Locomotion [2014]

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  • 1. LOCOMOTION &SUPPORTDr. M.Azzopardi

2. OVERVIEWA)TYPES OF MUSCLESB) STRIATED MUSCLEC) HYDROSTATIC SKELETONS, EXOSKELETONSAND ENDOSKELETONSD) THE VERTEBRAL COLUMN 3. Three kinds of muscle:SmoothUnstriated,UnstripedorInvoluntarySkeletal,Striated,Striped orVoluntaryCardiac 4. Three kinds of muscle:1. Smooth Musclecontracts slowly &fatigues slowly2. Cardiac Muscleis self-stimulating &does not fatigue3. Skeletal Musclecontracts quickly &fatigues quicklyGap junctions 5. Cardiac muscle:is striatedcells: are smaller than skeletal have one nucleus branch and interdigitate:can withstand tearing 6. Functions of the Intercalated discs:1. add to the strength of cardiacmuscle2. provide strong mechanicaladhesions between adjacentcells3. have GAP JUNCTIONS allowing therapid spread of a depolarisationinitiated at one point in the heart 7. OVERVIEWA) TYPES OF MUSCLESB) STRIATED MUSCLEC) HYDROSTATIC SKELETONS,EXOSKELETONS ANDENDOSKELETONSD) THE VERTEBRAL COLUMN 8. Tendons attach skeletal muscle to bone: 9. Organisation of Skeletal Muscle1. Muscle 2. Muscle fibre bundles[groups of 10-100 or moremuscle fibers]3. Muscle fibre4. Myofibril5. Myofilamentsmuscle cellcomposed ofmyofilamentscontractile proteins:actin & myosin 10. Organisation of Skeletal MuscleCells aremultinucleateEach muscle fibre is composed of MYOFIBRILS 11. Structure of a muscle fibreEndoplasmicreticulumPlasma membraneCytoplasmRelease calciumionsTransverse tubule 12. Skeletal muscle is striated i.e. has visiblebandingStriations =bandsNucleiConnectivetissueseparates cellsMyofibrils fill sarcoplasmNucleusStriations SarcolemmaMyofibril 13. Myofibrils:are bundles of myofilamentsseparated by sarcoplasmic reticulumcontractile organelles of skeletal muscle extend the entire length of a muscle fibre [6-25 cmlong] 14. Myofilaments :MYOSIN thick filamentsACTIN thin filamentsSarcomereSarcomere: distance between two Z-lines 15. Sarcomeres are:repeating units of equal length in amyofibril the units of contraction 16. Sarcomeres are made of overlapping actin &myosin filamentsA band dArkI band - lIghtThick and thin filaments overlapeach other in a pattern thatcreates striations. 17. Two bands in the SarcomereActin Actin + myosin ActinI band A band I bandMyosinZ line H zone Z lineSARCOMEREActinRegion ofoverlapMyosincross-bridge 18. Learn to draw sarcomere structureSyllabus says: M line, but some books call it M band 19. The structure of Skeletal MuscleM lineA bands - made of actin and myosinI bands - made solely of actin filaments 20. A Sarcomere 21. How will a TS through the I band look like? 22. Proteins required for muscle contraction:1. Actin2. Myosin3. Troponin4. Tropomyosin 23. Each actin filament is made up of:two helical strands ofglobular actin molecules(G-actin) which twistround each anotherG-actinThe whole assembly ofactin molecules is calledF-actin (fibrous actin).F-actin 24. Tropomyosin:- forms a fibrous strand around the actinfilament 25. Troponin : a globular protein vital tocontraction of muscle fibreTroponin has three subunits:one to bind:1.Actin2. Tropomyosin3. Ca2+ 26. Tropomyosin covers sites where actinbinds to myosin 27. The Myosin molecule consists of two longpolypeptide chains coiled together :each chain ends ina globular head[cross bridge]Tail(a) A myosin molecule 28. The Myosin Heads have two sites:ATPase sitebinds &hydrolyses ATPActin-binding sitemyosin binds toactin, forming across-bridgeTropomysoin 29. Myosin head changes position 30. The Sliding Filament Theory of MuscleContraction: actin slides past myosin 31. Skeletal Muscle Contraction 32. The Sliding Filament Theory of Muscle Contractionsarcomeres shorten and so myofibrilshortensin turn, the muscle fibre shortens 33. What happens to the size of actin &myosin as they slide?Do not change in length 34. What happens to the size of :A band - Remains the sameShortensShortensI band -H zone - 35. Micrographs showing sarcomere contractionThe light (I) bands become shorterRelaxedmuscleContractedmusclerelaxed sarcomerecontracted sarcomereThe dark bands (A) bands stay thesame length 36. The Sliding Filament Theory of MuscleContraction Myosin cross-bridgespull on thin filaments. Thin filaments slideinward. Z lines come towardeach other. Sarcomeres shorten.The muscle fibershortens. The muscleshortens.Figure 6.7 37. The Neuromuscular Junction 38. A Motor Unit is made up of: all the fibres activated by a single motor neurone all the fibres contract simultaneously 39. Number of Motor Units involved varies 40. Ca2+ ions needed forcontraction arereleased from: 41. Depolarisation travels along T-tubules 42. Closer look at T-Tubules 43. Sliding FilamentModelActin cross-bridgesto myosin.Actin slides pastmyosin in a shortpower stroke.Cross-bridge isbroken. Head iscocked.Another cross-bridgeforms.Another power stroke slides actincloser to centre of sarcomere. 44. Details of Sliding Filament Theorystart 45. Remember that when:Myosin binds ATP:cross-bridge isdisconnectedATP is hydrolysed:myosin head isrepositioned able toform another cross-bridge1 212 46. Cross-bridge formation occurs in the presence ofCa 2+ 47. What happens if Ca2+ levels are:Low:tropomyosin inhibitscross-bridge formationHigh: Ca2+ binds to troponin tropomyosin isdisplaced, allowingthe formation ofactin-myosin cross-bridges 48. How is the cross-bridge broken?The myosin head binds a molecule of ATP,which causes it to release the actin 49. What happens in the absence of ATP? the actin-myosin bondscannot be broken the muscles stiffenThis explains why muscles stiffensoon after animals die, acondition known asRIGOR MORTIS 50. Do the muscles remain stiff forever in adead animal?NOEventually the proteins begin to losetheir integrity, and the muscles soften.Dead !! 51. Question: [MAY, 2000]This question concerns muscle.a) Distinguish between sarcomeres andmyofibrils. (2)Sarcomeres are the units of contraction. Theylie between two Z-lines.Myofibrils are bundles of myofilaments madeof actin and myosin. 52. Question: [MAY, 2000]b) Briefly explain the role of actin and myosin incontraction of striated muscle. (4)When calcium ions bind to troponin, myosin-bindingsites on actin filaments are exposed and myosinheads bind to actin, releasing ADP.The myosin head changes position and filamentsslide past each other.ATP binds to myosin, causing it to release actin.Hydrolysis of ATP makes the myosin head return tooriginal position. 53. Question: [MAY, 2000]c) What role is played by the Z line (or Z disc)during the contraction of striated muscle fibres?Z-lines hold actin filaments together. Distancebetween Zlines shortens on contraction. (2)d)The presence of calcium ions is necessary for thehydrolysis of ATP. How would removal of calciumions from the muscle fibre sarcoplasm affectcontraction? (2)Contraction stops. ATP is needed to break thecross-bridges between myosin and actin. 54. SummaryNAME FUNCTIONActinfilamentsSlide past myosin, causingcontractionCa2+ Needed for myosin to bindto actinMyosinfilamentsPull actin filaments bymeans of cross-bridges; areenzymatic and split ATPATPSupplies energy for musclecontraction 55. Energy Supply for Contraction:Glucose: is usually the source of energy for musclecontraction Phosphocreatine: is a PHOSPHAGEN a high energy phosphatecompound which acts as a reservoir ofphosphate-bond energy in the cell 56. Fig. 12 Glycogen stores in muscle 57. Question: [SEP, 2001]The figure is an electron micrograph of mammalian muscletissue.a) What type of muscle tissue is shown in the figure? (1)skeletal / voluntary / striatedb) What name is given to the region delimited by thehorizontal arrows in the diagram? (1)Sarcomerec) Briefly describe the structure ofthis region. (2)Lies between two Z-lines.Consists of alternating thin actinand thick myosin filaments. 58. d)Give a brief outline of the role of actin, myosinand ATP in the functioning of this type ofmuscle. (3)When calcium ions bind to troponin, myosin-bindingsites on actin filaments are exposed andmyosin heads bind to actin, releasing ADP.The myosin head changes position and filamentsslide past each other.ATP binds to myosin, causing it to release actin.Hydrolysis of ATP makes the myosin head returnto original position. 59. Question: [SEP, 2011]This question concerns skeletal muscle in the humanbody.a)What is muscle? (1)A muscle is a contractile tissue of animals.b) Briefly describe the gross structure of skeletal muscle.(2)Skeletal muscle is composed of bundles of musclefibres. A muscle fibre is a muscle cell which iscomposed of myofibrils. Myofibrils are composed ofmyofilaments. 60. Question: [SEP, 2011]c)Why is skeletal muscle striated? (3)The striations are bands seen under themicroscope.There are dark and light bands whichalternate.The bands consist of alternating thin actin andthick myosin filaments organised within thesarcomere. 61. Question: [SEP, 2011]d) Draw a diagrammatic representation of asingle sarcomere in the space below. (2) 62. Essay Titles1.Write an account on The role of proteins inanimal locomotion. [MAY, 2005]2.Describe the fine structure of vertebrateskeletal muscle and review the mechanismthrough which skeletal muscle contracts.[MAY, 2009] 63. OVERVIEWA) TYPES OF MUSCLESB) STRIATED MUSCLEC) HYDROSTATIC SKELETONS,EXOSKELETONS AND ENDOSKELETONSD) THE VERTEBRAL COLUMN 64. Muscles can onlycontract and relax.Without somethingrigid to pull against, amuscle would just be aformless mass. 65. Skeletal systems provide rigid support againstwhich muscles can pull, creating directedmovements.Look at the flashes of redwhen the legs walkforward. These are theworking muscles as theycontract;the muscles in yellow areat rest 66. Three types of skeletons in animals:1. Hydrostatic2. Exoskeletons3. Endoskeletons 67. Hydrostatic skeleton / hydroske