Functions of Muscles • Body movement • Maintenance of posture • Ventilation • Thermogenesis • Communication • Constriction of organs and lumens • Heartbeat 1 2 3 4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tendon Fascia Skeletal muscle Muscle fascicle Nerve Blood vessels Epimysium Perimysium Endomysium Muscle fiber Muscle fascicle Perimysium Muscle fiber 5 6 (a) 7 8 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproducIon or display. Nucleus Sarcomere 5 Z disc M line 4 H band 3 I band A band I band 2 Individual myofibrils 1 (a) Sarcomere I band A band I band H band Thick filament Thin filament M line Tin Z disc ElasIc filament (b) Z disc a: Visuals Unlimited 9 10 11 12 13 14 15 16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproducIon or display. Muscle fiber Nucleus A band I band Z disc Mitochondria Openings into transverse tubules Sarcoplasmic reIculum T riad: T erminal cisternae T ransverse tubule Sarcolemma Myofibrils Sarcoplasm Myofilaments 17 18 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproducIon or display. Terminal T tubule cisterna of SR T tubule Sarcoplasmic reIculum Ca2+ Ca2+ 6 AcIon potenIals propagated 7 Calcium released from down T tubules terminal cisternae Acve sites Troponin 2+ Ca Tropomyosin Acn Thin filament Myosin Ca2+ 8 Binding of calcium 9 Shi[ing of tropomyosin; to troponin exposure of acIve sites on acIn 19 20 21 22 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproducIon or display. Spinal cord Motor neuron 1 Motor neuron 2 Neuromuscular juncon Skeletal muscle fibers 23 24 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproducIon or display. Threshold SImulus voltage 1 2 3 4 5 6 7 8 9 Smuli to nerve Proporon of nerve fibers excited Maximum contracIon Tension 1 2 3 4 5 6 7 8 9 25 Responses of muscle 26 27 28 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproducIon or display. Muscle develops Muscle shortens, Muscle lengthens tension but does tension remains while maintaining not shorten constant tension Movement No movement Movement (a) Isometric contracIon (b) Isotonic concentric contracIon (c) Isotonic eccentric contracIon 29 30 31 32 33 34 .