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234ff

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About 234ff

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  1. I am learning myology and encountered 2 problems in tetanus and summation: Unfused tetanus is just a continual summation of twitches if I am not mistaken. However, is it a MUST for summation / unfused tetanus to constantly increasing muscle tension from the photo (the graph) i.e. is this the definition? Since we are in unfused tetanus when we hold something, and I can’t feel my biceps are constantly increasing in contraction / tension. (to my understanding, complete tetanus is when we are lifting up very heavy things only as it utilizes too much ATP) Can I say the muscles are in tetanus during contracting (lifting), and also in tetanus during constantly contracted state (keep the thing holding up) Since tetanus is just a frequent action of sliding filaments, which is common in both actions? Also, during tetanus, I don’t need to shorten my muscles anymore (just holding something still), but myosin heads are still power-stroking to shorten the sarcomere/muscle, may I ask how to explain this? Thank you very much.
  2. (I am new to this forum so please tell me how to improve my questions) I am wondering what really powers the myosin head to undergo the power stroke to push the actin filaments towards the M-line. I have 2 thoughts: when ATP in the myosin head gets hydrolyzed, the energy released is stored in the head. This energy powers for the power stroke. when ATP is hydrolyzed, inorganic phosphate and ADP leave accordingly (90deg--> 50deg --> 45deg), the conformational changes of myosin head proteins cause the power stroke. I think (2) is more plausible as the order of actions (moving actin filaments by 6.7nm + 1.3nm in order) is more 'conventional'(wiki), rather than a single action (using energy by ATP hydrolysis, a 1-step boost of energy). However, if (2) is really correct, then may I ask what is the energy released in (1) used for in the myosin head, does it just simply fade away as heat energy? thank you very much :)
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