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2013-07-08 00:00:02

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  1. Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for
  2. The dense layer of connective tissue that surrounds an entire skeletal muscle is the
  3. A fascicle is
    a group of muscle fibers that are encased in the perimysium
  4. The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a
  5. In a sarcomere, thick filaments are linked laterally by proteins of the
    M line
  6. The repeating unit of a skeletal muscle fiber is the
  7. Muscle fibers differ from "typical cells" in that muscle fibers
    have many nuclei
  8. The region of the sarcomere containing the thick filaments is the
    A band
  9. Each skeletal muscle fiber contains ________ myofibrils
    hundreds to thousands
  10. The thin filaments of striated muscle are made primarily of which proteins?
    nebulin, tropomyosin, troponin, actin
  11. Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. What mechanism ensures a rapid and efficient removal of acetylcholine?
    Acetylcholine is degraded by acetylcholinesterase.
  12. The neuromuscular junction is a well-studied example of a chemical synapse. Describe a critical event that occurs at the neuromuscular junction
    Acetylcholine is released by axon terminals of the motor neuron.
  13. Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons
    extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber
  14. Calcium entry into the axon terminal triggers which of the following events?
    Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.
  15. Acetylcholine binds to its receptor in the sarcolemma and triggers __________.
    the opening of ligand-gated cation channels
  16. Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?
    The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.
  17. Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?
    Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.
  18. Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?
    Calcium release from the sarcoplasmic reticulum initiates the contraction.
  19. A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?
    A series of proteins that control calcium release.
  20. What is name given to the regularly spaced infoldings of the sarcolemma?
    transverse or T tubules
  21. Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?
    Calcium ions
  22. What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?
    Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.
  23. The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?
    A myosin head bound to actin
  24. What structure is the functional unit of contraction in a skeletal muscle fiber?
    The sarcomere
  25. Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber?
    Calcium ions are stored in the sarcoplasmic reticulum
  26. After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?
    ATP binds to the myosin head.
  27. How does the myosin head obtain the energy required for activation?
    The energy comes from the hydrolysis of ATP.
  28. What specific event triggers the uncovering of the myosin binding site on actin?
    Calcium ions bind to troponin and change its shape.
  29. When does cross bridge cycling end?
    Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.
  30. In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
    acetylcholine (ACh)
  31. When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
    voltage-gated calcium channels
  32. What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
  33. The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
    Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.
  34. How is acetylcholine (ACh) removed from the synaptic cleft?
    acetylcholinesterase (AChE; an enzyme)
  35. The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?
    terminal cisternae of the sarcoplasmic reticulum
  36. Inside a muscle, bundles of single muscle fibers form __________.
  37. The muscle action potentials that initiate contraction are transmitted from the sarcolemma into the interior of the muscle fiber by __________.
    T tubules
  38. T tubules and the terminal cisternae are clustered into structures called __________
  39. The sarcoplasmic reticulum contains __________
  40. Which organelle completely surrounds each myofibril inside a muscle fiber?
    sarcoplasmic reticulum
  41. To what regulatory protein does calcium bind during the initiation of the contraction cycle in skeletal muscle fibers?
  42. What causes the active site on actin to be exposed or uncovered?
    tropomyosin shifting position
  43. Describe excitation in the context of excitation-contraction coupling in skeletal muscle?
    the generation of an action potential in the sarcolemma
  44. Describe how excitation is coupled to contraction in skeletal muscle fibers?
    through calcium release from the sarcoplasmic reticulum
  45. Malignant hyperthermia (MH) is a rare genetic disease in which the sarcoplasmic reticulum leaks calcium when the patient is put under general anesthesia. How would anesthesia affect the skeletal muscles of a patient with MH?
    The muscles would contract because of calcium binding to troponin.
  46. The most important factor in decreasing the intracellular concentration of calcium ion after contraction is
    active transport of calcium into the sarcoplasmic reticulum
  47. How would the loss of acetylcholinesterase from the motor end plate affect skeletal muscle?
    It would cause spastic paralysis (muscles are contracted and unable to relax)
  48. What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
    arrival of an action potential
  49. The binding of calcium to which molecule causes the myosin binding sites to be exposed?
  50. A myosin head binds to which molecule to form a cross bridge?
  51. What causes the myosin head to disconnect from actin?
    binding of ATP
  52. What energizes the power stroke?
    hydrolysis of ATP
  53. When a muscle is stimulated repeatedly at a high rate, the amount of tension gradually increases to a steady maximum tension. This is called
    complete tetanus
  54. The increase in muscle tension that is produced by increasing the number of active motor units is called
  55. A resting muscle generates most of its ATP by
    aerobic metabolism of fatty acids
  56. After heavy exercise, if energy reserves in a muscle are depleted, ________ occurs.
    an oxygen debt
  57. At peak levels of muscle exertion the mitochondria can supply
    only about one-third of the energy required by the muscle
  58. The type of muscle fiber that is most resistant to fatigue is the ________ fiber.
  59. Muscles that move the eyeball have
    fast fibers
  60. Fast muscle fibers can adapt to aerobic metabolism by generating more mitochondria in response to
    repeated, exhaustive stimulation
  61. Which type of muscle fibers are best adapted for prolonged contraction such as standing all day?
    slow fibers