C H A P T E R

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C H A P T E R
Muscle Physiology
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Chapter Outline
?Skeletal muscle macrostructure and microstructure
?Sliding-filament theory of muscular contraction
?Fiber types
?Types of muscle action
?Force production
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Three Types of Connective TissueEpimysium,
Perimysium, and Endomysium
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A Motor Unit
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Sectional View of a Muscle Fiber
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Detailed View of Myosin and Actin Protein
Filaments in Muscle
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The discharge of an action potential from a motor
nerve signals the release of calcium from the
sarcoplasmic reticulum into the myofibril,
causing tension development in muscle.
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Contraction of a Myofibril Stretched Muscle
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Contraction of a Myofibril Partially Contracted
Muscle
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Contraction of a Myofibril Completely
Contracted Muscle
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Calcium and ATP are necessary for myosin
cross-bridge cycling with actin filaments.
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Type II, or fast-twitch, muscle fibers are
capable of developing higher forces than Type I,
or slow-twitch, muscle fibersespecially at
higher velocities of muscle action.
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The number of cross-bridges that are attached to
actin filaments at any instant in time dictates
the force production of a muscle.
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Force-Velocity Curve for Eccentric and
Concentric Actions
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Three Arrangements of Muscle Fibers
Fibers parallel to tendon
Bipennate muscle
Unipennate muscle
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Many factors may affect rate of cross-bridge
cycling and thus force, including neural
activation, calcium concentration, myosin ATPase
activity, preloading, prestretch, muscle fiber
type and ultrastructure, fatigue through a
variety of mechanisms, and number of contractile
components (myosin and actin) in parallel.