Active SubsystemEX2

Active SubsystemEX2 - Skeletal Muscle - Striated Axial...

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Skeletal Muscle - Striated
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Axial Muscles (skeleton) - muscles (bones) of the head, neck, trunk Appendicular Muscles (skeleton) - muscles (bones) of the limbs
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Scapula Bellies Radius Insertion Humerus Ulna Insertion Origins Origins Triceps brachii Extensors Long head Lateral head Flexors Biceps brachii Brachialis 1 Muscle - 2 Attachments Pulling Force on attachments
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SKELETAL MUSCLE Most abundant tissue in body Forms about 40-50% of adult mass The ultimate force generator in the body Movement (forces not equal) Stability (forces equal) Metabolic processes, major heat, waste Expression Voluntary muscle vs. cardiac & smooth
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SKELETAL MUSCLE PROPERTIES Extensibility (stretch) and Elasticity (recoil): enable the muscle to be stretched, and return to normal length (protective mechanism) Tendons are continuations of muscle’s connective tissue, also possess these properties Contractility: is the ability to shorten and produce tension Conductivity: conduction of electrical excitation (via muscle stimulation) along membrane initiating contraction Excitability (irritability): stimulation produces electrical change
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Groups of Muscles Muscles typically act in unison – not  individually Fascia Sheet of fibrous tissue (collagen  and some elastin) Compartmentalizes groups of  muscles
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Skeletal muscle Perimysium Epimysium Endomysium Nerve Blood vessels Muscle fascicle (bundle of fibers) Muscle Fiber (cell) Tendon Deep fascia Individual Muscle Organization
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Connective Tissue of Muscle The Fascia a) Endomysium surrounds each muscle fiber or cell b) Perimysium binds muscle fascicles (fiber bundles) c) Epimysium surrounds whole muscle Connective tissues (collagen) Are slightly elastic, resistive force when stretched Purpose of Fascia?
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This is 1 muscle fiber (cell) with many myofibrils Read sections 10.5-10.13 Muscle fibers consist of myofibrils held together by sarcolemma (cell membrane), which propogate nerve impulses.
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sarcolemma has transverse tubules that carry impulse from outer cell to inner cell electrical activity causes release of Ca++ that activates the contraction process myofibrils are composed of parallel protein microfilaments called myofilaments which create alternating dark & light bands that give muscle fiber their striated appearance myofibrils connect to tendon via endomysium 2 types of myofilaments (proteins) are actin and myosin and these interact through cross- bridges
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Muscle Fiber Architecture Force a muscle can exert is proportional to its physiological cross section (more contractile elements) Generally, the thicker the muscle the greater the force potential Angle of orientation (pennation angle ) between muscle fibers and tendon also determines force If muscle fibers attach parallel to tendon (0º), essentially all force generated is transmitted
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A pennate muscle of the same thickness as a longitudinal muscle can exert greater force
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This note was uploaded on 11/10/2011 for the course KNH 244L taught by Professor Omolewu during the Spring '10 term at Miami University.

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Active SubsystemEX2 - Skeletal Muscle - Striated Axial...

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