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Energy for Muscle Contraction:

Energy for Muscle Contraction:. Initially, muscles use stored ATP for energy Bonds of ATP are broken to release energy Only 4-6 seconds worth of ATP is stored by muscles After this initial time, other pathways must be utilized to produce ATP:. 1. Direct Phosphorylation of ADP by CP.

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Energy for Muscle Contraction:

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  1. Energy for Muscle Contraction: • Initially, muscles use stored ATP for energy • Bonds of ATP are broken to release energy • Only 4-6 seconds worth of ATP is stored by muscles • After this initial time, other pathways must be utilized to produce ATP:

  2. 1. Direct Phosphorylation of ADP by CP Muscle cells contain creatine phosphate (CP) • CP is a high-energy molecule • After ATP is depleted, ADP is left • CP transfers energy to ADP, to regenerate ATP • CP supplies are exhausted in about 15-20 seconds Figure 6.10a

  3. Aerobic Respiration • Aerobic Respiration • Series of metabolic pathways that occur in the mitochondria • Glucose is broken down to carbon dioxide and water, releasing energy • This is a slower reaction that requires continuous oxygen 95% of the ATP used for muscle activity comes from aerobic respiration. Figure 6.10b

  4. Anaerobic Glycolysis • Anaerobic glycolysis • Reaction that breaks down glucose without oxygen • Glucose is broken down to pyruvic acid to produce some ATP • The waste product lactic acid is produced. Figure 6.10c

  5. Energy for Muscle Contraction • Anaerobic glycolysis (continued) • This reaction is not as efficient, but is fast • Huge amounts of glucose are needed • Lactic acid produces muscle fatigue Figure 6.10c

  6. Muscle Fatigue and Oxygen Debt • When a muscle is fatigued, it is unable to contract • The common reason for muscle fatigue is oxygen debt • Oxygen must be “repaid” to tissue to remove oxygen debt • Oxygen is required to get rid of accumulated lactic acid • Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less

  7. Isotonic contractions • Muscle shortens as it contracts • There is movement involved (entire muscle). • Ex. Knee bends, smile, flexing your biceps, rotate your arms • Isometric contractions : • There is tension on a muscle but no movement is made causing the length of the muscle to remain the same. • Myofilaments are unsuccessful in their sliding movements. • Example: Lifting a 400lb dresser alone, trying to lift immovable objects

  8. Muscle Tone • Some fibers are contracted even in a relaxed muscle • Different fibers contract at different times to provide muscle tone • The process of stimulating various fibers is under involuntary control • Flaccid-not firm • Atrophy-muscle is broken down

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