Chapter 20 MOVEMENT

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review questions

Background from Introductory Biology Courses

  1. Biology websites
    1. The mechanism of filament sliding during contraction of a myofibril
  2. Hole's Human Anatomy and Physiology
    1. Muscular System
      1. Action Potentials and Muscle Contraction
      2. Action Potentials and ...
      3. Breakdown of ATP and C...
      4. Chemical Synapse
      5. Electron Transport Sys...
      6. Function of the Neuromuscular...
      7. Myofilament Contraction
      8. Sarcomere Contraction
      9. Sarcomere Shortening
      10. Transmission Across a ...
  3. On-Line Biology Book by M. J. Farabee 
    1. Muscular and Skeletal Systems
  4. Kimball's Biology Pages
    1. Muscles from Kimball's Biology Pages

MUSCLE and MOVEMENT Lecture Slides

  1. Movement
    1. Locomotion
    2. Repositioning
    3. Internal movement
    1. Muscle Cells
      1. Contractile cell unique to animals
      2. Made of myocytes (muscle cells)
      3. Types of muscles
        1. Striated
          1. Skeletal and cardiac
        2. Smooth
      4. Image from Wikipedia

    1. The musculoskeletal system
    2. Skeletal Muscle
      1. Figure 20.1a  The organization of skeletal muscles
      2. Figure 20.1b  The organization of skeletal muscles: MUSCLE FIBERS
      3. Figure 20.1c  The organization of skeletal muscles: MYOFYBRILS and SARCOMERES

     

    CLICK on image to enlarge
    Image of skeletal muscle organization from Wikipedia. 

    1. Figure 20.1  The organization of skeletal muscles (Part 4)
    2. Sarcomeres
    3.  
      1. Thick filaments: myosin
      2. Thin filaments: actin
      3. troponin and tropomyosin
      1. Picture from Wikipedia

     

  1. Skeletal Muscle Organization
  2. Figure 20.3  Muscle contraction produced by sliding filaments
    1. Muscle contracts when thick filaments slide relative to the thin filaments
  3. Sliding Filament Mechanism
  4. Muscle, How It Works: Contraction
    1. STRUCTURE OF SARCOMERE
  5. Figure 20.4  Myosin molecules form the thick filament
  6. Thick Filament Structure
    1. Globular heads contain
    2. actin binding sites
    3. ATP-hydrolyzing sites
    4. Heads form cross-bridges with actin
       

    1. Fig 20.5  Molecular interactions that underlie muscle contraction
      1. Image from Wikipedia
    2. Fig 20.5  Molecular interactions that underlie muscle contraction
      1. Rigor Conformation
      2. Breaking the Cross-bridge
    3. Fig. 20.5  Molecular interactions that underlie muscle contraction
      1. Hydrolyzing the ATP (ADP + unreleased Pi) causes the angle of the head to change (cocking)
      2. And bind to the actin

    4. Fig 20.5  Molecular interactions that underlie muscle contraction
      1. The myosin head swivels, pulling the attached actin toward the midline (power stroke)

      2. The myosin unbinds the ADP and remains bound to the actin (rigor) until a new molecule of ATP binds to the myosin head (Step 2)

    5. Fig 20.5  Molecular interactions that underlie muscle contraction
    6. Thin filament structure and composition
    7. Figure 20.6  The regulation of contraction
      1. TROPOMYOSIN
      2. TROPONIN
    8. Figure 20.6  The regulation of contraction
      1. Ca2+ binds to troponin
      2. Troponin-Ca2+ complex removes tropomyosin blockage of actin sites
      3. Heads of thick filament (containing preexisting myosin-ATP complex) form cross bridges to actin strand
      4. Cross bridges swivel as ATP is hydrolyzed and ADP is released
      5. Contraction occurs.
    9. Muscle, How It Works: Contraction
    10. MUSCLE, HOW IT WORKS
      1. Stimulation Contraction Relaxation
    11. The T system of Muscle cells
    12. Sarcoplasmic Reticulum (SR)
      1. Source of calcium ions that are released upon the impulse to contract.
    13. Terminal cisternae
      1. The impulse to contract is conducted from the T tubule to the SR via the terminal cisternae
    14. Figure 20.7  Excitation-contraction coupling
      1. Contraction is initiated when a nerve impulse reaches the motor endplate at the neuromuscular junction 
    15. Acetocholene (Ach) released at the motor endplate diffuses across the synaptic space
    16. Ach attaches to Ach receptors on the sarcolemma, opening Na channels
    17. Action potential is propagated
    18. Calcium Storage in the SR
 
  1. Figure 20.7  Excitation-contraction coupling
    1. Depolarization of T-tubules causes the SR to depolarize and release Ca++ to the sarcoplasm. <p>
  2. Ca2+ diffuses to thin filament and binds to troponin
    1. Troponin-Ca2+ complex removes tropomyosin blockage of actin sites
    2. Depolarization of T-tubules causes the SR to depolarize and release Ca++ to the sarcoplasm.
    3. Ca2+ diffuses to thin filament, binds to troponin
    4. Troponin-Ca2+ complex removes tropomyosin blockage of actin sites
  3. AChE (Acetylcholinesterase) hydrolyzes ACH and the membrane repolarizes, terminating the action potential
  4. Figure 20.7-7 Calcium is bound to the troponin
    1. Cross-bridge cycling
  5. Skeletal Muscle Contraction: Relaxation
  6. Whole Muscle Mechanics
  7. Myogram: graph of a muscle contraction.
  8. Latent period is the time it takes for AP to reach Voltage Gated Ca2+ channels and for Ca2+ to increase in the sarcoplasm
  9. Relaxation is the sequestering of Ca2+ in the sarcoplasmic reticulum
  10. Muscle Contractions
  11. Muscle Twitch
    1. Single all-or-none contraction
    2. twitch contraction lasts from 20 to 200 msec
  12. Wave Summation
  13. Complete and Incomplete Tetanus
  14. Tetany
  15. Clostridium tetani
    1. Tetanus or lockjaw is spastic paralysis
    2. Bacterial toxin blocks the neurotransmitters GABA and glycine in the spinal cord & causes overstimulation of the muscles
    3. Prevents the inhibition of contraction of opposing sets of muscles
  16. Fig. 19.11: Length-Tension Relationship
    1. Tension depends on the length of the muscle when stimulated.
    2. Force generated is associated with starting length of muscle
    3. Muscle tension is greatest when muscle is at its ideal starting length.
  17. Figure 20.11  The relationship between the length and the tension produced by skeletal muscle
  18. Box 20.1  The electric eel Electrophorus electricus possesses both strong and weak electric organs
    1. Electric organs - modified skeletal muscle
    2. Electrocytes - stacked in columns
    3. Respond to signals from motor neurons
    4. All electrocytes in column depolarize spontaneously
    5. Up to 600 V discharge
  19. Energy Sources for Contraction
  20. Figure 20.13  The production and use of ATP
    1. ATP: produced by cellular respiration
    2. Aerobic catabolism: efficient, slow ATP generation
    3. only enough free ATP for 2-4 seconds of work (about 10 contraction)
  21. Energy Sources for Contraction
    1. Creatine Phosphate:
    2. only enough for about a 100 yard dash (10-20 seconds)
    3. When ATP is plentiful, creatine phosphokinase in the mitochondria stores excess energy as creatine phosphate
  22. Production of ATP
  23. Oxygen Debt
    1. Lactic acid is converted to pyruvic acid
      1. Liver cells convertpyruvic acid to glucose using ATP energy.
      2. Pyruvic acid directly enters the Kreb's cycle
    2. Oxygen debt is the amount of oxygen needed for either process
  24. The cause of fatigue
    1. During intense exercise, vertebrate skeletal muscles produce lactic acid, which results in cellular acidification. This appears related to fatigue, but the actual mechanism remains unclear (build up of Ca2+ and depletion of phosphocreatine may play a role).
  25. The cause of fatigue
    1. During less intense exercise, muscles run out of glycogen and become dependant upon blood glucose. The efficiency of this transfer are associated with fatigue.
  26. Classification of Skeletal Muscle Fibers: Tonic fibers
  27. Twitch muscle fibers
    1. generate muscle contractions (twitches) through Action Potentials
    2. Fast glycolytic (FG): Can split ~600 ATPs per second
    3. Fast oxidative [glycolytic] (FO[G]): intermediate between FG and SO
    4. Slow oxidative (SO): Can split ~300 ATPs per second
  28. Fast glycolytic fibers (FG)
    1. Contract quickly, generate lots of power.
    2. Mainly fueled by glycolysis;
    3. high levels of glycolytic enzymes & low mitochondrial volume.
  29. Slow oxidative fibers (SO): 
    1. Contract relatively slowly. primarily fueled by oxidative metabolism, high levels of aerobic enzymes and lots of mitochondria and myoglobin.
    2. High levels of myoglobin and mitochondria make SO fibers more resistant to fatigue
    3. SO fibers for endurance
  30. Muscle fiber diversity: Muscle fiber diversity is plastic, to a degree.
    1. All vertebrates have a mixture of fibers, but some species are adapted to have significantly more SO fibers (e.g. western toad) or more FG fibers (e.g. leopard frog).
    2. Even individuals of a species are born with a certain ratio of fibers. This ratio can be changed by exercise, but not completely reversed.
  31. Figure 20.14  Whole muscles typically consist of mixtures of different types of fibers
    1. Most muscles contain a combination of both FG and SO muscles.
    2. For example, the calf muscle of a cat contains: 45% FG and 25% SO (the other portion are intermediate fibers).
  32. Whole muscles typically consist of mixtures of different types of fibers
  33. Fish contain both red muscle (SO) and white muscle (FG).
    1. The SO muscle is for steady swimming performance.
    2. The FG muscle is for chase/escape performance.
  34. Table 20.2
  35.  
  36. The Motor Unit
  37. Motor Unit
  38. Figure 20.15  Vertebrate skeletal muscles consist of many different, independent motor units
    1. Total strength of a contraction depends on how many motor units are activated & how large the motor units are.
  39. Why you should never arm wrestle a chimpanzee
    1. Alan Walker,"The Strength of Great Apes and the Speed of Humans," Current Anthropology, April 2008.
  40. Graded Contraction
  41. Muscle Force
  42.  MUSCLE, HOW IT IS USED
  43. Skeletal muscle
  44.  
  45. Cardiac Muscle
    1. Cardiac Muscle looks like striated muscle but is different in a couple ways.
    2. Image from Wikipedia

     

  46.  
  47. Smooth Muscle
    1. Smooth Muscle: Image from Wikipedia

 

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