when muscle contract. H, I zone or band contract. but waht about z lines? i think it's just a line right? so no change...but kbb..said z also contract... who's wrong?
muscle contraction
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The Z lines get closer together as the sarcomere contracts.
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that's correct, the Z lines just define the sacromere. If you mean sacromere by stating Z lines, then you are correct. Only the H zone, I band, and sacromere (from one Z line to the other Z line) contract.
Hope that helps.
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The z lines wouldn't contract, they are the definition of a sacromere unit, perhaps they mean the sarcomere unit itself contracts, then that is true, z lines don't do anything but anchor the actin filaments and serve as boundary markers.
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not sure what you're getting at...but to clear up any confusion that onlookers may be seeing.
z lines define sarcomere borders. when muscle contracts actin/myosin interactions pull the z lines together thus the distance between them gets smaller.
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It's actually pretty simplistic. The I-band and H-zone refer to a REGION which is contracts (gets smaller) when the muscle contracts. The z-lines anchor the microfilaments, and while they do not contract (bec they're not a region), the distance between each z-line (that defines the sarcomere, as pointed out) will become smaller. . .
