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Muscle Outline

Muscle Outline - Chapter 10 Muscle Tissue I Skeletal Muscle...

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Chapter 10: Muscle Tissue I. Skeletal Muscle Tissue and the Muscular System, p. 284 Skeletal muscles are the muscles attached to the skeletal system, which allow us to move. The muscular system includes only skeletal muscles. Skeletal muscles are made up of muscle tissue (composed of muscle cells or fibers), connective tissues, nerves and blood vessels. The 5 functions of skeletal muscles are: 1. To produce skeletal movement. 2. To maintain posture and body position. 3. To support soft tissues. 4. To guard the entrances and exits of the body. 5. To maintain body temperature. II. Functional Anatomy of Skeletal Muscle, p. 284 Organization of Connective Tissues, p. 284 Muscles have 3 layers of connective tissues: 1. the epimysium : an exterior collagen layer connected to the deep fascia which separates the muscle from surrounding tissues. 2. the perimysium : surrounds bundles of muscles fibers called fascicles . Perimysium holds the blood vessels and nerves that supply the fascicles. 3. the endomysium : surrounds individual muscle cells (the muscle fibers ), and contains the capillaries and nerve fibers that directly contact the muscle cells. Endomysium also contains satellite cells (stem cells) that repair damaged muscles. At each end of the muscle, the endomysium, perimysium and epimysium come together to form a connective tissue attachment to the bone matrix, either a tendon (a bundle) or an aponeurosis (a sheet). Blood Vessels and Nerves, p. 285 Skeletal muscles are voluntary muscles, controlled by nerves from the central nervous system. An extensive vascular system supplies large amounts of oxygen to muscles, and carries away wastes. Skeletal Muscle Fibers, p. 286 Skeletal muscle cells (fibers ) are very different from typical cells. The long fibers develop through the fusion of mesodermal cells (myoblasts ) until they become very large and contain hundreds of nuclei. The cell membrane of a muscle cell is called the sarcolemma , which surrounds the sarcoplasm or cytoplasm of the muscle fiber. Muscle contractions begin with a change in the transmembrane potential. Because the whole muscle fiber must contract at the same time, the signal (action potential ) is conducted through the cell by transverse tubules (T tubules ) which have the same properties as the sarcolemma. Within each muscle fiber are hundreds of lengthwise subdivisions called myofibrils . Myofibrils are made up of bundles of the protein filaments (myofilaments ) that are responsible for muscle contraction. The 2 types of myofilaments are: 1. thin filaments : made of the protein actin , and 2. thick filaments : made of the protein myosin . Sarcoplasmic Reticulum : Surrounding each myofibril is a membranous structure called the sarcoplasmic reticulum , which is involved in transmitting the action potential to the myofibril. The sarcoplasmic reticulum is similar in structure to the smooth endoplasmic reticulum, forming chambers called terminal cisternae which attach to T tubules. One T tubule and a pair of terminal cisternae are called a triad .
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Ion pumps concentrate calcium ions (Ca++) in the cisternae. The calcium ions are released into the
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Muscle Outline - Chapter 10 Muscle Tissue I Skeletal Muscle...

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