Question about actin-myosin complex (this is an offical aamcs guide question)

[mrh125]

which of the following would NOT change within a sacromere during skeletal muscle contraction?
A. the length of thick filaments
B. overlap between thick and thin filaments
C. the position of tropinin-tropomyosin complexes on the thin filaments
D. the positions at which the globular heads of the thick filaments bind to thin filaments

The answer is A, which really confuses me, I thought the myosin thick filaments were represented by the H-band and that the length of the h-band does change (decreases) during contraction. Can someone please explain why this is right?

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[Cmdr_Shepard]

The thick filaments are not the same as the H-bands. The H-bands decrease, yes, but the thick filament length doesn't change.

Have a look at this:

http://highered.mcgraw-hill.com/sit...apter10/animation__sarcomere_contraction.html