Review motor end plate nmj notes


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Review motor end plate nmj notes

  1. 1. Review of Terminology (the “ sarco- ” words) <ul><li>Sarcolemma – the cell membrane of a muscle fiber. </li></ul><ul><li>Sarcoplasm – the cytoplasm of a muscle fiber. </li></ul><ul><li>Sarcoplasmic reticulum – the endoplasmic reticulum of a muscle fiber. </li></ul><ul><li>Sarcomere – the smallest unit of contraction within a myofibril. </li></ul>
  2. 2. Sarcomere Sarcolemma Sarcoplasmic Reticulum A similar picture can be found on page 169 of the reading packet, figure 8.4. * Note that the sarcoplasmic reticulum “surrounds” each myofibril. * Also note that the sarcoplasmic reticulum seems to form repeating units that “surround” individual sarcomeres . Z-line Z-line
  3. 3. Review of Terminology (the “myo-” words) <ul><li>Myocytes – a muscle fiber or cell. </li></ul><ul><li>Myofibrils – units of alternating filamentous proteins contained within the sarcoplasm of a muscle fiber and which extend from end to end within the fiber. </li></ul><ul><li>Myofilaments – filamentous proteins called actin (thin) filaments and myosin (thick) filaments. </li></ul>
  4. 4. sarcomere Myofibril * Note that a sarcomere is a repeating unit of contraction within the myofibril. * The myofibril can be seen to be made up of repeating units of overlapping myofilaments .
  5. 5. Myofilaments <ul><li>Thick myofilament </li></ul><ul><ul><li>Myosin </li></ul></ul><ul><li>Thin myofilament </li></ul><ul><ul><li>Actin </li></ul></ul><ul><li>Arrangement is so orderly that the muscle looks striped or “ striated ” microscopically </li></ul>sarcomere sarcomere lengthened shortened
  6. 6. New Terminology <ul><li>T-tubules – extensions of the sarcolemma which carry “electrical” impulses deep within a muscle fiber. </li></ul><ul><li>This allows the impulse to be brought very close to the sarcoplasmic reticulum throughout the fiber, and thus to get very close to each and every sarcomere. </li></ul>
  7. 7. Skeletal Muscle Fiber (Myocyte) sarcoplasmic reticulum (the “blue” tubes) T-tubules (the “purple” tubes) Myofibril A similar picture can be found on page 169 of the reading packet, figure 8.4. Sarcolemma
  8. 8. Motor Unit (page 170; figure 8.6) <ul><li>Defined as a motor neuron and all the muscle fibers it innervates </li></ul><ul><li>By using more motor units, the muscle contracts with more force. </li></ul><ul><li>A small number are used in muscles with fine control </li></ul><ul><li>A large number are used in muscles with crude control </li></ul>
  9. 9. Neuromuscular Junction (page 170; figure 8.5) <ul><li>This is defined as the place where the motor neuron axon “connects” to the muscle fiber. </li></ul><ul><li>It is also the site where the motor neuron stimulates the muscle fiber to begin the sequence known as Action Potential and eventually contraction . </li></ul>Signal from brain Motor end plate
  10. 10. Axon branch of motor neuron Motor End Plate Neuromuscular Junction
  11. 11. Our Goals !! <ul><li>1. To define and track the sequence of “electrical” events which happen in a phenomenon called “ Action Potential ”. </li></ul><ul><li>2. To define and track the sequence of interactions between myofilaments that occur during contraction and relaxation of muscle tissue. </li></ul><ul><li>3. To determine the connections between numbers one and two above. </li></ul>