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Muscle Contraction I.ppt
- 1. Anatomy and PhysiologyI Muscle Structure and Contraction Instructor: Mary Holman
- 2. Muscle Functions • Producebody movements • Stabilize body position • Regulate organ volume • Move fluids and solid food and wastes in the body • Produce heat
- 3. Properties of MuscleTissue • Electrical excitability • Contractility • Extensibility • Elasticity
- 4. Connective Tissue Terms Relatedto Muscles Tendon Fascia Aponeurosis Epimysium Perimysium Endomysium
- 5. Fig. 9.1 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Aponeuroses Skeletal muscles Tendons muscle to muscle muscle to bone Skeletal Muscle
- 6. Fig. 9.2d Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Muscle Fascicles Muscle fibers (cells) Myofibrils Thick and thin filaments Actin & Myosin Fascia Epimysium Perimysium Endomysium Surrounded by
- 7. Fig. 9.2a Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Epimysium Perimysium Endomysium Tendon Fascia (covering muscle) Attachment of Muscle to Bone Fascicle
- 8. Fig. 9.2b Perimysium Endomysium Axon ofmotor neuron Fascicle Blood vessel Muscle fiber (Cell) Sarcolemma Nucleus Sarcoplasmic reticulum Fascicle of Skeletal Muscle
- 9. Fig. 9.2c Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Myofibril Nucleus Filaments Sarcoplasmic reticulum Skeletal Muscle Fiber - The Muscle Cell Sarcolemma Note:This slide does not show SR surrounding each myofibril! Fig 9.4 more accurate.
- 10. Fig. 9.3 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fascicle Perimysium Endomysium Muscle fiber Nucleus Myofibrils © Ed Reschke 320X SEM of a Fascicle (cross section)
- 11. Portion of a musclefiber Nuclei Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display © The McGraw-Hill Companies, Inc./Al Telser, photographer Skeletal Muscle Tissue 700x Fig. 5.28
- 12. Copyright © TheMcGraw-Hill Companies, Inc. Permission required for reproduction or display. © CNRI/SPL/Photo Researchers, Inc. SEM 3000x Human Striated Muscle Tissue Page 294 One sarcomere
- 13. Fig. 9.5a Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sarcomere © H.E. Huxley 16,000x
- 14. Fig. 9.4a Thick andThin filaments of the Myofibril
- 15. Fig. 9.5a Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sarcomere © H.E. Huxley 16,000x Z Z M A band I band I band H zone
- 16. Fig. 9.5b Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sarcomere I band Z line I band Z line Thin filaments Thick filaments A band Titin Actin Myosin
- 17. Three Types ofProtein Associated with the Muscle Fiber • Contractile – Actin – Myosin • Regulatory – Troponin – Tropomyosin • Structural – Titin – Dystrophin – Myomesin – Nebulin
- 18. Fig. 9.6 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Myosin heads which form bridges to Actin Actin molecule Tropomyosin Thin filament Myosin molecule Thick filament Troponin Thick and Thin Filaments Thin filament
- 19. Fig. 9.7 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleus Mitochondria Sarcolemma Sarcoplasm Nucleus Myofibrils Sarcoplasmic reticulum Openings into transverse tubules Thick and thin filaments Cisternae of sarcoplasmic reticulum Transverse tubule Triad Sarcoplasmic Reticulum and Transverse Tubules
- 20. Fig. 9.8a Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Axon branches Mitochondria Acetylcholine Synaptic vesicles Synaptic cleft Folded sarcolemma Motor end plate Myofibril of muscle fiber Muscle fiber nucleus Motor neuron axon The Neuro- Muscular Junction ( NMJ )
- 21. Fig. 9.8c Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mitochondria Acetylcholine Synaptic vesicles Synaptic cleft Neuromuscular Junction Folded sarcolemma Motor neuron Synaptic end bulb Synapse Muscle cell Motor end plate
- 22. Fig. 9.8b Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Motor neuron axon Muscle fiber Neuromuscular junction © McGraw-Hill Higher Education, Inc./Carol D. Jacobson Ph.D., Dept. Veterinary Anatomy, Iowa State University 500x Neuromuscular Junction
- 23. Copyright © TheMcGraw-Hill Companies, Inc. Permission required for reproduction or display. Motor neuron of motor unit 2 Motor neuron of motor unit 1 Skeletal muscle fibers Branches of motor neuron axon Muscle Fibers innervated by Two Motor Neurons
- 24. Copyright © TheMcGraw-Hill Companies, Inc. Permission required for reproduction or display. Motor neuron of motor unit 2 Motor neuron of motor unit 1 Skeletal muscle fibers Branches of motor neuron axon Muscle Fibers innervated by Two Motor Neurons
- 25. From: Principles ofAnatomy & Physiology Tortora & Grabowsky Neuromuscular Junction SEM 1650x
- 26. Events Leading upto Muscle Contraction • Nerve impulse arrives at end of motor nerve axon causing • Acetylcholine(ACh) release into synapse via exocytosis • ACh floods across synaptic gap and attaches to receptors on the sarcolemma • Permeability of sarcolemma changes and Na+ enters cell • A muscle impulse is triggered • Muscle impulse travels via the transverse tubules throughout the muscle cell • Ca++ diffuses from SR and binds to troponin on actin • Myosin cross bridges link with actin and muscle contracts NMJ Muscle fiber
- 27. Fig. 9.9 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Actin monomers Tropomyosin Troponin Thick filament - Myosin Thin filament Actin Relaxed muscle 1 ADP + P ADP + P Muscle contraction begins and continues if ATP is available and Ca++ level in the sarcoplasm is high Sliding Filament Theory
- 28. Fig. 9.9 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tropomyosin pulled aside ATP 2 Ca+2 binds to troponin Binding sites on actin exposed Ca+2 Ca+2 Ca+2 Exposed binding sites on actin molecules allow the muscle contraction cycle to occur ADP + P ADP + P Muscle Contraction Ca++ released from sarcoplasmic reticulum
- 29. Fig. 9.9 3 Myosinheads bind to actin forming cross-bridges ADP + P ADP + P P ADP P ADP Cross-bridges pull thin filament (power stroke), ADP and P released from myosin ADP + P 4
- 30. ATP ATP ATP ATP NewATP binds to myosin, releasing linkages 5 6 ATP splits, which provides power to“cock” the myosin cross-bridges ADP + P ADP + P Fig. 9.9
- 31. Fig. 9.10a Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Z line Z line Sarcomere Contracting Fully contracted Relaxed 2 3 1 A band Thin filaments Thick filaments
- 32. Fig. 9.10b Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Z line Z line Contracting Sarcomere A band © H.E. Huxley
- 33. Muscle Fiber Excitation •Nerve impulse arrives at axon terminal • Triggers release of Ach by exocytosis • ACh diffuses across synaptic cleft • ACh binds to receptors on muscle motor end plate • Sarcolemma becomes more permeable to Na+ • Na+ triggers release of muscle action potential • Muscle action potential travels along outside of sarcolemma and into T tubules • Action potential triggers Ca++ release from SR • Ca++ binds to troponin on thin filament • Tropomyosin is pulled aside, revealing binding sites • Myosin links to & pulls actin to contract muscle Muscle Fiber Relaxation • Acetylcholinesterase decomposes ACh in synapse • Action potential (impulse) ends • SR actively pumps Ca++ back into SR • Tropomyosin moves back to cover binding sites • Myosin heads detach • Muscle fiber returns to its longer resting length