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Energy for skeletal muscle contraction

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Presentation on theme: "Energy for skeletal muscle contraction"— Presentation transcript:

1 Energy for skeletal muscle contraction
ATP sources The many causes of muscle fatigue Classification of skeletal muscle fiber types

2 ATP and muscle contraction
Need ATP for Cross-bridge formation, power stroke (myosin ATPase) Ca++ transport to SR (Ca++ ATPase) Na+/K+ transport across sarcolemma (Na+/K+ ATPase)

3 Sources of ATP ATP pool Phosphocreatine.
At rest, ATP phosphorylates creatine. During exercise, creatine kinase (creatine phosphokinase) moves phosphate from phosphocreatine to ATP

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5 Sources of ATP Glucose (glycolysis) to pyruvate citric acid cycle  oxidative phosphorylation (about 30 ATP per glucose molecules) Anaerobic glycolysis: glucose  lactic acid (2 ATP per glucose molecule)

6 Sources of ATP Beta oxidation of fatty acids. Fatty acids are converted to acetyl CoA citric acid cycle in the mitochondria, need oxygen Slow During light exercise

7 Sources of ATP glucose catabolism during heavy exercise
carbo loading builds up glycogen stores Protein catabolism during starvation

8 Fatigue Muscle is no longer able to generate sustained expected power output A variety of contributing factors depends on the degree of muscle activity

9 Fatigue: contributing factors
Intensity of muscle activity Duration of muscle activity Aerobic/anaerobic metabolism Muscle composition Fitness level Ions Nutrients Neurotransmitter

10 Fatigue during extended submaximal exertion
Not ATP shortage Glycogen depletion may affect Ca++ release from SR

11 Fatigue during short duration maximal exertion
Lots of inorganic phosphate from ATP hydrolysis  may slow P release from myosin:ADP:Pi  slows power stroke Acidosis may inhibit some enzymes

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13 More factors for muscle fatigue
K+ : intracellular K+ lowered during repetitive action potentials affects Ca++ release channels on SR membrane Acetyl choline depletion at the myoneural junction low end-plate potential (disease)

14 More factors for muscle fatigue
CNS: Subjective feelings preceding physiological fatigue Acidosis may influence perception of fatigue


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