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Ch09 c.muscles

Jun 27, 2015

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  • 1. HumanAnatomy& PhysiologySEVENTH EDITIONElaine N. MariebKatja HoehnCopyright 2006 Pearson Education, Inc., publishing as Benjamin CummingsPowerPoint Lecture Slidesprepared by Vince Austin,Bluegrass Technicaland Community CollegeC H A P T E R9Muscles andMuscle TissueP A R T C

2. Muscle Tone Muscle tone: Is the constant, slightly contracted state of allmuscles, which does not produce activemovements Keeps the muscles firm, healthy, and ready torespond to stimulus Spinal reflexes account for muscle tone by: Activating one motor unit and then another Responding to activation of stretch receptors inmuscles and tendonsCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 3. Isotonic Contractions In isotonic contractions, the muscle changes inlength (decreasing the angle of the joint) andmoves the load The two types of isotonic contractions areconcentric and eccentric Concentric contractions the muscle shortens anddoes work Eccentric contractions the muscle contracts as itlengthensCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 4. Isotonic ContractionsCopyright 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 9.19a 5. Isometric Contractions Tension increases to the muscles capacity, but themuscle neither shortens nor lengthens Occurs if the load is greater than the tension themuscle is able to developCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6. Isometric ContractionsCopyright 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 9.19b 7. Muscle Metabolism: Energy for Contraction ATP is the only source used directly for contractileactivity As soon as available stores of ATP are hydrolyzed(4-6 seconds), they are regenerated by: The interaction of ADP with creatine phosphate(CP) Anaerobic glycolysis Aerobic respirationPLAY InterActive Physiology :Muscle Metabolism, pages 3-15Copyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 8. Muscle Metabolism: Energy for ContractionCopyright 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 9.20 9. Muscle Metabolism: Anaerobic Glycolysis When muscle contractile activity reaches 70% ofmaximum: Bulging muscles compress blood vessels Oxygen delivery is impaired Pyruvic acid is converted into lactic acidCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 10. Muscle Metabolism: Anaerobic Glycolysis The lactic acid: Diffuses into the bloodstream Is picked up and used as fuel by the liver, kidneys,and heart Is converted back into pyruvic acid by the liverCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 11. Muscle Fatigue Muscle fatigue the muscle is in a state ofphysiological inability to contract Muscle fatigue occurs when: ATP production fails to keep pace with ATP use There is a relative deficit of ATP, causingcontractures Lactic acid accumulates in the muscle Ionic imbalances are presentCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 12. Muscle Fatigue Intense exercise produces rapid muscle fatigue(with rapid recovery) Na+-K+ pumps cannot restore ionic balancesquickly enough Low-intensity exercise produces slow-developingfatigue SR is damaged and Ca2+ regulation is disruptedCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 13. Oxygen Debt Vigorous exercise causes dramatic changes inmuscle chemistry For a muscle to return to a resting state: Oxygen reserves must be replenished Lactic acid must be converted to pyruvic acid Glycogen stores must be replaced ATP and CP reserves must be resynthesizedCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 14. Oxygen Debt Oxygen debt the extra amount of O2 needed forthe above restorative processesCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 15. Heat Production During Muscle Activity Only 40% of the energy released in muscle activityis useful as work The remaining 60% is given off as heat Dangerous heat levels are prevented by radiationof heat from the skin and sweatingCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 16. Force of Muscle Contraction The force of contraction is affected by: The number of muscle fibers contracting themore motor fibers in a muscle, the stronger thecontraction The relative size of the muscle the bulkier themuscle, the greater its strength Degree of muscle stretch muscles contractstrongest when muscle fibers are 80-120% of theirnormal resting lengthCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 17. Force of Muscle ContractionCopyright 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 9.21ac 18. Length Tension RelationshipsCopyright 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 9.22 19. Copyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 9.2 20. Muscle Fiber Type: Functional Characteristics Speed of contraction determined by speed inwhich ATPases split ATP The two types of fibers are slow and fast ATP-forming pathways Oxidative fibers use aerobic pathways Glycolytic fibers use anaerobic glycolysis These two criteria define three categories slowoxidative fibers, fast oxidative fibers, and fastglycolytic fibersPLAY InterActive Physiology :Muscle Metabolism, pages 16-22Copyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 21. Muscle Fiber Type: Speed of Contraction Slow oxidative fibers contract slowly, have slowacting myosin ATPases, and are fatigue resistant Fast oxidative fibers contract quickly, have fastmyosin ATPases, and have moderate resistance tofatigue Fast glycolytic fibers contract quickly, have fastmyosin ATPases, and are easily fatiguedPLAY InterActive Physiology :Muscle Metabolism, pages 24-29Copyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 22. Load and ContractionCopyright 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 9.23 23. Effects of Aerobic Exercise Aerobic exercise results in an increase of: Muscle capillaries Number of mitochondria Myoglobin synthesisCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 24. Effects of Resistance Exercise Resistance exercise (typically anaerobic) results in: Muscle hypertrophy Increased mitochondria, myofilaments, andglycogen storesCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 25. The Overload Principle Forcing a muscle to work promotes increasedmuscular strength Muscles adapt to increased demands Muscles must be overloaded to produce furthergainsCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 26. Smooth Muscle Composed of spindle-shaped fibers with adiameter of 2-10 m and lengths of severalhundred m Lack the coarse connective tissue sheaths ofskeletal muscle, but have fine endomysium Organized into two layers (longitudinal andcircular) of closely apposed fibersCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 27. Smooth Muscle Found in walls of hollow organs (except the heart) Have essentially the same contractile mechanismsas skeletal muscleCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 28. Smooth MuscleCopyright 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 9.24 29. Peristalsis When the longitudinal layer contracts, the organdilates and contracts When the circular layer contracts, the organelongates Peristalsis alternating contractions andrelaxations of smooth muscles that mix andsqueeze substances through the lumen of holloworgansCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 30. Innervation of Smooth Muscle Smooth muscle lacks neuromuscular junctions Innervating nerves have bulbous swellings calledvaricosities Varicosities release neurotransmitters into widesynaptic clefts called diffuse junctionsCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 31. Innervation of Smooth MuscleCopyright 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 9.25 32. Microscopic Anatomy of Smooth Muscle SR is less developed than in skeletal muscle andlacks a specific pattern T tubules are absent Plasma membranes have pouchlike infoldings calledcaveoliCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 33. Microscopic Anatomy of Smooth Muscle Ca2+ is sequestered in the extracellular space nearthe caveoli, allowing rapid influx when channelsare opened There are no visible striations and no sarcomeres Thin and thick filaments are presentCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 34. Proportion and Organization of Myofilamentsin Smooth Muscle Ratio of thick to thin filaments is much lower thanin skeletal muscle Thick filaments have heads along their entire length There is no troponin complexCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 35. Proportion and Organization of Myofilamentsin Smooth Muscle Thick and thin filaments are arranged diagonally, causingsmooth muscle to contract in a corkscrew manner Noncontractile intermediate filament bundles attach todense bodies (analogous to Z discs) at regular intervalsCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 36. Proportion and Organization of Myofilamentsin Smooth MuscleCopyright 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 9.26 37. Contraction of Smooth Muscle Whole sheets of smooth muscle exhibit slow,synchronized contraction They contract in unison, reflecting their electricalcoupling with gap junctions Action potentials are transmitted from cell to cellCopyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings 38. Contraction of Smooth Muscle Some smooth muscle cells: Act as pacemakers and set the contractile pace forwhole sheets of muscle Are self

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