PowerPoint® Lecture Slidesprepared byBarbara Heard,Atl.docx
- 1. PowerPoint® Lecture Slides prepared by Barbara Heard, Atlantic Cape Community College C H A P T E R © 2013 Pearson Education, Inc. © Annie Leibovitz/Contact Press Images 9 Muscles and Muscle Tissue: Part A © 2013 Pearson Education, Inc. Muscle TissueNearly half of body's massTransforms chemical forceThree typesSkeletalCardiacSmoothMyo, mys, and sarco - prefixes for muscle © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Types of Muscle TissueSkeletal muscles Organs attached to
- 2. bones and skinElongated cells called muscle fibersStriated (striped) Voluntary (i.e., conscious control)Contract rapidly; tire easily; powerfulRequire nervous system stimulation © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Types of Muscle TissueCardiac muscleOnly in heart; bulk of heart walls StriatedCan contract without nervous system stimulation Involuntary © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Types of Muscle TissueSmooth muscleIn walls of hollow organs, e.g., stomach, urinary bladder, and airwaysNot striatedCan contract without nervous system stimulation Involuntary © 2013 Pearson Education, Inc. *
- 3. © 2013 Pearson Education, Inc. Table 9.3 Comparison of Skeletal, Cardiac, and Smooth Muscle (1 of 4) © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Special Characteristics of Muscle TissueExcitability (responsiveness): ability to receive and respond to stimuliContractility: ability to shorten forcibly when stimulatedExtensibility: ability to be stretched Elasticity: ability to recoil to resting length © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Muscle FunctionsFour important functionsMovement of bones or fluids (e.g., blood)Maintaining posture and body position Stabilizing jointsHeat generation (especially skeletal muscle)Additional functionsProtects organs, forms valves, controls pupil size, causes "goosebumps" © 2013 Pearson Education, Inc. *
- 4. © 2013 Pearson Education, Inc. Skeletal MuscleConnective tissue sheaths of skeletal muscleSupport cells; reinforce whole muscleExternal to internalEpimysium: dense irregular connective tissue surrounding entire muscle; may blend with fascia Perimysium: fibrous connective tissue surrounding fascicles (groups of muscle fibers)Endomysium: fine areolar connective tissue surrounding each muscle fiber © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Figure 9.1 Connective tissue sheaths of skeletal muscle: epimysium, perimysium, and endomysium. Bone Tendon Epimysium Epimysium Perimysium Endomysium Muscle fiber in middle of a fascicle Blood vessel Perimysium wrapping a fascicle Endomysium (between individual
- 5. muscle fibers) Muscle fiber Perimysium Fascicle © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Table 9.1 Structure and Organizational Levels of Skeletal Muscle (1 of 3) © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Table 9.1 Structure and Organizational Levels of Skeletal Muscle (2 of 3) © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc.
- 6. Table 9.1 Structure and Organizational Levels of Skeletal Muscle (3 of 3) © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Microscopic Anatomy of a Skeletal Muscle FiberLong, cylindrical cell 10 to 100 µm in diameter; up to 30 cm longMultiple peripheral nucleiSarcolemma = plasma membraneSarcoplasm = cytoplasmGlycosomes for glycogen storage, myoglobin for O2 storageModified structures: myofibrils, sarcoplasmic reticulum, and T tubules © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. MyofibrilsDensely packed, rodlike elements ~80% of cell volume Contain sarcomeres - contractile units Sarcomeres contain myofilamentsExhibit striations - perfectly aligned repeating series of dark A bands and light I bands © 2013 Pearson Education, Inc. *
- 7. © 2013 Pearson Education, Inc. Figure 9.2b Microscopic anatomy of a skeletal muscle fiber. Diagram of part of a muscle fiber showing the myofibrils. One myofibril extends from the cut end of the fiber. Sarcolemma Mitochondrion Myofibril Nucleus Light I band Dark A band © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. StriationsH zone: lighter region in midsection of dark A band where filaments do not overlap M line: line of protein myomesin bisects H zoneZ disc (line): coin-shaped sheet of proteins on midline of light I band that anchors thin filaments and connects myofibrils to one anotherThick filaments: run
- 8. entire length of an A bandThin filaments: run length of I band and partway into A bandSarcomere: region between two successive Z discs © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. SarcomereSmallest contractile unit (functional unit) of muscle fiberAlign along myofibril like boxcars of trainContains A band with ½ I band at each endComposed of thick and thin myofilaments made of contractile proteins © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Figure 9.2c Microscopic anatomy of a skeletal muscle fiber. Small part of one myofibril enlarged to show the myofilaments responsible for the banding pattern. Each sarcomere extends from one Z disc to the next. Thin (actin)
- 9. filament Z disc H zone Z disc Thick (myosin) filament I band A band I band M line Sarcomere © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Figure 9.2d Microscopic anatomy of a skeletal muscle fiber. Enlargement of one sarcomere (sectioned length- wise). Notice the myosin heads on the thick filaments. Z disc Sarcomere M line Z disc Thin (actin) filament Elastic (titin)
- 10. filaments Thick (myosin) filament © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Myofibril Banding PatternOrderly arrangement of actin and myosin myofilaments within sarcomereActin myofilaments = thin filamentsExtend across I band and partway in A bandAnchored to Z discsMyosin myofilaments = thick filamentsExtend length of A bandConnected at M line © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Ultrastructure of Thick FilamentComposed of protein myosinEach composed of 2 heavy and four light polypeptide chainsMyosin tails contain 2 interwoven, heavy polypeptide chainsMyosin heads contain 2 smaller, light polypeptide chains that act as cross bridges during contraction Binding sites for actin of thin filamentsBinding sites for ATPATPase enzymes © 2013 Pearson Education, Inc.
- 11. * © 2013 Pearson Education, Inc. Ultrastructure of Thin FilamentTwisted double strand of fibrous protein F actinF actin consists of G (globular) actin subunits G actin bears active sites for myosin head attachment during contractionTropomyosin and troponin - regulatory proteins bound to actin © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Longitudinal section of filaments within one sarcomere of a myofibril Thick filament Thin filament In the center of the sarcomere, the thick filaments lack myosin heads. Myosin heads are present only in areas of myosin-actin overlap. Thick filament. Thin filament Each thick filament consists of many myosin molecules whose heads protrude at opposite�ends of the filament. A thin filament consists of two strands of actin subunits twisted into a helix plus two types of
- 12. regulatory proteins (troponin and tropomyosin). Portion of a thick filament Portion of a thin filament Myosin head Tropomyosin Troponin Actin Actin-binding sites ATP- binding site Heads Tail Flexible hinge region Myosin molecule Actin subunits Actin subunits Active sites for myosin attachment Figure 9.3 Composition of thick and thin filaments. © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Structure of MyofibrilElastic filamentComposed of protein titinHolds thick filaments in place; helps recoil after stretch; resists excessive stretchingDystrophinLinks thin filaments to proteins of sarcolemmaNebulin, myomesin, C proteins bind filaments or sarcomeres together; maintain alignment © 2013 Pearson Education, Inc.
- 13. * © 2013 Pearson Education, Inc. Sarcoplasmic Reticulum (SR)Network of smooth endoplasmic reticulum surrounding each myofibrilMost run longitudinallyPairs of terminal cisterns form perpendicular cross channelsFunctions in regulation of intracellular Ca2+ levelsStores and releases Ca2+ © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. T TubulesContinuations of sarcolemmaLumen continuous with extracellular spaceIncrease muscle fiber's surface areaPenetrate cell's interior at each A band–I band junctionAssociate with paired terminal cisterns to form triads that encircle each sarcomere © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc.
- 14. Figure 9.5 Relationship of the sarcoplasmic reticulum and T tubules to myofibrils of skeletal muscle. Part of a skeletal muscle fiber (cell) Myofibril Sarcolemma I band A band I band Z disc H zone Z disc M line Sarcolemma Triad: • T tubule • Terminal cisterns of the SR (2) Tubules of the SR Myofibrils Mitochondria © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Triad RelationshipsT tubules conduct impulses deep into muscle fiber; every sarcomere Integral proteins protrude into intermembrane space from T tubule and SR cistern membranes
- 15. and connect with each otherT tubule integral proteins act as voltage sensors and change shape in response to voltage changesSR integral proteins are channels that release Ca2+ from SR cisterns when voltage sensors change shape © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Sliding Filament Model of ContractionGeneration of force Does not necessarily cause shortening of fiberShortening occurs when tension generated by cross bridges on thin filaments exceeds forces opposing shortening © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Sliding Filament Model of ContractionIn relaxed state, thin and thick filaments overlap only at ends of A bandSliding filament model of contractionDuring contraction, thin filaments slide sin overlap moreOccurs © 2013 Pearson Education, Inc. *
- 16. © 2013 Pearson Education, Inc. Sliding Filament Model of ContractionMyosin heads bind to actin; sliding begins Cross bridges form and break several times, ratcheting thin filaments toward center of sarcomereCauses shortening of muscle fiberPulls Z discs toward M line I bands shorten; Z discs closer; H zones disappear; A bands move closer (length stays same) © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Figure 9.6 Sliding filament model of contraction. Slide 2 1 Fully relaxed sarcomere of a muscle fiber Z H Z I I A © 2013 Pearson Education, Inc.
- 17. * © 2013 Pearson Education, Inc. Figure 9.6 Sliding filament model of contraction. Slide 3 2 Fully contracted sarcomere of a muscle fiber Z Z I I A © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. The Nerve Stimulus and Events at the Neuromuscular Junction Skeletal muscles stimulated by somatic motor neurons Axons of motor neurons travel from central nervous system via nerves to skeletal muscleEach axon forms several branches as it enters muscle Each axon ending forms neuromuscular junction with single muscle fiberUsually only one per muscle fiber © 2013 Pearson Education, Inc.
- 18. * © 2013 Pearson Education, Inc. Events of Excitation-Contraction (E-C) Coupling AP propagated along sarcomere to T tubulesVoltage-sensitive proteins stimulate Ca2+ release from SR Ca2+ necessary for contraction © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Role of Calcium (Ca2+) in ContractionAt low intracellular Ca2+ concentrationTropomyosin blocks active sites on actinMyosin heads cannot attach to actinMuscle fiber relaxed © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Role of Calcium (Ca2+) in ContractionAt higher intracellular Ca2+ concentrationsCa2+ binds to troponin Troponin changes shape and moves tropomyosin away from myosin-binding
- 19. sitesMyosin heads bind to actin, causing sarcomere shortening and muscle contractionWhen nervous stimulation ceases, Ca2+ pumped back into SR and contraction ends © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Cross Bridge CycleContinues as long as Ca2+ signal and adequate ATP presentCross bridge formation—high-energy myosin head attaches to thin filamentWorking (power) stroke— myosin head pivots and pulls thin filament toward M line © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Cross Bridge CycleCross bridge detachment—ATP attaches to myosin head and cross bridge detaches"Cocking" of myosin head—energy from hydrolysis of ATP cocks myosin head into high-energy state © 2013 Pearson Education, Inc. *
- 20. © 2013 Pearson Education, Inc. Figure 9.12 The cross bridge cycle is the series of events during which myosin heads pull thin filaments toward the center of the sarcomere. Slide 1 Actin Ca2+ Thin filament Myosin cross bridge Thick filament Myosin ATP hydrolysis In the absence of ATP, myosin heads will not detach, causing rigor mortis. *This cycle will continue as long as ATP is available and Ca2+ is bound to troponin. Cross bridge formation. Energized myosin head attaches to an actin myofilament, forming a cross bridge. Cocking of the myosin head. As ATP is hydrolyzed to ADP and Pi, the myosin head returns to its prestroke high-energy, or “cocked,” position. * Cross bridge detachment. After ATP attaches to myosin, the link between myosin and actin weakens, and the myosin head detaches (the cross bridge “breaks”). The power (working) stroke. ADP and Pi are released and the myosin head pivots and bends, changing to its bent low-energy state. As a result it pulls the actin filament toward the M line. 1
- 21. 2 3 4 © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Figure 9.12 The cross bridge cycle is the series of events during which myosin heads pull thin filaments toward the center of the sarcomere. Slide 2 Actin Thin filament Myosin cross bridge Thick filament Myosin Cross bridge formation. Energized myosin head attaches to an actin myofilament, forming a cross bridge. 1 © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc.
- 22. Figure 9.12 The cross bridge cycle is the series of events during which myosin heads pull thin filaments toward the center of the sarcomere. Slide 3 The power (working) stroke. ADP and Pi are released and the myosin head pivots and bends, changing to its bent low- energy state. As a result it pulls the actin filament toward the M line. 2 © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Figure 9.12 The cross bridge cycle is the series of events during which myosin heads pull thin filaments toward the center of the sarcomere. Slide 4 Cross bridge detachment. After ATP attaches to myosin, the link between myosin and actin weakens, and the myosin head detaches (the cross bridge “breaks”). 3 © 2013 Pearson Education, Inc. *
- 23. © 2013 Pearson Education, Inc. Figure 9.12 The cross bridge cycle is the series of events during which myosin heads pull thin filaments toward the center of the sarcomere. Slide 5 Cocking of the myosin head. As ATP is hydrolyzed to ADP and Pi, the myosin head returns to its prestroke high-energy, or “cocked,” position. * 4 ATP hydrolysis *This cycle will continue as long as ATP is available and Ca2+ is bound to troponin. © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc. Figure 9.12 The cross bridge cycle is the series of events during which myosin heads pull thin filaments toward the center of the sarcomere. Slide 6 A&P Flix™: The Cross Bridge Cycle PLAY Actin Ca2+ Thin filament Myosin cross bridge
- 24. Thick filament Myosin ATP hydrolysis In the absence of ATP, myosin heads will not detach, causing rigor mortis. *This cycle will continue as long as ATP is available and Ca2+ is bound to troponin. Cross bridge formation. Energized myosin head attaches to an actin myofilament, forming a cross bridge. Cocking of the myosin head. As ATP is hydrolyzed to ADP and Pi, the myosin head returns to its prestroke high-energy, or “cocked,” position. * Cross bridge detachment. After ATP attaches to myosin, the link between myosin and actin weakens, and the myosin head detaches (the cross bridge “breaks”). The power (working) stroke. ADP and Pi are released and the myosin head pivots and bends, changing to its bent low-energy state. As a result it pulls the actin filament toward the M line. 1 2 3 4 © 2013 Pearson Education, Inc. * © 2013 Pearson Education, Inc.
- 25. Homeostatic ImbalanceRigor mortisCross bridge detachment requires ATP3–4 hours after death muscles begin to stiffen with weak rigidity at 12 hours post mortemDying cells take in reak cross bridges © 2013 Pearson Education, Inc. *