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Muscle Histology

Muscle Histology. Connective coverings. Muscles are covered with fascia which separates muscles. Deep fascia separates muscles from each other, superficial fascia-from skin. Fascia are continuous with tendons which are continuous with ____________. Smaller picture.

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Muscle Histology

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  1. Muscle Histology

  2. Connective coverings • Muscles are covered with fascia which separates muscles. Deep fascia separates muscles from each other, superficial fascia-from skin. • Fascia are continuous with tendons which are continuous with ____________

  3. Smaller picture • Muscles are grouped in to fascicles that are covered with a sheath of connective tissue called perimysium. • Fascicles are divided into muscle fibers, each surrounded by the endomysium • Blood and nerves reach the muscle through the endomysium

  4. Cellular level • Muscle Fibers are made of myofibrils • Plasma membrane= sarcolema • Endoplasmic reticulum=sarcoplasmic reticulum • Each sarcoplasmic reticulum encases ooodles of myofibrils • Myofibrils are divided into sarcomeres (p117) see drawing!

  5. Muscle Contractions • Motor Unit: A single nerve ending and all the muscle fibers attached to it • With a nerve impulse- muscle fibers contract completely. “all or none” • Does a muscle have to contract completely? • Partial contraction of a muscle comes from only contracting a portion of the fibers

  6. Exercise • Atrophy- from lack of use, muscle fibers are replaced with adipose and fibrous tissue • Can cause muscle fibers to shorten enough to force the body to contort. • Hypertrophy-more myofibrils develop with more use

  7. Going the Distance, or not? • Slow twitch- less fibers per motor unit • Largely aerobic-extra mitochondria, extra capillaries • Presence of Myoglobin • A dark, red oxygen carrying pigment • Fast Twitch- more fibers per motor unit • Few mitochondria • Largley anerobic • Easily hits maximum tension

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