The Muscular System

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The Muscular System
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Muscle Tissues

• Cardiac
• Involuntary striated muscle
• Found only in heart
• Smooth
• Lines blood vessels, digestive organs, urinary
  system, and parts of respiratory system, pupils
  of eyes
• Involuntary non-striated muscle
• Skeletal
• Voluntary striated muscle
• Attached to bones for movement

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Functions of Skeletal Muscle

• Produce Movement
• Contractions pull on tendons and move bones
• Maintain posture and body position
• Continuous contractions maintain posture
• Support/protect soft tissues
• Abdominal wall
• Floor of pelvic cavity
• Guard entrances and exits
• Voluntary control of swallowing, defecation, and
  urination
• Maintain body temp
• Some energy from contractions lost as heat

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Gross Anatomy of Skeletal Muscle

• Each cell is called a muscle fiber
• Connective
• Epimysium collagen fibers surrounding entire
  muscle
• Perimysium divide skeletal muscles into bundles
  of fibers (fascicles)
• Endomysium surrounds fiber
• Tendons connect skeletal muscle to periosteum
  of bones

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Microanatomy of Skeletal Muscle

• Sarcolemma cell membrane
• Sarcoplasm cytoplasm
• Myofibrils bundles of myofilaments
• Thin filaments actin proteins
• Thick filaments myosin proteins
• Sarcoplasmic reticulum smooth ER (stores Ca)
• Sarcomeres repeating units of myofilaments

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http//legacy.owensboro.kctcs.edu/gcaplan/anat/not
es/api20notes20j2020muscle20contraction.htm
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Muscle Fiber Contraction
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Muscle Tone

• Tone resting tension
• Stabilizes the position of your joints
• Any skeletal muscle not stimulated on a regular
  basis will atrophy fibers become smaller and
  weaker
• Initially atrophy is reversible
• Extreme atrophy is permanent

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Energetics of Muscle Activity

• Sources of ATP
• Aerobic Metabolism (Krebs ? Oxidative
  Phosphorylation)
• Provides 30 of ATP needed during peak exertion
• Waste products?Carbon dioxide and water vapor
• Anaerobic Metabolism (glycolysis)
• Waste products?Lactic acid builds up
• Ineffective
• Muscle Fatigue no contraction despite
  stimulation
• Lack of ATP or lactic acid build up

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Muscle Performance

• Force and endurance depends on
• Types of muscle fibers
• Fast Twitch (white)
• Powerful contractions
• Fatigue rapidly (few mitochondria)
• Slow Twitch (red)
• Extended contraction (many mitochondria)
• Extensive capillary network
• Myoglobin binds O2
• Physical conditioning ( increase power and
  endurance)