Explain why sarcomere tension increases as the sarcomere length shortens from an extended length of 3.5 ?m to 2 ?m but then decreases if the sarcomere contracts to a length of 1.5 ?m
What will be an ideal response?
Answer: At the extended length, some myosin heads on each end of the bipolar filaments are not overlapping with actin thin filaments and therefore cannot generate force. As the sarcomere shortens, more of the myosin heads overlap with thin filaments and add to the force generated. At a sarcomere length of 2 μm, all of the myosin heads are positioned to interact with the thin filaments and maximal force is generated. Further sarcomere shortening causes the ends of actin thin filaments from one half sarcomere to interfere with myosin crossbridge formation in the other half sarcomere, decreasing the number of force-producing crossbridges and sarcomere tension.
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