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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Myology, the study of muscles

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Myology the study of muscles

Myology, the study of muscles


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


Organization of a muscle fiber

Organization of a muscle fiber


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


Organization of the sarcomere

Organization of the sarcomere


Muscle proteins

Muscle proteins

  • Contractile proteins

    • Actin, myosin

  • Regulatory proteins

    • Tropomyosin, troponin

  • Structural proteins

    • Titin, myomesin, dystrophin


Sliding filament model

Sliding filament model


The sliding filament mechanism

The sliding filament mechanism


Roles of actin and myosin

Roles of actin and myosin


The neuromuscular junction

The neuromuscular junction


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


Cardiac muscle is specialized in the heart

Cardiac muscle is specialized in the heart


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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