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Types and Characteristics of Skeletal Muscle Fibers

Learn about the different types of skeletal muscle fibers, including their energy production and contraction speed. Discover the characteristics and functions of slow oxidative, fast glycolytic, and fast oxidative fibers.

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Types and Characteristics of Skeletal Muscle Fibers

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  1. PART 2 Muscle Tissue

  2. Types of Skeletal Muscle Fibers • Skeletal muscle fibers are categorized according to • How they manufacture energy (ATP) • How quickly they contract

  3. Types of Skeletal Muscle Fibers • Skeletal muscle fibers • Are divided into 3 classes • Slow oxidative fibers (Type I) • Red Slow twitch • Fast glycolytic fibers (Type IIx) • White fast-twitch • Fast oxidative fibers (Type IIa) • Intermediate fibers

  4. Types of Skeletal Muscle Fibers • Slow oxidative fibers (Type I) • Red color due to abundant myoglobin • Obtain energy from aerobic metabolic reactions • Contain a large number of mitochondria • Richly supplied with capillaries • Contract slowly and resistant to fatigue • Fibers are small in diameter

  5. Types of Skeletal Muscle Fibers • Fast glycolytic fibers (Type IIx) • Contain little myoglobin and few mitochondria • About twice the diameter of slow-oxidative fibers • Contain more myofilaments and generate more power • Depend on anaerobic pathways • Contract rapidly and tire quickly

  6. Types of Skeletal Muscle Fibers • Fast oxidative fibers (Type IIa) • Have an intermediate diameter • Contract quickly like fast glycolytic fibers • Are oxygen-dependent • Have high myoglobin content and rich supply of capillaries • Somewhat fatigue-resistant • More powerful than slow oxidative fibers

  7. Table 10.2 (1 of 3)

  8. Table 10.2 (2 of 3)

  9. Table 10.2 (3 of 3)

  10. Disorders of Muscle Tissue • Muscle tissues experience few disorders • Heart muscle is the exception • Skeletal muscle • Remarkably resistant to infection • Smooth muscle • Problems stem from external irritants

  11. Disorders of Muscle Tissue • Muscular dystrophy • A group of inherited muscle destroying disease • Affected muscles enlarge with fat and connective tissue • Muscles degenerate • Types of muscular dystrophy • Duchenne muscular dystrophy • Myotonic dystrophy

  12. Disorders of Muscle Tissue • Myofascial pain syndrome • Pain is caused by tightened bands of muscle fibers • Fibromyalgia • A mysterious chronic-pain syndrome • Affects mostly women • Symptoms – fatigue, sleep abnormalities, severe musculoskeletal pain, and headache

  13. Muscle Tissue Throughout Life • Muscle tissue develops from myoblasts • Myoblasts fuse to form skeletal muscle fibers • Skeletal muscles contract by the seventh week of development

  14. Muscle Tissue Throughout Life • Cardiac muscle • Pumps blood three weeks after fertilization • Satellite cells • Surround skeletal muscle fibers • Resemble undifferentiated myoblasts • Fuse into existing muscle fibers to help them grow

  15. Muscle Tissue Throughout Life • With increased age • Amount of connective tissue increases in muscles • Number of muscle fibers decreases • Loss of muscle mass with aging • Decrease in muscular strength by 50% by age 80 • Sarcopenia – muscle wasting

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