Anatomy & Physiology

Anatomy & Physiology Study Guide With fibrosis, the muscle loses flexibility, and the collagen fibers restrict movement and circulation. The ability to tolerate exercise decreases. The muscle fatigues quickly and has decreased ability to recover from injury. A reduction in the number of satellite cells continues to decrease with age, and the amount of fibrous tissue increases. When an injury occurs, the capability to repair is limited and excess scar tissue is the usual result. 11.7 Chapter Eleven Review Fascicle arrangement is associated with muscle power and range of motion: • Structural variations among skeletal muscles affect their power, range, and speed of movement. • A muscle can be classified as a parallel muscle, convergent muscle, pennate muscle, or circular muscle (sphincter) according to the assembly of fibers and fascicles in it. A pennate muscle may be unipennate, bipennate, or multipennate. The three classes of levers increase muscle effectiveness: • Levers are classified as first-class, second-class, or third-class levers. Third-class levers are the most common levers in the body. • A lever is a rigid structure that moves around a fixed point called the fulcrum. Levers can change the direction and effective strength of an applied force, and the distance and speed of the movement produced. Muscle origins are at the immobile end of muscles, whereas insertions are at the movable end of muscles: • Each muscle can be classified by its origin, insertion, and action. • The site of attachment of the fixed end of a muscle is called the origin; the site where the movable end of the muscle attaches to another structure is called the insertion. • The movement produced when a muscle contracts is its action. • Depending on the function of its action, a muscle can be classified as an agonist (or prime mover), an antagonist, a synergist, or a fixator. Descriptive terms are used to name skeletal muscles: • The names of muscles commonly provide clues to their body region, origin and insertion, fascicle organization, relative position, structural features, and action. • Innervation refers to the allocation of nerves that control a region or organ, including a muscle. Axial muscles are muscles of the head and neck, vertebral column, trunk, and pelvic floor. Appendicular muscles are muscles of the shoulders, upper limbs, pelvic girdle, and lower limbs.

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