The Skeletal System and Skin

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The Skeletal System and Skin. Endoskeletons Exoskeletons Hydrostatic skeletons Bone Osteocytes Osteoclasts Osteoblasts Restructuring of bone. Collagen Phosphate Calcium hydroxyapatite. Compact Bone Spongy Bone Red bone marrow Yellow bone marrow Blood vessels Haversian canals - PowerPoint PPT Presentation

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Lecture #21 Date ____The Skeletal System and SkinThe Skeletal SystemEndoskeletonsExoskeletonsHydrostatic skeletonsBoneOsteocytesOsteoclastsOsteoblastsRestructuring of bone.CollagenPhosphateCalciumhydroxyapatiteCompact BoneSpongy BoneRed bone marrowYellow bone marrowBlood vesselsHaversian canalsCanaliculilamallaeLong Bone StructurePeriosteumMedullary or Marrow CavityEpiphyseal or Growth plate (composed of cartilage)Articular cartilageAxial and Appendicular SkeletonAxial SkeletonSkullVertebral columnVertebrae (33 bones)Cartilaginous disksCervical, Thoracic, Lumbar, sacrum, coccyxRib cage (24 ribs)SternumAppendicular SkeletonAll bones not part of the axial skeleton.AppendagesJointsArticulationArticular cartilageLigamentsHinge jointBall and socket jointsSynovial cavities and fluidBursameniscusCartilageWhere found?ChondrocytesLacunaeHyaline cartilageFlexibleLight weightThe skinIntegumentFunctionsEpidermisDermisHypodermisEpidermisKeratinDead, flat squamous cells.Airtight and watertightMelanincuticileDermisDense connective tissueBlood vesselsMaintenance of body temperatureNerve fibersSmooth muscleElastic fibersFollicles (hairs)Sebaceous glandsDermis and HypodermisArrector pili musclesGoose bumpsReceptorsNervesSweet GlandsExocrine glandsHypodermisSubcutaneous LayerAdipose or fatLoose connective tissueLots of major blood vessels.Sensory and Motor Mechanisms(Just focusing on motor mechanisms)Motor MechanismsMuscle voluntary, striatedinvoluntary, striatedauto-rhythmicinvoluntary, non-striatedevolved firstmulti-nucleateddigestive systemarteries, veinsheartmoves bone26All cells have a fine network of actin and myosin fibers that contribute to cellular movement. But only muscle cells have them in such great abundance and far more organized for contraction. SMOOTH MUSCLESmooth muscle was the first to evolve. Lining of blood vessels, wall of the gut, iris of the eye.Some contract only when stimulated by nerve impulse. Others generate electrical impulses spontaneously and then are regulated by nervous system.CARDIAC MUSCLESmall interconnected cell with only one nucleus. Interconnected through gap junctions. Single functioning unit that contract in unison via this intercellular communication. Mostly generate electrical impulses spontaneously. Regulated rather than initial stimulation by nervous system.SKELETAL MUSCLEFusion of many cells so multi-nucleated. Attached by tendon to bone. Long thin cells called muscle fibers.tendonskeletal musclemuscle fiber (cell)myofilamentsmyofibrilsplasma membranenucleiOrganization of Skeletal muscle27Human endoskeleton206 bones28Muscles movement Muscles do work by contractingskeletal muscles come in antagonistic pairsflexor vs. extensorcontracting = shorteningmove skeletal partstendonsconnect bone to muscleligamentsconnect bone to bone2930Structure of striated skeletal muscle Muscle Fibermuscle celldivided into sections = sarcomeresSarcomerefunctional unit of muscle contraction alternating bands of thin (actin) & thick (myosin) protein filaments31Muscle filaments & Sarcomere Interacting proteinsthin filamentsbraided strands actintropomyosintroponinthick filamentsmyosin32Thin filaments: actinComplex of proteinsbraid of actin molecules & tropomyosin fiberstropomyosin fibers secured with troponin molecules33Thick filaments: myosinSingle proteinmyosin moleculelong protein with globular headbundle of myosin proteins:globular heads aligned34Interaction of thick & thin filamentsCross bridges connections formed between myosin heads (thick filaments) & actin (thin filaments) cause the muscle to shorten (contract) sarcomeresarcomere35Where is ATP needed?3412111Cleaving ATP ADP allows myosin head to bind to actin filamentthin filament(actin)thick filament(myosin)ATPmyosin headformcrossbridgebinding siteSo thats where those10,000,000 ATPs go!Well, not all of it!ADPreleasecrossbridgeshortensarcomere136Closer look at muscle cellmulti-nucleatedMitochondrionSarcoplasmicreticulumTransverse tubules(T-tubules)37Muscle cell organellesSarcoplasm muscle cell cytoplasmcontains many mitochondriaSarcoplasmic reticulum (SR)organelle similar to ERnetwork of tubesstores Ca2+Ca2+ released from SR through channelsCa2+ restored to SR by Ca2+ pumpspump Ca2+ from cytosolpumps use ATPCa2+ ATPase of SRATPTheresthe restof theATPs!But whatdoes theCa2+ do?38Muscle at restInteracting proteinsat rest, troponin molecules hold tropomyosin fibers so that they cover the myosin-binding sites on actintroponin has Ca2+ binding sites39The Trigger: motor neurons Motor neuron triggers muscle contractionrelease acetylcholine (Ach) neurotransmitter40At rest, tropomyosin blocks myosin-binding sites on actinsecured by troponinCa2+ binds to troponinshape change causes movement of troponinreleasing tropomyosinexposes myosin-binding sites on actinCa2+ triggers muscle action41How Ca2+ controls muscleSliding filament modelexposed actin binds to myosinfibers slide past each otherratchet systemshorten muscle cellmuscle contractionmuscle doesnt relax until Ca2+ is pumped back into SR requires ATPATPATP42Put it all together1ATP234576ATP43How it all worksAction potential causes Ca2+ release from SRCa2+ binds to troponinTroponin moves tropomyosin uncovering myosin binding site on actinMyosin binds actinuses ATP to "ratchet" each timereleases, "unratchets" & binds to next actinMyosin pulls actin chain alongSarcomere shortens Z discs move closer togetherWhole fiber shortens contraction!Ca2+ pumps restore Ca2+ to SR relaxation!pumps use ATPATPATP44Fast twitch & slow twitch musclesSlow twitch muscle fiberscontract slowly, but keep going for a long timemore mitochondria for aerobic respiration less SR Ca2+ remains in cytosol longerlong distance runnerdark meat = more blood vessels Fast twitch muscle fiberscontract quickly, but get tired rapidlystore more glycogen for anaerobic respiration sprinterwhite meat45Muscle limitsMuscle fatiguelack of sugarlack of ATP to restore Ca2+ gradientlow O2lactic acid drops pH which interferes with protein functionsynaptic fatigueloss of acetylcholineMuscle crampsbuild up of lactic acid ATP depletionion imbalancemassage or stretching increases circulation46Diseases of Muscle tissueALSamyotrophic lateral sclerosisLou Gehrigs diseasemotor neurons degenerateMyasthenia gravisauto-immuneantibodies to acetylcholine receptorsStephen Hawking47BotoxBacteria Clostridium botulinum toxinblocks release of acetylcholinebotulism can be fatalmuscle48Rigor mortisSo why are dead people stiffs?no life, no breathingno breathing, no O2no O2, no aerobic respirationno aerobic respiration, no ATPno ATP, no Ca2+ pumpsCa2+ stays in muscle cytoplasmmuscle fibers continually contracttetany or rigor mortiseventually tissues breakdown& relaxmeasure of time of death492006-2007So dont be a stiff!Ask Questions!!50

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