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Muscle Physiology Chapter 11
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Connective Tissue Components
Muscle cell = muscle fiber Endomysium – covers muscle fiber Perimysium – binds groups of muscle fibers (fasicles) Epimysium – covers the entire muscle Tendon – fibrous tissue that connects muscle to bone Aponeurosis – broad, flat sheet of connective tissue Fascia – fibrous CT surrounding muscle and tendon
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Overview of Muscle Cell
Muscle cell = muscle fiber Sarcolemma = plasma membrane Sarcoplasm = cytoplasm Sarcoplasmic reticulum (SR) = network of tubules and sacs Multi-nucleated, multiple mitochondrion Bundles of myofibrils extend lengthwise & fill sarcoplasm Composed of thick and thin myofilaments
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Sarcomere Contractile unit of a muscle fiber
each myofibril consists of many sarcomeres
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Myofilaments Myofibrils – made up of 1000s of thin and thick myofilaments Thin filaments Actin Tropomyosin Troponin Thick filaments myosin
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Actin molecules strung together like beads to form two fibrous strands that twist around each other
Actin and myosin molecules have a chemical attraction to each other At rest – actin active sites are covered by tropomyosin; tropomyosin held in place by troponin Myosin filaments – heads stick out from bundles; attracted to actin
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Muscle Relaxation Nerve impulse is complete Ca2+ is pumped back into the sacs of the SR Ca2+ is stripped from the troponin tropomyosin covers the actin’s active site Myosin heads can no longer bind with actin muscle fiber returns to its resting length
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Rigor Mortis “stiffness of death”
Lack of ATP after death causes cross bridges to “stick”
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http://highered. mcgraw-hill
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Aerobic vs. Anaerobic Respiration
Oxygen-requiring process Produces maximum amount of ATP from one glucose molecule Anaerobic Respiration Does not require oxygen Short-term, rapid process to re-synthesize ATP Produces lactic acid Burning/soreness in muscles
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Isotonic vs Isometric Contractions
Isotonic – tension remains the same; length of the muscle changes Concentric contraction: muscle shortens (contracts) Eccentric contraction : muscle lengthens Isometric – tension changes; length of the muscle remains the same Myosin heads unable to move thin filaments Static tension
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