Slides 21 - Muscle systems

extensor muscles extend the angle between two bones

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Unformatted text preview: r legs • Some spiders have leg joints that lack extensor muscles. - Extensor muscles extend the angle between two bones or body surfaces at a joint. - Flexor muscles decrease the angle between two bones or body surfaces at a joint. • Recoil of exoskeletal plates provides energy for extension Figure 12.23 4. Muscle energy metabolism • Muscle activity requires a lot of energy, mainly in the form of ATP - Actomyosin ATPase ‣ Cross-bridge cycling - Na+/K+ ATPase ‣ Reestablish ion gradients - Ca2+ ATPase ‣ Transport Ca2+ into SR Crystal structure Na+/K+ ATPase Crystal structure Ca2+ ATPase with 2 bound Ca2+ ions What fuels do muscles use? White muscle Red muscle Phosphagen system • Working muscle breaks down ATP. • ATP can be replenished by phosphagen system. • Creatine phosphokinase (CPK) breaks down PCr to Cr, transfers P to ADP to regenerate ATP • Some muscles use PCr shuttle Figure 2.41 Glycolysis to lactate • Glycolysis generates pyruvate from glucose. • Produces 2-3 ATP • Pathway produces ATP at very high rates, but at low efficiency • Pyruvate can then either enter mitochondria or be converted to lactate (by lactate dehydrogenase) • Lactate build up is associated with a decrease in muscle pH. • Glycolysis cannot be sustained indefinitely. Aerobic respiration • Occurs in mitochondria • Involves citric acid cycle • Electron transport and ATP production by F1F0 ATPase • Produces ~32 ATP/glucose • Slower than glycolysis, but more efficient • Can use a variety of fuels 5. Exercise physiology Factors that influence muscle fibre types and muscle size • The balance of fibre types within a muscle can vary in repose to: - genetic differences - exercise Exercise physiology & metabolism lab University of Melbourne • The size and number of fibres within a muscle can vary in response to: - genetic differences - exercise - drugs/hormones Fibre type- effects of genes • Transgenic mice (TG) that overexpress PPARδ - transcription factor involved in oxidative muscle development • Have a higher proportion...
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