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Chapter 10, part 3

Chapter 10, part 3. Muscle Tissue. Tension production by skeletal muscles. Internal tension generated inside contracting muscle fibers External tension generated in extracellular fibers. Figure 10.16 Internal and External Tension. Figure 10.16. Motor units

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Chapter 10, part 3

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  1. Chapter 10, part 3 Muscle Tissue

  2. Tension production by skeletal muscles • Internal tension generated inside contracting muscle fibers • External tension generated in extracellular fibers

  3. Figure 10.16 Internal and External Tension Figure 10.16

  4. Motor units • All the muscle fibers innervated by one neuron • Precise control of movement determined by number and size of motor unit • Muscle tone • Stabilizes bones and joints

  5. Figure 10.17 The Arrangement of Motor Units in a Skeletal Muscle Figure 10.17

  6. Contractions • Isometric • Tension rises, length of muscle remains constant • Isotonic • Tension rises, length of muscle changes • Resistance and speed of contraction inversely related • Return to resting lengths due to elastic components, contraction of opposing muscle groups, gravity PLAY Animation: Whole Muscle Contraction

  7. Figure 10.18 Isotonic and Isometric Contractions Figure 10.18

  8. Figure 10.19 Resistance and Speed of Contraction PLAY Animation: Skeletal muscle contraction Figure 10.19

  9. SECTION 10-5Energy Use and Muscle Contraction

  10. Muscle Contraction requires large amounts of energy • Creatine phosphate releases stored energy to convert ADP to ATP • Aerobic metabolism provides most ATP needed for contraction • At peak activity, anaerobic glycolysis needed to generate ATP

  11. Figure 10.20 Muscle Metabolism Figure 10.20

  12. Figure 10.20 Muscle Metabolism Figure 10.20

  13. Energy use and level of muscular activity • Energy production and use patterns mirror muscle activity • Fatigued muscle no longer contracts • Build up of lactic acid • Exhaustion of energy resources

  14. Recovery period • Begins immediately after activity ends • Oxygen debt (excess post-exercise oxygen consumption) • Amount of oxygen required during resting period to restore muscle to normal conditions

  15. SECTION 10-6Muscle Performance

  16. Types of skeletal muscle fibers • Fast fibers • Slow fibers • Intermediate fibers

  17. Figure 10.21 Fast versus Slow Fibers Figure 10.21

  18. Fast fibers • Large in diameter • Contain densely packed myofibrils • Large glycogen reserves • Relatively few mitochondria • Produce rapid, powerful contractions of short duration

  19. Slow fibers • Half the diameter of fast fibers • Take three times as long to contract after stimulation • Abundant mitochondria • Extensive capillary supply • High concentrations of myoglobin • Can contract for long periods of time

  20. Intermediate fibers • Similar to fast fibers • Greater resistance to fatigue

  21. Muscle performance and the distribution of muscle fibers • Pale muscles dominated by fast fibers are called white muscles • Dark muscles dominated by slow fibers and myoglobin are called red muscles • Training can lead to hypertrophy of stimulated muscle

  22. Physical conditioning • Anaerobic endurance • Time over which muscular contractions are sustained by glycolysis and ATP/CP reserves • Aerobic endurance • Time over which muscle can continue to contract while supported by mitochondrial activities PLAY Animation: Muscle fatigue

  23. SECTION 10-7Cardiac Muscle Tissue

  24. Structural characteristics of cardiac muscle • Located only in heart • Cardiac muscle cells are small • One centrally located nucleus • Short broad T-tubules • Dependent on aerobic metabolism • Intercalated discs where membranes contact one another

  25. Figure 10.22 Cardiac Muscle Tissue Figure 10.22

  26. Functional characteristics of cardiac muscle tissue • Automaticity • Contractions last longer than skeletal muscle • Do not exhibit wave summation • No tetanic contractions possible

  27. SECTION 10-8Smooth Muscle Tissue

  28. Structural characteristics of smooth muscle • Nonstriated • Lack sarcomeres • Thin filaments anchored to dense bodies • Involuntary

  29. Figure 10.23 Smooth Muscle Tissue Figure 10.23

  30. Functional characteristics of smooth muscle • Contract when calcium ions interact with calmodulin • Activates myosin light chain kinase • Functions over a wide range of lengths • Plasticity • Multi-unit smooth muscle cells are innervated by more than one motor neuron • Visceral smooth muscle cells are not always innervated by motor neurons • Neurons that innervate smooth muscle are not under voluntary control

  31. You should now be familiar with: • The organization of muscle and the unique characteristics of skeletal muscle cells. • The structural components of the sarcomere. • The events at the neuromuscular junction. • The key concepts involved in skeletal muscle contraction and tension production. • How muscle fibers obtain energy for contraction. • Aerobic and anaerobic contraction, muscle fiber types, and muscle performance. • The differences between skeletal, cardiac and smooth muscle

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