Short Term Energy

As the phosphagen system is exhausted, the muscles shift to anaerobic fermentation to "buy time" until cardiopulmonary function can catch up with the muscle's oxygen demand. During this period, the muscles obtain glucose from the blood and their own stored glycogen. The pathway from glycogen to lactic acid, called the glycogen-lactic acid

Saladin: Anatomy & I 11. Muscular Tissue I Text I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

428 Part Two Support and Movement

428 Part Two Support and Movement

10 seconds 40 seconds

Duration of exercise

10 seconds 40 seconds

Duration of exercise

ATP synthesis

Aerobic respiration

Aerobic respiration using oxygen from myoglobin

Phosphagen system

Glycogen— lactic acid system (anaerobic fermentation)

Aerobic respiration

Repayment of oxygen debt

Figure 11.18 Phases of ATP Production During Exercise.

Creatine Kinase Pathway
Figure 11.19 The Phosphagen System. Two enzymes, myokinase and creatine kinase, generate ATP in the absence of oxygen. Myokinase borrows phosphate groups from ADP, and creatine kinase borrows them from creatine phosphate, to convert an ADP to ATP.

system, produces enough ATP for 30 to 40 seconds of maximum activity. To play basketball or to run completely around a baseball diamond, for example, depends heavily on this energy-transfer system.

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Essentials of Human Physiology

Essentials of Human Physiology

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