Chapter 9 (Skeletal Muscle Tissue)

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Chapter 9 (Skeletal Muscle Tissue)
2014-10-08 13:43:01
Anatomy Physiology

Chapter 9 (Skeletal Muscle Tissue)
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  1. Define three types of muscle tissue?
    Skeletal muscle tissue, smooth muscle tissues, and cardiac muscle tissue.
  2. What is skeletal muscle tissue?
    Moves the body by pulling on bones of the skeleton making it possible for us to walk dance, bite and apple, or play the guitar.
  3. What is smooth muscle tissue?
    Contractions move fluid and solids along the digestive tract and regulate the diameters of small arteries among other functions.
  4. What is cardiac muscle tissue?
    Contractions move blood within the heart and through the blood vessels.
  5. What are the six functions of skeletal muscle tissue?
    Produce skeletal movement, maintain posture and body position, support soft tissues, guard body entrances and exits, maintain body temperature, and provide nutrient reserves.
  6. What are three levels of the skeletal muscle structure?
    Epimysium, perimysium, and endomysium.
  7. What is epimysium?
    Surrounds skeletal muscles and is a dense layer of collagen fibers.
  8. What is perimysium?
    Connective tissue partition that separates adjacent fasciculi in skeletal muscle.
  9. What is endomysium?
    A delicate network of connective tissue fibers that surround individual muscle cells.
  10. What is the difference between sarcolemma
    and the sarcoplasm?
    Skeletal muscle fibers have a plasma membrane called a sarcolemma, and a cytoplasm surrounding the myofibrils called sarcoplasm.
  11. What is the definition of a sarcomere?
    Is the smallest contractile unit of a striated muscle cell.
  12. What is an A band?
    Is the dense region of the sarcomere that contains thick filaments.
  13. What is an I band?
    Contains thin filaments but no thick filaments, extends from the A band of one sarcomere to the A band of the next.
  14. What is an H band?
    Is lighter region on either side of the M line. The H band contains thick filaments, but no thin filaments.
  15. What is the M line?
    Connects the central portion of each thick filament.
  16. What is the Z line?
    Mark the boundary between adjacent sarcomeres. Contain actinins.
  17. What are F-actin?
    Is a twisted strand of individual G-actin molecules.
  18. These thin filaments are attached to the Z line by what?
  19. What are T tubules?
    Extension of the sarcolemma into the sarcoplasm.
  20. What is tropomyosin?
    Cover the active sites on G-actin and prevent actin-myosin interaction. A tropomyosin molecule is  double stranded protein that is bound to one molecule of troponin midway along its length.
  21. What is troponin?
    Is bound to tropomyosin and also has one site bound to G-actin, and two sites for Ca2+ ions.
  22. What is free head?
    Has two globular protein subunits, and a connection between the two that acts as a hinge.
  23. The myosin molecule has this bound to other myosin molecules?
  24. What is titan?
    Fibrous protein that connects thick myosin filaments to the z lines in the sarcomere.
  25. What thick filaments contain these molecules and they are arranged with their tails pointing toward the M line?
    Myosin Molecules.
  26. Describe sliding filament theory?
    When a skeletal muscle fiber contracts, thin filaments slide past thick filaments. This occurs in every sarcomere along a myofibril, so the myofibril gets shorter. When myofibril gets shorter so does the muscle fiber.
  27. Describe action potential?
    In neurons and skeletal muscle fibers, the depolarization produces an electrical impulse or action potential that us spread or propagated along their plasma membranes.
  28. What is neuromuscular junction?
    Is located midway along the muscle fibers length. It is made up of an axon terminal of a motor neuron, a specialized region of the sarcolemma called the motor end plate and, in between, a space called the synaptic cleft.
  29. The action potential sweeps down each T tubule to the terminal cisternae causing the SR to release Ca2+. It triggers the contraction of the muscle fibers, what is this event called?
    Excitation-contraction coupling.
  30. What are the six steps of contraction cycle?
    Contraction cycle begins, active sites exposed, cross-bridges form, myosin heads pivot, cross-bridges detach, and myosin reactivates.
  31. What happens in Contraction cycle begins?
    Arrival of calcium ions within the zone of overlap in a sarcomere.
  32. What happens in active sites exposed?
    Calcium ions bind to troponin, weakening the bond between actin and the troponin-tropomyosin complex. They then changed position, rolling tropomyosin molecule away from active sites on actin, allowing interaction with the energized myosin heads.  
  33. What happens in cross-bridges form?
    Once the active sites are exposed, the energized myosin heads bind to them, forming cross-bridges.
  34. What happens in myosin heads pivot?
    After the cross-bridges form, the energy that was stored in the resting state is released as the myosin heads pivot toward the M line. This action is called the power stroke; when it occurs, the bound ADO and phosphate group are released.
  35. What happens in cross-bridges detach?
    When another ATP binds to the myosin head, the link between the myosin head and the active site on the actin molecule is broken. The active site is now exposed and able to form another cross-bridge.
  36. What happens in myosin reactivates?
    Myosin reactivates when the free myosin head splits ATP into ADP and P. The energy released is used to "recock" the myosin head.
  37. What are the six steps in excitation-coupling?
    Neural control, excitation, calcium ions release, contraction cycle begins, sarcomere shorten, and muscle tension produced.
  38. What happens in neural control?
    A skeletal muscle fiber contracts when stimulated by a motor neuron at a neuromuscular junction. The stimulus arrived in the form of an action potential at the axon terminal.
  39. What happens in excitation?
    The action potential causes the release of ACh into the synaptic cleft, which leads to excitation--the production of an action potential in the sarcolemma.
  40. What happens in calcium ion release?
    The muscle fiber action potential travels along the sarcolemma and into T tubules down to the triads. This triggers the release if Ca2+ from the terminal cisternae if the sarcoplasmic reticulum.
  41. What happens contraction cycle begins?
    The contraction cycle begins when the Ca2+ bind to troponin, exposing the active sites on the thin filaments. This allows cross-bridge formation and will continue as long as ATP is available.
  42. What happens in sarcomeres shorten?
    As the thick and thin filaments interact, the sarcomere shorten pulling the ends of the muscle fiber closer together.
  43. What happens in muscle tension is produced?
    During the contraction, the entire skeletal muscle shortens and produces a pull, or tension, on the tendons at either end.
  44. What phases happens in a muscle twitch?
    Latent period, contraction phase, and relaxation phase.
  45. What happens in latent period?
    During this period, and action potential sweeps across the sarcolemma, and the sarcoplasmic reticulum releases calcium ions. The muscle fiber does not produce tension during the latent period, because the contraction cycle has yet to begin.
  46. What is the contraction phase?
    Tension rises to a peak. As the tension rises, calcium ions are binding to troponin, active sites on thin filaments are being exposed, and cross-bridge interactions are occurring.
  47. What happens in the relaxation phase?
    During this period, calcium levels are falling, active sites are being covered by tropomyosin, and the number of active cross-bridges is declining as they detach. As a result, tension returns to resting levels.
  48. What is the difference between complete tetanus and  incomplete tetanus?
    A muscle producing almost peak tension during rapid cycles of contraction and relaxation is in incomplete tetanus. Complete tetanus occurs when the relaxation phase is eliminated.
  49. All the muscle fibers controlled by a single moor neuron is a?
    Motor unit.
  50. Increasing the number of active motor units is called?
  51. What is the difference between isotonic and isometric?
    In isotonic concentration the tension in the muscle rises and the length of the muscle changes. In isometric the tension rises, but not the length of the muscle.
  52. What is the difference between concentric and eccentric?
    In concentric contractions the muscle shortens. In eccentric contractions the load is greater than peal tension, the muscle lengthens.
  53. What factors cause muscle fatigue?
    • Decline in pH (7.1 to 6.4).
    • Decreasing calcium ion binding to troponin and altering enzymes activities.
  54. List the types of skeletal muscle fibers?
    Fast, slow, and intermediate fibers.
  55. What are intermediate fibers?
    Are very similar to fast fibers, but have a greater resistance to fatigue.
  56. What are slow fibers?
    Are smaller in diameter, slower in contraction speed, contain more capillaries and mitochondria, and also contain the red oxygen-carrying pigment myoglobin.
  57. What are fast fibers?
    Are large in diameter, and contain densely packed myofibrils, large glycogen reserves, and relatively few mitochondria. They contract rapidly and powerfully are supported by anaerobic metabolism, and fatigue easily.