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Muscle Physiology

Muscle Physiology. Chapter 8. ehow.com. Objectives. Know the functions and anatomy of a muscle Understand what causes a muscle contraction and the sliding filament mechanism Know the two types of muscular contractions Be able to interpret a myogram

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Muscle Physiology

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  1. Muscle Physiology Chapter 8 ehow.com

  2. Objectives • Know the functions and anatomy of a muscle • Understand what causes a muscle contraction and the sliding filament mechanism • Know the two types of muscular contractions • Be able to interpret a myogram • Understand how the different muscle fibers operate creatingacomic.com

  3. Functions • Produces movement • Maintains posture • Stabilizes joints • Generates heat home-gym-fitness-equipment.co.uk

  4. Structure • Macro to micro • Epimysium • Fascicles • Wrapped by perimysium • Muscle fibers (cells) • Wrapped by endomysium • Myofibrils • Contractile element training.seer.cancer.gov faculty.etsu.edu

  5. Microanatomy of Myofibril • Dark band • A band • Light band • I band • H zone • Z disc • Sarcomere • Titin • Largest protein in body • Stabilizes thick fillaments • Gives muscle elasticity http://legacy.owensboro.kctcs.edu/gcaplan/anat/images/Image286.gif

  6. The Sarcomere • Functional unit • Microfilaments • Actin • Troponin • Tropomyosin • Myosin • Heads contain two binding sites • Actin and ATPase scioly.org people.eku.edu

  7. Muscular Contraction • What needs to happen in order for a muscular contraction to begin?

  8. Sliding Filament Theory • Proposed by Hugh Huxley in 1954 • Mechanism by which sarcomeres contract • Involves formation of cross-bridges between actin and myosin • Thin filaments slide over thick filaments • Greater overlap between filaments

  9. Sliding Filament Mechanism • Calcium released from sarcoplasmic reticulum • Foot proteins stimulated by dihydropyridine receptors of T tubules • Calcium binds to troponin • Troponin–tropomysincomplex shifts position • Myosin binding site exposed • Myosin heads form cross-bridges with actin • Actin filaments pulled toward center of sarcomere

  10. Calcium Initiates the Sliding Filament Mechanism (cont.) Figure 6.7

  11. Role of ATP octc.kctcs.edu

  12. Muscle Relaxation • Nerve activation ends, contraction ends • Calcium pumped back into sarcoplasmic reticulum • Ca2+ - ATPase pump • Calcium removed from troponin • Myosin-binding site covered • No calcium = no cross-bridges

  13. Energy Required for Muscle Activity • Principle source of energy: ATP • ATP replenished by variety of means: • Creatine phosphate • Stored glycogen • Aerobic metabolism of glucose, fatty acids, and other high-energy molecules

  14. Activity of Muscles Can Vary • Isotonic contractions: muscle tension remains constant as muscle changes length • Concentric – muscle shortens • Eccentric – muscle stretched, but still contracting • Isometric contractions: muscle prevented from shortening, tension develops at constant muscle length • Degree of nerve activation influences force • Terms to know: • Motor unit • Muscle tension • All-or-none principle

  15. Muscle Contraction: Myogram • Latent period • Contraction • Relaxation • Summation vs. tetanus

  16. Types of Muscle Fibers Slow-twitch Fast-twitch Fast-oxidative (type IIa) Red fibers High myosin ATPase activity Fast-glycolytic (typeIIx) White fibers Fast twitch: strength, white muscle, short duration contraction: Sprinting, weight lifting • Slow oxidative (type I) • Red fibers • Low myosin ATPase activity • Slow twitch: endurance, long duration contraction : • Jogging, swimming, biking

  17. Features of Cardiac and Smooth Muscles • Activation of cardiac and smooth muscles: • Involuntary • Specialized adaptations in each • Speed and sustainability of contractions • Arrangement of myosin and actin filaments

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