KINE 2031 Lecture Notes - Lecture 11: Phosphocreatine, Glycogen, Oxidative Phosphorylation
2 Jul 2018
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Muscle Physiology Summary
Introduction
-Muscles are specialized for contraction- develop tension, shorten, produce movement &
accomplish work
-Three types of muscle- skeletal, cardiac & smooth
-Two ways to categorize them:
1. Unstrained- smooth; straited- cardiac & skeletal
2. Voluntary- skeletal; involuntary- cardiac & smooth
Structure of Skeletal Muscles
-Skeletal muscles made of bundles of cylindrical muscle cells called muscle fibers, wrapped in
connective tissues
-Muscle fibres packed with myofibrils. Each myofibril packed with alternating thick & thin
filaments – leads to straited appearance of dark A bands & light I bands
-Thick filaments contain myosin. Cross-bridges made of myosin’s globular heads which bind
to thin filaments
-Thin filaments contain actin which bind & interact w/myosin cross-bridge to bring
contraction. In resting state, regulatory proteins troponin & tropomyosin lie across thin
filaments to prevent cross-bridge interaction
Molecular Basis of Skeletal Muscle Contraction
-Excitation of skeletal muscle by motor neurons brings contraction that results in thin
filaments sliding closer together b/t thick filaments
-Sliding filament mechanisms of muscle contraction occurs from release of Ca2+ from lateral
sacs of SR
-Calcium release occurs in response to spread of muscle fibre’s action potential into central
portions of fibre via T-tubule
-Released Ca2+ binds troponin-tropomyosin complex of thin filaments, repositioning them to
uncover actin’s cross-bridge binding sites
-Exposed actin binds to myosin crossbridge. Energy released from myosin heads stored from
ATP hydrolysis allows power stroke
-During power stroke, an activated cross bridge bends towards center of thick filaments
moving actin filaments inward
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Muscles are specialized for contraction- develop tension, shorten, produce movement & accomplish work. Three types of muscle- skeletal, cardiac & smooth. Two ways to categorize them: unstrained- smooth; straited- cardiac & skeletal, voluntary- skeletal; involuntary- cardiac & smooth. Skeletal muscles made of bundles of cylindrical muscle cells called muscle fibers, wrapped in connective tissues. Each myofibril packed with alternating thick & thin filaments leads to straited appearance of dark a bands & light i bands. Cross-bridges made of myosin"s globular heads which bind to thin filaments. Thin filaments contain actin which bind & interact w/myosin cross-bridge to bring contraction. In resting state, regulatory proteins troponin & tropomyosin lie across thin filaments to prevent cross-bridge interaction. Excitation of skeletal muscle by motor neurons brings contraction that results in thin filaments sliding closer together b/t thick filaments. Sliding filament mechanisms of muscle contraction occurs from release of ca2+ from lateral sacs of sr.
