Muscular system


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Muscular system

  1. 1. Muscular System Includes skeletal muscle tissues and tendons in the body. Skeletal muscles are specialized for contraction – they contain individual cells and connective tissues that conduct and distribute the forces generated.
  2. 2. Functions <ul><li>1.    Move elements of skeleton producing locomotion. </li></ul><ul><li>2.    Maintain posture and balance. </li></ul><ul><li>3.    Cradle and support soft tissues. </li></ul><ul><li>4.    Guard entrances and exits of the digestive tract. </li></ul><ul><li>5.    Assist in regulating blood flow through vessels. </li></ul><ul><li>6. Thermoregulation – heat produced by muscular contraction. </li></ul>
  3. 3. <ul><li>Origin – fixed, usually proximal end of muscle </li></ul><ul><li>Insertion – movable, usually distal end of muscle </li></ul><ul><li>Muscle must cross a joint to move bones </li></ul><ul><li>Prime mover – main muscle that performs a movement </li></ul><ul><li>Synergists – other muscles that assist the prime mover </li></ul><ul><li>Antagonists – muscles that oppose the prime mover – necessary for smooth movement. </li></ul>
  4. 4. Structure of Skeletal Muscle <ul><li>Fascia – </li></ul><ul><li>Tendon – </li></ul><ul><ul><li>continuous with Periosteum </li></ul></ul><ul><ul><li>aponeuroses – </li></ul></ul><ul><ul><ul><li>may be attached to fascia of other muscles </li></ul></ul></ul><ul><li>Belly - </li></ul>
  5. 5. Layers of c.t. <ul><li>Epimysium </li></ul><ul><li>Perimysium </li></ul><ul><ul><li>fascicles </li></ul></ul><ul><li>Endomysium </li></ul><ul><ul><li>Muscle fibers/cells </li></ul></ul>
  6. 7. Muscle fiber structure <ul><li>Sarcolemma – </li></ul><ul><li>Sarcoplasm – </li></ul><ul><li>Sarcoplasmic reticulum – </li></ul><ul><li>Transverse tubules – </li></ul><ul><li>Myofibrils </li></ul><ul><ul><li>Myosin filaments </li></ul></ul><ul><ul><li>Actin filaments </li></ul></ul>
  7. 8. Sarcomere <ul><li>functional unit of contraction </li></ul><ul><ul><li>Striations myosin actin </li></ul></ul><ul><li>Z-line </li></ul><ul><li>A bands </li></ul><ul><li>I bands </li></ul><ul><li>H-zone </li></ul><ul><li>M-line </li></ul>
  8. 11. Neuromuscular Junction <ul><li>Motor Neuron – </li></ul><ul><li>Motor end plate – specialization of sarcolemma with extensively folded membrane </li></ul><ul><li>Synaptic cleft – gap betw/ neuron and muscle cell </li></ul><ul><ul><li>Acetylcholine – neurotransmitter for muscles </li></ul></ul>
  9. 12. <ul><li>Motor unit – Motor neuron and the muscle fibers that it controls </li></ul><ul><li>Threshold stimulus – minimal strength needed to cause a contraction </li></ul><ul><ul><li>All or None response </li></ul></ul><ul><li>Recruitment – as more muscle power is needed, more motor units are stimulated </li></ul><ul><li>Muscle tone </li></ul>
  10. 13. Muscle Contraction <ul><li>The sarcolemma is stimulated by neurotransmitter chemicals and changes permeability. </li></ul><ul><li>Ca+ ions rush into the sarcoplasm from the transverse tubules. </li></ul><ul><li>Ca+ sticks to the actin causing it to change shape. </li></ul><ul><li>Myosin heads to grab onto actin fibers in the newly exposed attachment spots. </li></ul><ul><li>ATP makes the myosin heads flex dragging the actin with it. This happens repeatedly with many spots on the actin and myosin, and the sarcomere gets shorter. </li></ul>
  11. 14. Muscle Relaxation <ul><li>1.    The Ca+ is transported back out of the sarcoplasm. </li></ul><ul><li>2.    Myosin releases the actin. </li></ul><ul><li>3.    Opposing muscle action pulls the sarcomere back to its relaxed length. </li></ul><ul><li>*muscles can only pull (contract) not push. </li></ul>
  12. 15. Energy Sources for Contraction <ul><li>Mitochondria </li></ul><ul><ul><li>Hemoglobin </li></ul></ul><ul><ul><li>Myoglobin </li></ul></ul><ul><li>Creatine phosphate can recharge ATP </li></ul><ul><li>Lactic acid fermentation </li></ul><ul><ul><li>Muscle Fatigue </li></ul></ul>
  13. 16. Oxygen debt <ul><li>amount of oxygen needed by liver cells to convert lactic acid to glucose + what muscle cells need to resynthesize ATP and creatine phosphate and return them to their original concentrations </li></ul>
  14. 17. Cramp <ul><li>muscle contracts spasmodically but does not relax completely. Due to lack of ATP to move Ca++ ions back to the transverse tubules so that linkages between actin and myosin can be broken and muscle fibers can relax </li></ul>
  15. 18. Rigor Mortis <ul><li>Actin and myosin fibers linked due to increased membrane permeability to Ca++ ions and decrease in ATP. Prevents relaxation. Rigor mortis sets in a few hours after death and lasts until muscles begin to decompose; about 72 hours </li></ul>