Anatomy and Physiology I Muscle Structure and Contraction

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Anatomy and Physiology I Muscle Structure and Contraction Instructor: Mary Holman

Anatomy and Physiology I Muscle Structure and Contraction Instructor: Mary Holman

Muscle Functions • Produce body movements • Stabilize body position • Regulate organ volume

Muscle Functions • Produce body movements • Stabilize body position • Regulate organ volume • Move fluids and solid food and wastes in the body • Produce heat

Properties of Muscle Tissue • • Electrical excitability Contractility Extensibility Elasticity

Properties of Muscle Tissue • • Electrical excitability Contractility Extensibility Elasticity

Connective Tissue Terms Related to Muscles Tendon Fascia Aponeurosis Epimysium Perimysium Endomysium

Connective Tissue Terms Related to Muscles Tendon Fascia Aponeurosis Epimysium Perimysium Endomysium

Fig. 9. 1 Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction

Fig. 9. 1 Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Skeletal Muscle Aponeuroses muscle to muscle Skeletal muscles Tendons muscle to bone

Fig. 9. 2 d Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for

Fig. 9. 2 d Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Muscle Surrounded by Fascia Epimysium Fascicles Perimysium Muscle fibers (cells) Endomysium Myofibrils Thick and thin filaments Actin & Myosin

Fig. 9. 2 a Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for

Fig. 9. 2 a Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Attachment of Muscle to Bone Tendon Fascia (covering muscle) Epimysium Perimysium Endomysium Fascicle

Fig. 9. 2 b Fascicle of Skeletal Muscle Perimysium Copyright © The Mc. Graw-Hill

Fig. 9. 2 b Fascicle of Skeletal Muscle Perimysium Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Endomysium Fascicle Axon of motor neuron Blood vessel Muscle fiber (Cell) Sarcolemma Nucleus Sarcoplasmic reticulum

Fig. 9. 2 c Skeletal Muscle Fiber - The Muscle Cell Sarcoplasmic reticulum Copyright

Fig. 9. 2 c Skeletal Muscle Fiber - The Muscle Cell Sarcoplasmic reticulum Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Nucleus Myofibril Filaments Sarcolemma Note: This slide does not show SR surrounding each myofibril! Fig 9. 4 more accurate.

Fig. 9. 3 SEM of a Fascicle (cross section) Copyright © The Mc. Graw-Hill

Fig. 9. 3 SEM of a Fascicle (cross section) Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Perimysium Endomysium Fascicle Muscle fiber Nucleus Myofibrils © Ed Reschke 320 X

Fig. 5. 28 Skeletal Muscle Tissue 700 x Nuclei Portion of a muscle fiber

Fig. 5. 28 Skeletal Muscle Tissue 700 x Nuclei Portion of a muscle fiber © The Mc. Graw-Hill Companies, Inc. /Al Telser, photographer Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display

Page 294 Human Striated Muscle Tissue Copyright © The Mc. Graw-Hill Companies, Inc. Permission

Page 294 Human Striated Muscle Tissue Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. SEM 3000 x One sarcomere © CNRI/SPL/Photo Researchers, Inc.

Fig. 9. 5 a Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for

Fig. 9. 5 a Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Sarcomere © H. E. Huxley 16, 000 x

Fig. 9. 4 a Thick and Thin filaments of the Myofibril

Fig. 9. 4 a Thick and Thin filaments of the Myofibril

Fig. 9. 5 a Sarcomere I band A band I band Copyright © The

Fig. 9. 5 a Sarcomere I band A band I band Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Z M H zone © H. E. Huxley Z 16, 000 x

Fig. 9. 5 b Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for

Fig. 9. 5 b Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Sarcomere A band Titin I band Z line Thin filaments Actin Thick filaments Myosin

Three Types of Protein Associated with the Muscle Fiber • Contractile – Actin –

Three Types of Protein Associated with the Muscle Fiber • Contractile – Actin – Myosin • Regulatory – Troponin – Tropomyosin • Structural – Titin – Dystrophin – Myomesin – Nebulin

Fig. 9. 6 Thick and Thin Filaments Copyright © The Mc. Graw-Hill Companies, Inc.

Fig. 9. 6 Thick and Thin Filaments Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Myosin heads which form bridges to Actin Thin filament Thick filament Thin filament Troponin Tropomyosin Myosin molecule Actin molecule

Fig. 9. 7 Sarcoplasmic Reticulum and Transverse Tubules Copyright © The Mc. Graw-Hill Companies,

Fig. 9. 7 Sarcoplasmic Reticulum and Transverse Tubules Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Myofibrils Cisternae of sarcoplasmic reticulum Transverse tubule Nucleus Sarcoplasmic reticulum Openings into transverse tubules Mitochondria Thick and thin filaments Sarcoplasm Nucleus Sarcolemma Triad

Fig. 9. 8 a Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for

Fig. 9. 8 a Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Synaptic vesicles The Neuro. Muscular Junction ( NMJ ) Mitochondria Motor neuron axon Acetylcholine Synaptic cleft Folded sarcolemma Axon branches Muscle fiber nucleus Motor end plate Myofibril of muscle fiber

Fig. 9. 8 c Neuromuscular Junction Motor neuron Synaptic end bulb Copyright © The

Fig. 9. 8 c Neuromuscular Junction Motor neuron Synaptic end bulb Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Synapse Synaptic vesicles Muscle cell Motor end plate Mitochondria Acetylcholine Synaptic cleft Folded sarcolemma

Fig. 9. 8 b Neuromuscular Junction Copyright © The Mc. Graw-Hill Companies, Inc. Permission

Fig. 9. 8 b Neuromuscular Junction Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Motor neuron axon Muscle fiber Neuromuscular junction © Mc. Graw-Hill Higher Education, Inc. /Carol D. Jacobson Ph. D. , Dept. Veterinary Anatomy, Iowa State University 500 x

Muscle Fibers innervated by Two Motor Neurons Copyright © The Mc. Graw-Hill Companies, Inc.

Muscle Fibers innervated by Two Motor Neurons Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Motor neuron of motor unit 2 Motor neuron of motor unit 1 Branches of motor neuron axon Skeletal muscle fibers

Muscle Fibers innervated by Two Motor Neurons Copyright © The Mc. Graw-Hill Companies, Inc.

Muscle Fibers innervated by Two Motor Neurons Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Motor neuron of motor unit 2 Motor neuron of motor unit 1 Branches of motor neuron axon Skeletal muscle fibers

Neuromuscular Junction SEM 1650 x From: Principles of Anatomy & Physiology Tortora & Grabowsky

Neuromuscular Junction SEM 1650 x From: Principles of Anatomy & Physiology Tortora & Grabowsky

Events Leading up to Muscle Contraction NMJ Muscle fiber • Nerve impulse arrives at

Events Leading up to Muscle Contraction NMJ Muscle fiber • 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

Fig. 9. 9 Sliding Filament Theory Relaxed muscle Copyright © The Mc. Graw-Hill Companies,

Fig. 9. 9 Sliding Filament Theory Relaxed muscle Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Tropomyosin Troponin Actin monomers ADP + P Thin filament Actin ADP + P Thick filament - Myosin 1 Muscle contraction begins and continues if ATP is available and Ca++ level in the sarcoplasm is high

Fig. 9. 9 Muscle Contraction Ca++ released from sarcoplasmic reticulum Ca+2 binds to troponin

Fig. 9. 9 Muscle Contraction Ca++ released from sarcoplasmic reticulum Ca+2 binds to troponin Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Tropomyosin pulled aside ATP Binding sites on actin exposed Ca+2 ADP + P Ca+2 2 Exposed binding sites on actin molecules allow the muscle contraction cycle to occur

Fig. 9. 9 ADP + P 3 ADP + P Myosin heads bind to

Fig. 9. 9 ADP + P 3 ADP + P Myosin heads bind to actin forming cross-bridges ADP P ADP + P 4 Cross-bridges pull thin filament (power stroke), ADP and P released from myosin

Fig. 9. 9 ATP ATP 5 New ATP binds to myosin, releasing linkages ADP

Fig. 9. 9 ATP ATP 5 New ATP binds to myosin, releasing linkages ADP + 6 P ADP + P ATP splits, which provides power to“cock” the myosin cross-bridges

Fig. 9. 10 a Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for

Fig. 9. 10 a Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Sarcomere A band Z line 1 Relaxed Thin filaments Thick filaments 2 Contracting 3 Fully contracted

Fig. 9. 10 b Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for

Fig. 9. 10 b Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Contracting Sarcomere A band Z line © H. E. Huxley

Muscle Fiber Excitation • Nerve impulse arrives at axon terminal • Triggers release of

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