Physiology of skeletal ms

  1. Striated Muscle: definition and type
    The contractile apparatus is highly organized into sarcomere structures giving a “striated” appearance under the microscope.

    –Skeletal Muscle performs mechanical work via the skeleton under voluntary neural control.

    –Cardiac Muscle performs mechanical work in the heart under its own pacing control modulated by the autonomic nervous system.
  2. Smooth Muscle
    •The contractile apparatus is loosely organized without a defined banding pattern.

    –Smooth muscle performs mechanical work in many target organ systems and is modulated by neurotransmitters, metabolic, local and hormonal factors.
  3. Equilibrium of Forces
    insufficient because in order to hold up 10kg ball, the bicep has to produce 70kg force
  4. The lever system of the arm amplifies...
    the velocity and range of movement.
  5. General Features of Skeletal Muscle
    •Muscle cells (fibers) are multinucleated, striated and organized in parallel bundles.

    • •Diameters range from 10 mm - 100 mm;
    • lengths range from 1 mm - 20 cm. 

    • •Individual muscle fibers are activated by motor neurons from the central nervous system (spinal cord) at neuromuscular
    • junctions leading to muscle action potentials and voluntary contraction.
  6. organization of skeletal ms
    muscle --> ms fiber --> myofibril
  7. what is in ECM of skeletal ms?
    collagen, intermediate filament and dystrophin
  8. the basic repeating contractile units in striated muscle: both skeletal and cardiac
  9. What are the contractile proteins found in sarcomere?
    myosin, tropomyosin, troponin and actin
  10. Shorten Sarcomeres & Muscle Fibers involves ...
    Sliding of Thin Filaments past Thick Filaments
  11. the molecular motor that generates force and movement in muscle via the Crossbridge
  12. Excitation Contraction Coupling
    • is the sequence of events that link the depolarization of the surface membrane
    • with tension development by the contractile machinery
  13. EC couple in skeletal vs cardiac: difference
    the sources of these action potentials and calcium pools
  14. Calcium Regulates Contraction:
    what is needed to keep myosin crossbridges cycling along actin filament?
    sufficient ATP and proximity to an available actin binding site.

    • •Striated muscle contraction is regulated by calcium via the thin filament proteins,
    • troponin and tropomyosin.
  15. how does Ca2+ regulate crossbridging of myosin with actin?
    by covering and uncovering the binding site of myosin on actin
  16. Release & Uptake of Calcium: unique mechanism that applies only to
    Skeletal Muscle
    DHP -ryanodine receptor and its opening from AP propagating on T-tubule 

    ATP-depending Ca2+ channel on SR
  17. True or false: 

    Events at the Neuromuscular Junction: cell to cell connection
  18. What happens between the action potential and contraction?
    Latent period, which is the time it take for Ca2+ to move around and start acting
  19. what helps transmit AP accross ms in the muscle bundle?
    Sarcoplasmic Reticulum / Transverse Tubules / Myofibrils
  20. which receptor triggers Calcium Release from the SR?
    DHP-ryanodine receptor
  21. what is the difference between heart's DHP receptor vs. ms?
    in the muscle, DHP receptor is physically opened by AP whereas heart DHP receptor is opened upon Ca2+
  22. Skeletal EC Coupling: Sequence of Events
    •Action potential generated at the neuromuscular junction is propagated along the sarcolemma.

    •T-tubular depolarization.

    •Signal transduction across the T-SR junction.

    –Via DHP / Ryanodine Receptor complex signaling mechanism.

    •Calcium release from the SR.

    •Calcium binding to TnC.

    •Crossbridge cycling and contraction.

    • •Calcium
    • resequestration by longitudinal SR.

  23. 100% of the calcium that binds to TnC in skeletal muscle is derived from...
    SR not extracellular space.
  24. True or False

    calcium that binds to TnC in skeletal muscle is come from extracellular space and SR
  25. force vs. time at a constant length.
  26. length vs. time at a constant force
  27. force, length & time all change
  28. Isotonic Twitches with different load (light, intermediate and heavy): velocity
    Light > intermediate > heavy
  29. lengthening contraction
    when load becomes too heavy, ms is lengthened and contract at the same time
  30. land from a jump produce (force? and type of contraction)
    highest force 

    Lengthening contraction
  31. Tetanic force is larger than twitch force because...
    the calcium is released faster than its re-uptake --> more available Ca2+ within the ms to activate contraction
  32. Muscle length and force: Length-Tension curve
    there is a normal working range where maximal tension is obtained

    inc in length inc in force. up to a point then the force dec in the presence of inc in ms length
  33. cardiac vs skeletal ms: which one has longer working range?
  34. source of energy in skeletal ms. which one is the most important source or give instant energy to ms?
    creatinine, glucolysis and oxidative phosphorylation

    Creatinine is the most important
  35. how does ms fatigue happen?
    deplete ATP or intracellular [Ca2+]
  36. Types of skeletal ms:
    • slow-oxidative
    • fast-oxidative 
    • Fast glycolytic
  37. Fiber type: rate of fatigue
    Slow-oxidative > fast-oxidative > fast glycolytic
  38. Fiber type: Diameter
    Fast-glycolytic > Fast-oxidative > Slow-oxidative
  39. Fiber type: myoglobin type
    • Red: Fast and slow-oxidative
    • White: fast-glycolytic (fewer mitochondria and myoglobin)
  40. Differences in the Development of Fatigue in the Three Skeletal Muscle Fiber Types
    Slow-oxidative fiber > Fast-oxidative fiber > Fast glycolytic fiber
  41. Force in skeletal ms is modulated by. Compared with cardiac modulation?
    recruiting or derecruiting motor units in skeletal muscle.

    change in Ca2+ concentration in cardiac ms.
  42. Motor unit in skeletal vs cardiac ms
    • Skeletal: single or multiple unit 
    • Cardiac: no motor unit
  43. Factors determining ms tension
    • 1. tension developed by each fiber
    • a. AP frequency
    • b. Fiber length
    • c. Fiber diameter
    • d. Fatigue
    • 2. number of active fibers
    • a. # of fiber per motor unit
    • b. # of active motor unit
  44. “Aerobic exercise” improves
    endurance via increased mitochondria & oxidative fibers.
  45. “Strength training” improves
    short-term power via increased glycolytic fibers & diameter.
  46. exercise ms leads to
    hypertrophy & alters ATP production capacity
  47. True or False

    exercise will increase # of ms fiber
  48. When does skeletal muscle become fatigue, energetically?
    •Skeletal muscle can fatigue when ATP generation can’t meet the metabolic demand of the muscle.
  49. True or False

    The rate of ATP production and use is not related to fiber type
  50. Skeletal muscle force is modulated by...
    recruting or de-recruiting motor units
  51. True or false:

    Motor units contains many different types of muscle
  52. True or False

    In motor units, fiber type and metabolic efficient is fixed and constant since birth
Card Set
Physiology of skeletal ms
Skeletal ms physiology