PHYSIOLOGY
MICROSCOPIC MUSCLE ANATOMY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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I band
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A band
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H-Zone
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M-line
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Detailed explanation-1: -Cross-bridges can only form where thick and thin filaments overlap, allowing myosin to bind to actin.
Detailed explanation-2: -A bands (or anisotropic bands): It is also called the dark band and contains the whole thick filament (myosin). I bands (or isotropic bands): it is called the light band that contains only the thin filament (actin). The thin filament lies between the two thick filaments.
Detailed explanation-3: -Actin filaments, the thin filaments, are the major component of the I-band and extend into the A-band. Myosin filaments, the thick filaments, are bipolar and extend throughout the A-band. They are cross-linked at the centre by the M-band.
Detailed explanation-4: -The myosin and actin filaments overlap in peripheral regions of the A band, whereas a middle region (called the H zone) contains only myosin. The actin filaments are attached at their plus ends to the Z disc, which includes the crosslinking protein -actinin.