of your body contribute to homeostasis by stabilizing body position, producing movements, regulating organ volume, moving substances within the body, and producing heat. Three types of muscles: skeletal muscle, cardiac muscle & smooth muscle Skeletal muscles are usually attached to the skeletal system via tendons to maintain posture & control movement  Epimysium a connective tissue sheath that surrounds a single muscle Perimysium is also a layer of connective tissue, but it surrounds groups of 10 to 100 or more muscle fibers, separating them into bundles called fascicles (little bundles). Endomysium penetrates the interior of each fascicle and separates individual muscle fibers Fascicle from one another. Sarcolemma the plasma membrane of a muscle cell Sarcoplasm the cytoplasm of a muscle fiber; located within the sarcolemma Tendon a white fibrous cord of dense regular connective tissue that attaches muscle to bone.  Myofibril threadlike contractile elements within sarcoplasm of muscle fiber that extend entire length of fiber; composed of filaments Filaments or myofilaments are contractile proteins within myofibrils. Two types: thick filaments composed of myosin and thin filaments composed of actin Sarcomeres compartments arranged in the filaments (because it does not extend the entire length of a muscle fiber) inside the myofibril; the basic functional units of a microfibril Z discs are narrow; plate shaped regions of dense protein that separate sarcomeres Sarcoplasmic reticulum (SR) a fluid-filled system of membranous sacs encircling each myofibril Transverse (T) tubules thousands of tiny invaginations of the sarcolemma that tunnel in from the surface toward the center of each muscle fiber. When a skeletal muscle contracts, it moves one of the articulating bones. The two articulating bones usually do not move equally in response to contraction. One bone remains stationary or near its original position, either because other muscles stabilize that bone by contracting and pulling it in the opposite direction or because its structure makes it less movable. Origin the attachment of a muscle’s tendon to the stationary bone Insertion the attachment of the other muscle’s tendon to the movable bone * As a rule of thumb, in the limb the origin of a muscle is usually proximal and the insertion is usually distal. Anterior view Posterior view  Muscles of the head that produce facial expression Muscles of the head that produce facial expression