Muscle Physiology
Types
of Muscle
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Skeletal
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Provides for body movement
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Smooth
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Provides for appropriate distribution
of blood flow during exercise
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Cardiac
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Provides appropriate distribution of
blood flow for body functions
Connective Tissue of Skeletal Muscle
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Epimysium
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Outer covering that is continuous with tendons
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Covers all 430 skeletal muscles in body
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Perimysium
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Outer covering for fasciculi (bundles of muscle fibers
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Endomysium
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Outer covering for each muscle fiber
The
Muscle Fiber
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Contains hundreds to thousands of
myofibrils
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Contain the apparatus to contract the
muscle fiber
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Apparatus include:
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Sarcoplasmic Reticulum
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Transvers Tubule – area of calcium
storage
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Longitudinal Tubule - roadway for
calcium transport to myofilaments
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Myofilaments
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Actin
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Myosin
- crossbridge
connection
Muscle
Contraction
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Process
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Signal from brain and/or spinal cord
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Signal moves along nerve to neuromuscular junction
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Ach in junction transports message to muscle
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Electrical activity in muscle signals calcium to be
released from area of transverse tubule
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Calcium moves through longitudinal tubule
The
Neuromuscular Junction
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Gap between the nerve ending and muscle fiber
Muscle
Contraction
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Process continues
6. Calcium binds to troponin
7. Tropomyosin (inhibitory protein) moves out of way to allow
myosin crossbridge to connnect to actin
8. Myosin crossbridge connects to actin
9. ATP is broken down and releases energy
10. Crossbridge moves actin inward causing shortening of
muscle fiber
11. Ratcheting effect continues until contraction is complete
Types
of Contraction
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Isometric
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Developing tension in the muscle
without a change in muscle length
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Isotonic
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Developing tension in the muscle with
a change in muscle length
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Concentric – shortening
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Eccentric – lengthening
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Isokinetic
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Developing tension in the muscle that
is met by an equal opposing resistance
Force
Production
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Dependent upon:
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Number of crossbridges connected to actin at
any instant in time
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Preloaded or unpreloaded state
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Eg. When lifting a barbell, isometric
contraction is needed to hold the weight (preloaded)
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Eg. When lifting with hydraulic or
isokinetic systems (unpreloaed)
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Cross-sectional area – size matters
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Velocity of shortening
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Less force production is possible the
faster the contraction
Force
Production
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Dependent upon:
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Angle of
pennation (arrangement of fibers)
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3 types
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Muscle fibers run parallel
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One set of muscle fibers are oblique to tendon
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Muscle fibers are aligned at oblique angle on both
sides of tendon
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Sarcomere Length
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Prestretching
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Can enhance force of a concentric contraction
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Due to elasticity and stretch-shortening phenomenon
Force
Production
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Dependent upon:
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Exercise-induced muscle damage
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Hard exercise can lead to DOMS
(delayed onset of muscle soreness)
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Occurs 24-48 hours after hard
exercise
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Most likely due to tearing of muscle
and connective tissue
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Age of muscle
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Sarcopenia – reduced muscle size and
strength
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Fiber Type
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Fast-twitch
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Slow-twitch