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The Muscular System

The Muscular System. Muscles Facts. Are there more muscles or bones? Muscles (around 640) Each lb of muscle burns 75-100 calories a day just by being. Muscles Facts (cont.). Approximately 40% of your body weight is muscle Largest muscle = gluteus maximus.

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The Muscular System

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  1. The Muscular System

  2. Muscles Facts • Are there more muscles or bones? • Muscles (around 640) • Each lb of muscle burns 75-100 calories a day just by being

  3. Muscles Facts (cont.) • Approximately 40% of your body weight is muscle • Largest muscle = gluteus maximus

  4. Muscles Facts (cont.) • Smiling uses 17 muscles • Frowning uses 43 muscles

  5. The Role of Muscle • muscle tissue contracts (shortens) and causes movement

  6. Where are muscles? • attached to your skeleton(skeletal) • in your heart(cardiac) • in your stomach and intestines(smooth) • called the MUSCULAR SYSTEM

  7. Human Muscles

  8. Muscle Basics • Muscles are made of bundles of protein fibers

  9. Muscle Basics • The two main fibers are actin (thin protein) and myosin (thick protein)

  10. Muscle Basics • Remember: what moves muscles? • Motor neurons • Acetylcholine- a neurotransmitter released & moves across synapse and contracts muscle.

  11. Types of Muscle 1. Skeletal muscle • attached to bones of skeleton • Voluntary (we control them)  most of the meat we eat is this tissue

  12. Skeletal Muscle Continued: • Microscope: • Alternating light & dark bands • Striations • Many nuclei

  13. Types of Muscle (cont.) 2. Smooth muscle • Found in hollow structures: stomach, blood vessels & intestines • involuntary

  14. Smooth Muscle Cont’d: • Spindle-shaped • One nucleus • Not striated

  15. Types of Muscle (cont) 3. Cardiac muscle • found only in heart • not connected to bone • involuntary (we don’t control)

  16. Cardiac Muscle Cont’d: • Striated like skeletal muscle • One nucleus (may have 2) • Involuntary like smooth muscle

  17. Muscle Contractions • Muscles shorten (they contract) • They are connected to bones by tendons (achilles, forearm)

  18. Muscles Work in Pairs • When one muscle contracts, the opposite one must relax • quadriceps / hamstrings • biceps / triceps • tibialis / gastrocnemius

  19. Nerves Activate Muscles • Muscles contract when sent a signal from the nervous system • Signals may vary • more muscle cells/fibers result in more force generated

  20. Muscle Fatigue • Results from oxygen debt • Lactic acid builds up and muscle can’t contract effectively • Recovery period “flushes out” lactic acid and delivers oxygen

  21. MuscularSystem Problems • Strain: tearing of fibers • Cramp: not enough oxygen, overuse • Muscular Dystrophy: nerve messages to muscles are blocked

  22. Steroids • Increase rate of muscle growth • Stop bone growth • Side Effects: Heart attack, shriveled testes, etc.

  23. Exercise & Muscles • When muscles are not used the cells become smaller & weaker • Two main types of exercise: aerobic & anaerobic

  24. Aerobic Exercise • Oxygen used rapidly by muscles • Uses slow twitch muscle • Glucose broken down • Ex: swimming & jogging

  25. Anaerobic Exercise • High intensity • Uses fast twitch muscle • Glucose converted to lactic acid (muscle burn) • Ex: sprinting & weight lifting

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