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A band
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The A band (anisotropic band) is the dark band of the sarcomere which contains the entirety of the myosin (thick) filaments and the parts of the actin (thin) filaments that overlap with the myosin filaments at either end. The slightly paler central region of the A band is called the H zone and does not contain actin filaments, thus appearing lighter than the rest of the A band where both myofilaments are overlapping. In the center of the A band is the M line, where myosin filaments are anchored.
The A band is the location where myofilament movement occurs during a muscle contraction. As the overlap of actin and myosin increases and the sarcomere shortens, it is the I band and H zone which narrow, while the width of the A band remains constant.
| Terminology |
English: A band Latin: Stria A |
| Definition | Dark band of the sarcomere containing the entirety of the myosin filaments and the overlapping parts of thin filaments |
| Function | Site of myofilament interaction responsible for a muscle contraction |
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