Myology the study of muscles
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Myology, the study of muscles. Three different types of muscle. Skeletal Move skeleton Striated Voluntary Cardiac Striated Involuntary Autorhythmicity Smooth Not striated Usually involuntary Some autorhythmicity. Major functions of muscle. Regulating movement

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Three different types of muscle
Three different types of muscle

  • Skeletal

    • Move skeleton

    • Striated

    • Voluntary

  • Cardiac

    • Striated

    • Involuntary

    • Autorhythmicity

  • Smooth

    • Not striated

    • Usually involuntary

    • Some autorhythmicity


Major functions of muscle
Major functions of muscle

  • Regulating movement

  • Stabilizing body positions

  • Movement of materials around body

  • Regulating body temperature

  • Properties:

    • Excitability

    • Contractility

    • Extensibility

    • Elasticity


Organization of skeletal muscle
Organization of skeletal muscle

  • Superficial fascia separate muscle from skin

  • Deep fascia separate groups of muscles from each other

    • Epimysium-entire muscle

    • Perimysium-fascicle

    • Endomysium- individual muscle fibers



Sarco refers to muscle
“Sarco” refers to muscle

  • Sarcolemma-excitable membrane (T tubules)

  • Sarcoplasm- glycogen, myoglobin, myofibrils

  • Sarcoplasmic reticulum

    • Stores calcium

    • Triad- regulates calcium movement



Muscle proteins
Muscle proteins

  • Contractile proteins

    • Actin, myosin

  • Regulatory proteins

    • Tropomyosin, troponin

  • Structural proteins

    • Titin, myomesin, dystrophin






Many drugs affect muscle function through effects on nmj
Many drugs affect muscle function through effects on NMJ

  • Botulism toxin

    • Prevents release of acetylcholine

  • Curare

    • Blocks ACh receptors

  • Tetanus toxin

    • Blocks inhibitory neurons


Importance of ach function
Importance of Ach function

Botox treatment

Myasthenia gravis


Muscle tone
Muscle tone

  • Subset of muscle fibers produces continuous contraction

    • Stabilizes but does not contribute to movement in skeletal muscles

      • Too much: rigidity, too little- spasticity

      • Electrolyte imbalance

  • Important in smooth muscle function


Types of muscle fibers
Types of muscle fibers

  • Red and white

  • Slow oxidative fibers

    • Lots of mitochondria, myoglobin

    • Good blood supply (oxygen)

    • Postural muscles

  • Endurance


More muscle fibers p 277
More muscle fibers (p. 277)

  • Fast glycolytic fibers

    • Largest; most powerful contractions

    • Poor blood supply (“white” fibers”)

    • Lots in arm muscles

    • Fatigue easily

  • Fast oxidative-glycolytic fibers

    • Intermediate

    • Use ATP faster than slow fibers

    • Lots in leg muscles



Smooth muscle
Smooth muscle

  • Single-unit

    • Most common

    • Autorhythmic

    • Stimulation of one fiber spreads to another

  • Multiple-unit

    • Larger arteries, lungs, etc.

    • Only stimulated fiber is affected


Unique features of smooth muscle compared to skeletal muscle
Unique features of smooth musclecompared to skeletal muscle:

  • Smooth muscle has longer, slower contraction

  • Calcium regulation method is different

  • Can stretch and still be able to contract

  • Best at regeneration

  • See p. 281


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