tailieunhanh - PDQ Physiology - part 2

Sản xuất tương đối ít ATP nhưng sản xuất nó một cách nhanh chóng. 2. Ca + + thoáng qua là ngắn gọn và có cả một sự khởi đầu nhanh và nhanh chóng bù đắp. 3. Có cao hoạt động của lactate dehydrogenase, xúc tác phân tích về hoạt động pyruvate và thấp của các succinate dehydrogenase chu kỳ Krebs enzyme, xúc tác chuyển đổi của succinate | Chapter 2 Muscle 53 It produces relatively little ATP but produces it quickly. 2. The Ca transient is brief and has both a fast onset and a fast offset. 3. There is high activity of lactate dehydrogenase which catalyzes breakdown of pyruvate and low activity of the Krebs cycle enzyme succinate dehydrogenase which catalyzes the conversion of succinate to fumarate in the steps that lead to ATP production by oxidative phosphorylation. Functional features 1. Large force can be generated quickly but not maintained because fatigue sets in equally quickly. 2. Relaxation is rapid because actomyosin cross-bridges detach rapidly. Fast pink oxidative fibers type 2-A . Such fibers are sparse in human muscles and are also called intermediate fibers. They are of small diameter and contain many mitochondria. The presence of myoglobin makes them pink or red in appearance. Their dominant biochemical feature is that ATP is produced by both glycolytic and oxidative activity. ATP ADP ý GLYCOGEN----- D-GLUCOSE PYRUVATE ACETYL CoA i Krebs Cycle Oxidative phosphorylation ATP Their dominant functional feature is that large force can be generated quickly and maintained for a period of time that is intermediate between type 2-B and type 1 slow fibers. Slow oxidative fibers type 1 . These fibers are red in appearance because they have high capillary density and high myoglobin content. Their SR is 54 PDQ PHYSIOLOGY less prominent than it is in fast white glycolytic fibers. The extraocular muscles are rich in type-1 fiber muscles. Biochemical features 1. Metabolism is characterized by high oxidative activity. 2. The Ca transient is prolonged because these fibers have a lower Ca -ATPase activity. 3. They express myosin heavy chains with low ATPase activity. 4. Points 2 and 3 above with the presence of many mitochondria mean that slow fibers have a much greater capacity to generate ATP than to consume it. 5. Lactate dehydrogenase activity is low and succinate dehydrogenase activity is high .

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