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Muscular System. Chp. 6. The Muscular System is very complex:. Figure 6.2. Muscle Function : Produce Movement or Generate Tension. Principle function - produce movement or generate tension Contraction : shorten distances between bones Skeletal muscles function to move bones

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muscle function produce movement or generate tension
Muscle Function: Produce Movement or Generate Tension
  • Principle function - produce movement or generate tension
  • Contraction: shorten distances between bones
  • Skeletal muscles function to move bones
  • Two major types muscle groups:

Synergistic muscles: groups work together

Antagonistic muscles: groups oppose each other

muscle structure
Muscle Structure:
  • Fascicles = bundles of muscle cells surrounded by sheath (connective tissue)
  • Muscle fibers= few doz.- 1,000’s muscle cells

Connective tissue surrounding

entire muscle, collectively, these connective tissues form tendons.

Figure 6.3

skeletal muscle contractile unit
Skeletal Muscle Contractile Unit:
  • Single muscle cell contains many myofibrils:
      • ea myofibril is composed of sacromeres
      • actin filaments
      • myosin filaments
      • z-lines
skeletal muscle contractile unit6
Skeletal Muscle Contractile Unit:
  • Sarcomere - segment of single myofibril from one Z-line to the next Z-line
  • Actin - protein w/tropomyosin binding sites
  • Myosin - thick filament w/ myosin heads
  • Z Lines - attachment points for sarcomeres
    • Actin filaments linked with z-line
    • Myosin filaments located w/in scaromeres
nerve activation of individual muscle cells
Nerve Activation of Individual Muscle Cells:
  • Acetylcholine released from motor neuron at neuromuscular junction
  • Electrical impulse transmitted along T tubules
  • Calcium released from sarcoplasmic reticulum
calcium initiates the sliding filament mechanism
Calcium Initiates the Sliding Filament Mechanism
  • Thick filaments: myosin
  • Thin filaments: strands of actin molecules
  • Contraction = formation of cross bridges between thin & thick filaments
mechanism of muscle contraction
Mechanism of Muscle Contraction:
  • Calcium released from sarcoplasmic reticulum
  • Calcium binds to troponin
  • Troponin-tropomysin complex shifts position
  • Myosin binding site exposed
  • Myosin heads form cross-bridges with actin
  • Actin filaments pulled toward center of sarcomere
muscle relaxation
Muscle Relaxation
  • Nerve activation ends, contraction ends
  • Calcium pumped back into sarcoplasmic reticulum
  • Calcium removed from troponin
  • Myosin-binding site covered
  • No calcium = no cross-bridges
energy required for muscle activity
Energy Required for Muscle Activity
  • Principle source of energy: ATP
  • ATP replenished by variety of means
    • Creatine phosphate
    • Stored glycogen
    • Aerobic metabolism of glucose, fatty acids, and other high-energy molecules
activity of muscles can vary
Activity of Muscles Can Vary
  • Isotonic contractions: muscle shortens, movement occurs
  • Isometric contractions: muscle doesn’t shorten, no movement
  • Degree of nerve activation influences force
  • Terms to know:
    • Motor unit
    • Muscle tension
    • All-or-none principle
    • Muscle tone
muscle contraction myogram
Muscle Contraction: Myogram
  • Latent period
  • Contraction
  • Relaxation
  • Summation vs. tetanus

Figure 6.10

muscle activity
Muscle Activity:

Slow Twitch vs. Fast Twitch Fibers

  • Slow twitch muscles: endurance, long duration contraction, contains myoglobin
    • E.g. Jogging, swimming, biking
  • Fast twitch: strength, white muscle, short duration contraction
    • E.g. Sprinting, weight lifting, tennis
exercise training
Exercise Training:
  • Strength training
    • Resistance training
      • Short, intense
      • Builds more fast-twitch myofibrils
  • Aerobic training
    • Builds endurance
    • Increases blood supply to muscle cells
      • Target heart rate at least 20 minutes, three times a week
features of cardiac smooth muscles
Features of Cardiac & Smooth Muscles:
  • Activation of cardiac and smooth muscles
    • Involuntary
    • Specialized adaptations in each
  • Speed and sustainability of contractions

3. Arrangement of myosin and actin filaments

diseases and disorders of the muscular system
Diseases and Disorders of the Muscular System
  • Muscular dystrophy
  • Tetanus
  • Muscle cramps
  • Pulled muscles
  • Fasciitis
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