Three major types usually recognized with various

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Unformatted text preview: ments does not change. Cross-sections of skeletal muscle can reveal different fiber types when stained histochemically. Three major types usually recognized (with various names): Type I or “slow fibers” (S) have many mitochondria and much myoglobin (dark). Type IIa or “fast intermediate fibers” (I) also have glycogen (less stain). Type IIb or “fast glycolytic fibers” (F) have few mitochondria and little myoglobin, but much glycogen (poorly staining), allowing anaerobic metabolism but tiring quickly. CONTAIN DIFF TYPES OF MITOCHONDRIA AND MYOGLOBIN --- IN STAINING, YOU CAN TELL THE DIFF B/W HOW MUCH IS THERE!!! Differing amounts of mitochon/ myoglobin influence how well muscle cell can contract. Lighter stained - less dense can't sustain too much, but can happen quickly (ex: eyelids) Fig. 10-15 Darker = more dense = slower but sustain more --- for running, exercising, etc! Within large skeletal muscle are a few small fascicles specialized as sensory receptors called muscle spindles...
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