Muscle Physiology 2016 A&P Past Paper PDF

PowerPoint Lecture Outlines to accompany Hole’s Human Anatomy and Physiology Eleventh Edition Shier ⬥ Butler ⬥ Lewis Chapter 9 Copyright...

PowerPoint Lecture Outlines to accompany Hole’s Human Anatomy and Physiology Eleventh Edition Shier ⬥ Butler ⬥ Lewis Chapter 9 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or 1 display.  Chapter 9 Muscular System Three Types of Muscle Tissues Skeletal Muscle Cardiac Muscle usually attached to wall of heart bones not under under conscious conscious control control striated striated Smooth Muscle walls of most viscera, blood vessels, skin not under conscious control not striated 2  Structure of a Skeletal Muscle Skeletal Muscle organ of the muscular system - skeletal muscle tissue - nervous tissue - blood - connective tissues fascia tendons aponeuroses 3  Connective Tissue Coverings epimysium perimysium fascicles endomysium muscle fascicles muscle fibers myofibrils thick and thin filaments 4  Skeletal Muscle Fibers sarcolemma sacroplasm sarcoplasmic reticulum transverse tubule triad cisternae of sarcoplasmic reticulum transverse tubule myofibril actin filaments myosin filaments sarcomere 5  Sarcomere I bands A bands H zone Z lines M line 6  Myofilaments Thick Filaments Thin Filaments composed of myosin composed of actin cross-bridges associated with troponin and tropomyosin 7  Neuromuscular Junction also known as myoneural junction site where an axon and muscle fiber meet motor neuron motor end plate synapse synaptic cleft synaptic vesicles neurotransmitters 8  Motor Unit single motor neuron all muscle fibers controlled by motor neuron 9  Stimulus for Contraction acetylcholine (ACh) nerve impulse causes release of ACh from synaptic vesicles ACh binds to ACh receptors on motor end plate generates a muscle impulse muscle impulse eventually reaches sarcoplasmic reticulum and the cisternae 10  Excitation Contraction Coupling muscle impulses cause sarcoplasmic reticulum to release calcium ions into cytosol calcium binds to troponin to change its shape position of tropomyosin is altered binding sites on actin are exposed actin and myosin molecules bind 11 Sliding Filament Model of Muscle Contraction When sarcromeres shorten, thick and thin filaments slide past one another H zones and I bands narrow Z lines move closer together 12  Cross-bridge Cycling myosin cross-bridge attaches to actin binding site myosin cross-bridge pulls thin filament ADP and phosphate released from myosin new ATP binds to myosin linkage between actin and myosin cross-bridge break ATP splits myosin cross-bridge goes back to original position 13  Relaxation acetylcholinesterase – rapidly decomposes Ach remaining in the synapse muscle impulse stops stimulus to sarcolemma and muscle fiber membrane ceases calcium moves back into sarcoplasmic reticulum myosin and actin binding prevented muscle fiber relaxes 14  Major Events of Muscle Contraction and Relaxation 15  Energy Sources for Contraction 1) Creatine phosphate 2) Cellular respiration creatine phosphate – stores energy that quickly converts ADP to ATP 16  Oxygen Supply and Cellular Respiration Anaerobic Phase glycolysis occurs in cytoplasm produces little ATP Aerobic Phase citric acid cycle electron transport chain occurs in the mitochondria produces most ATP myoglobin stores extra oxygen 17  Oxygen Debt Oxygen debt – amount of oxygen needed by liver cells to use the accumulated lactic acid to produce glucose oxygen not available glycolysis continues pyruvic acid converted to lactic acid liver converts lactic acid to glucose 18  Muscle Fatigue inability to contract commonly caused from decreased blood flow ion imbalances across the sarcolemma accumulation of lactic acid cramp – sustained, involuntary muscle contraction 19  Heat Production by-product of cellular respiration muscle cells are major source of body heat blood transports heat throughout body 20 Length-Tension Relationship 21  Recruitment of Motor Units recruitment - increase in the number of motor units activated whole muscle composed of many motor units more precise movements are produced with fewer muscle fibers within a motor unit as intensity of stimulation increases, recruitment of motor units continues until all motor units are activated 22  Sustained Contractions smaller motor units (smaller diameter axons) - recruited first larger motor units (larger diameter axons) - recruited later produce smooth movements muscle tone – continuous state of partial contraction 23