MusculoSkeletal

MusculoSkeletal - THE MUSCULOSKELETAL SYSTEM (Textbook...

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THE MUSCULOSKELETAL SYSTEM (Textbook Chapters 8 and 9)
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THREE TYPES OF MUSCLE 1. SMOOTH MUSCLE OF VISCERAL MUSCLE 2. CARDIAC MUSCLE 3. SKELETAL MUSCLE (See FIGURE 8.1) MAIN FUNCTIONS FOR HOMEOSTASIS 1. Movement 2. Support - e.g. postural muscles, proper posture also helps breathing, vision, circulation. Also protects soft tissues. 3. Heat Production - Rhythmic cycling of postural muscle contractions maintains body temperature at rest. Skeletal muscle is about one-third of total body mass. DETERMINING AGE CHANGES Often difficult to separate true and direct age changes from those that result from disuse (lack of exercise), altered neural innervation, circulatory changes, or respiratory changes. SKELETAL MUSCLE CELLS Muscle Cells + nerve cells, collagen, elastin, fat, blood vessels = a muscle See FIGURE 8.2 See FIGURE 8.2 Cell Membrane (Sarcolemma) - See FIGURE 8.3 Convoluted large surface area of motor end plate receives nervous stimulation. Sarcolemma carries action potentials. T tubules deliver action potentials deep within cell. 2
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- See FIGURE 8.4 Contraction - Action potential is received at the motor end plate. As action potential passes over the sarcolemma the sarcoplasmic reticulum releases calcium. The Ca 2+ causes the thick myosin filaments to pull on the thin actin filaments and slide along them making the muscle shorter. Note that each Sarcomere shortens. Since muscle is connected to bone, the shortening of muscle causes bone to move. FIGURE 8.5. Some of the energy (ATP) used in contraction is released as heat. Age Changes in Muscle Cells Internal Components - Convolutions of motor end plate decrease and sarcolemma becomes smoother. This decrease in surface area diminishes excitability. Other sarcolemmal changes make action potentials weaker, slower, and irregular. All these changes make muscle cells take longer to begin contractions and need more time to recover between contractions. Results include longer response time when you want to move; diminished ability to perform rapid, repeated motions; and decreased maximum strength. Decreased number of sarcomeres with age makes muscles shorter. This diminishes range of motion, makes people stiffer, and further reduces muscle strength: exercise can help delay or diminish such changes. Lack of exercise causes deterioration in mitochondrial, and glycolytic, energy production (ATP) - this severely decreases endurance capacity. Cell Thickness - Lack of exercise causes decreased muscle thickness but with regular exercise there is little change until about age 75. Even after 75, those who exercise regularly and rigorously show little loss of muscle mass. Cell Number - Number of muscle cells drops with age, (no reproduction) but in exercised muscle the remaining cells thicken and take on extra work. In non-exercised muscles the spaces are filled with fat and fibrous tissue, and the muscle gets progressively weaker. Cell Repair
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This note was uploaded on 01/16/2011 for the course GERO 310 taught by Professor Davies during the Fall '09 term at USC.

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MusculoSkeletal - THE MUSCULOSKELETAL SYSTEM (Textbook...

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