Muscular System


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a general outline of the human muscular system as it relates to exercise

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Muscular System

  1. 1. Applied Exercise Physiology Section 5: Body Systems Topic 1: Muscular System Prepared by Mr. Cerny Niagara Wheatfield Senior High School
  2. 2. Types of Muscle <ul><li>Cardiac </li></ul><ul><ul><li>Heart </li></ul></ul><ul><li>Smooth </li></ul><ul><ul><li>Organ lining </li></ul></ul><ul><li>Skeletal </li></ul><ul><ul><li>Movement </li></ul></ul><ul><ul><li>40% of total body mass </li></ul></ul>
  3. 3. Types of Muscle (con’t) Cardiac Smooth Skeletal
  4. 4. Skeletal Muscle <ul><li>How many different muscles can there be? </li></ul>
  5. 5. Skeletal Muscle <ul><li>How many different muscles can there be? </li></ul><ul><li>~660 </li></ul>
  6. 6. Skeletal Muscle Structure <ul><li>Cylindrical fibers bunched together </li></ul>Cable wire c.s.
  7. 8. <ul><li>It is the number of muscle fibers packed into a given muscle cross-sectional area that determine overall force-generating capacity </li></ul>Macrostructure Skeletal muscle c.s. 40x
  8. 11. Microstructure <ul><li>Sarcomere: </li></ul><ul><li>basic functional unit of muscle </li></ul><ul><li>Striated (light & dark bands) </li></ul><ul><li>Contains ACTIN & MYOSIN filaments that are responsible for contraction </li></ul>
  9. 12. Actin & Myosin
  10. 13. Sliding-Filament Theory <ul><li>Using the list of “characters” below, create a storyboard showing the many different steps involved with the sliding-filament theory. Each step should contain a colored drawing (labeled if necessary) and a short explanation. </li></ul><ul><ul><li>“ Characters:” </li></ul></ul>Calcium (Ca ++ ) Troponin Tropomyosin ATPase ATP Myosin Actin
  11. 14. Misc. <ul><li>Role of ATPase: </li></ul><ul><ul><li>Enzyme that allows ATP on the myosin head to release energy (  ADP + P) so that it can form a cross bridge on actin </li></ul></ul><ul><ul><li>Needed again to detach </li></ul></ul><ul><li>Power Stroke: </li></ul><ul><ul><li>After myosin head attached and “pulls” on the actin </li></ul></ul><ul><li>What is rigor mortis? </li></ul><ul><ul><li>In relationship to the sliding-filament theory, explain how rigor mortis occurs. </li></ul></ul>
  12. 15. Where did the Ca ++ come from? <ul><li>Ca ++ is stored and released from the sarcoplasmic reticulum (SR) </li></ul><ul><li>SR is a network of tubules within the muscle fiber </li></ul>
  13. 16. Sarcoplasmic Reticulum
  14. 17. Nerves & Muscles <ul><li>An action potential (signal traveling along a neuron) causing contraction is termed Excitation-Contraction Coupling </li></ul>
  15. 18. Excitation-Contraction Coupling <ul><li>Action potential travels along neuron by the temporary changing of charges </li></ul><ul><li>Nerve impulse causes the release of acetylcholine (ACh). </li></ul><ul><li>ACh travels across neuromuscular junction, binding to muscle cell membrane. </li></ul><ul><li>ACh binding initiates an electrical impulse which travels across membrane and into T tubules. </li></ul><ul><li>Impulse stimulates release of Ca +2 from SR. </li></ul><ul><li>Ca +2 binds with t-t complex of the actin filaments, shifting it's position, exposing myosin binding sites. </li></ul><ul><li>Myosin binds to actin; Ca +2 presence also causes enzymatic actions of myosin to breakdown ATP into ADP + P + energy. </li></ul><ul><li>Energy of ATP degradation causes shape change of myosin head, pulling actin molecule toward center of sacromere. </li></ul><ul><li>After sliding, a new ATP binds to myosin, breaking the myosin-actin bond, releasing the myosin head. </li></ul><ul><li>If Ca +2 is still present, the process repeats itself until sacromere has shortened completely. </li></ul><ul><li>If a nerve impulse ceases, the Ca +2 is reabsorbed by the SR and the muscle relaxes. </li></ul>
  16. 19. Muscle Fatigue <ul><li>What is it? </li></ul><ul><ul><li>Decline in force-producing capabilities over time </li></ul></ul><ul><li>What’s the point? </li></ul><ul><li>Prevents exhausting of metabolic (energy-producing) reserve (like enzymes) </li></ul><ul><li>Limits the buildup of harmful products </li></ul><ul><li>Reduces the likelihood of damage to the contractile elements (ex.: sarcomeres) </li></ul>
  17. 20. Muscle Fatigue 1 <ul><li>What causes it? </li></ul><ul><li>1) Reduction in ATP </li></ul><ul><ul><li>Under high stress, ATP utilization reduced faster than ATP production </li></ul></ul><ul><li>2) Peripheral metabolic bi-products </li></ul><ul><ul><li>Lactic acid </li></ul></ul><ul><ul><li>H (and other free radicals) </li></ul></ul>
  18. 21. Muscle Fatigue <ul><li>3) Dehydration </li></ul><ul><ul><li>Increases temp = decreases contractile properties </li></ul></ul><ul><li>4) Decrease nerve signals/action potentials </li></ul><ul><li>5) Reduction of Ca </li></ul><ul><ul><li>“ leakage ” 1 </li></ul></ul><ul><ul><li>From decrease nerve connection </li></ul></ul>
  19. 22. Specificity of Muscle Fiber Recruitment <ul><li>Each activity will recruit different groups & different numbers of muscle fibers </li></ul><ul><li>Thus…in order to increase force production for a particular activity, you must train those specific muscle fibers used in that activity </li></ul>
  20. 23. Specificity of Muscle Fiber Recruitment <ul><li>What does this mean for training ? </li></ul><ul><ul><li>In order for optimum adaptation to occur during training, muscles should be trained in a manner similar to the way they are expected to perform during competition </li></ul></ul><ul><li>What does this mean for rehabilitation ? </li></ul><ul><ul><li>Return to work in a timely manner requires you to look at exactly what that worker will be doing </li></ul></ul>
  21. 24. Muscle Types <ul><li>Difference dependant on contraction time (rate of cross-bridge cycling) NOT amount of force produced </li></ul><ul><li>“Twitch”: response of skeletal muscle fiber to a single electrical stimulus </li></ul><ul><li>Muscle Types: </li></ul><ul><ul><li>Slow twitch (Type I) </li></ul></ul><ul><ul><li>Fast twitch (Type II) </li></ul></ul>
  22. 25. Muscle Types nonoxidative Few Sprinting /bursts No Few Fast Same (slightly more) Fast twitch (II) Oxidative Many Endurance Yes Many Slow Same (slightly less) Slow twitch (I) Oxidative / nonoxidative # capillaries Activity Resistance to fatigue # mit. Speed Force
  23. 26. Muscle Injury <ul><li>DOMS </li></ul><ul><ul><li>“ Delayed onset muscle soreness” </li></ul></ul><ul><ul><li>Damage to sarcomere properties </li></ul></ul><ul><ul><ul><li>Actual protein molecules in sarcomere </li></ul></ul></ul><ul><ul><ul><ul><li>Titin </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Nebulin </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Costamere </li></ul></ul></ul></ul><ul><ul><li>Exacerbated by dehydration </li></ul></ul><ul><ul><li>Recovering faster with steroids </li></ul></ul>
  24. 28. Muscle Strength <ul><li>“ Bigger” muscles: </li></ul><ul><ul><li>Usually NOT increase in muscle cells (hyperplasia) </li></ul></ul><ul><ul><li>Usually an increase in existing tissue size (hypertrophy) </li></ul></ul><ul><li>Factors contributing: </li></ul><ul><li>Genetics </li></ul><ul><li>Exercise </li></ul><ul><li>Nutrition </li></ul><ul><li>Endocrine </li></ul><ul><li>Environmental </li></ul><ul><li>Nervous </li></ul>