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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
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
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- Spring '14