Interaction of thick & thin filaments __________________ –_____________________________________ _____________________________________ –_____________________________________

Embed Size (px)

Text of Interaction of thick & thin filaments __________________ –_____________________________________...

Slide 1

Interaction of thick & thin filaments__________________ __________________________________________________________________________ _____________________________________

sarcomeresarcomere1

Where is ATP needed?

3412111Cleaving ATP ADP allows myosin head to bind to actin filamentthin filament(actin)thick filament(myosin)ATPmyosin headbinding site

So thats where those10,000,000 ATPs go!Well, not all of it!ADPformcrossbridgereleasecrossbridgeshortensarcomere12Closer look at muscle cell

multi-nucleatedMitochondrionSarcoplasmicreticulumTransverse tubules(T-tubules)3

Muscle cell organelles_________________________ muscle cell cytoplasmcontains many mitochondria_________________________organelle similar to ERnetwork of tubes_________________Ca2+ released from SR through channelsCa2+ restored to SR by Ca2+ pumpspump Ca2+ from cytosolpumps use ATPCa2+ ATPase of SRATP

The restof theATPs!But whatdoes theCa2+ do?4Muscle at restInteracting proteinsat rest, ________ molecules hold _____________ fibers so that they cover the myosin-binding sites on actintroponin has Ca2+ binding sites

5The Trigger: motor neurons

Motor neuron triggers muscle contractionrelease ______________ (Ach) neurotransmitter6Nerve signal travels down ___________stimulates sarcoplasmic reticulum (SR) of muscle cell to ________________ flooding muscle fibers with Ca2+ Nerve trigger of muscle action

7At rest, tropomyosin _______ myosin-binding sites on actinsecured by troponinCa2+ binds to _______________________ causes movement of troponinreleasing tropomyosin_____________________________ on actinCa2+ triggers muscle action

8Coupling Excitation to Contraction

1. Ca2+ ____ action potentials to contraction.

2. At rest, Ca2+ is stored in the __________.

3. Spaced along the plasma membrane (_____________) of the muscle fiber are inpocketings of the membrane that form ________ of the __________". These tubules plunge repeatedly into the interior of the fiber.

4.The tubules of the T system terminate near the ___________________ of the sarcoplasmic reticulum.

5. Each action potential created at the neuromuscular junction sweeps quickly along the sarcolemma and is carried into the T system.

How Ca2+ controls muscle__________________exposed actin binds to myosinfibers slide past each otherratchet systemshorten muscle cellmuscle contractionmuscle doesnt relax until Ca2+ is pumped back into SR requires ATP

ATPATP10

Fig. 50-27-4ThinfilamentsATP Myosin head (low-energy configurationThick filamentThin filamentThickfilamentActinMyosin head (high-energy configurationMyosin binding sitesADPP iCross-bridgeADPP iMyosin head (low-energy configurationThin filament movestoward center of sarcomere.ATP ADPP i+11

Fig. 50-28Myosin-binding siteTropomyosin(a) Myosin-binding sites blocked(b) Myosin-binding sites exposedCa2+Ca2+-binding sitesTroponin complexActin__________ concentration: muscle contracts________ concentration: binding sites are covered and contraction stopsRole of Ca andRegulatory Proteins12

Put it all together1ATP234576ATP13How it all worksAction potential causes ______ release from SRCa2+ binds to ______________Troponin moves ____________ uncovering ___________________ on actinMyosin binds ______uses ____ to "ratchet" each timereleases, "unratchets" & binds to next actinMyosin pulls actin chain alongSarcomere _________Z discs move closer togetherWhole fiber shortens _____________!Ca2+ pumps restore Ca2+ to SR ___________!pumps use _____ATPATP14

Fig. 50-26ZRelaxedmuscleM Z Fully contractedmuscleContractingmuscleSarcomere0.5 mContractedSarcomere15