Which region is the lighter area in the midsection of the dark A band where filaments do not overlap?

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Study for the Ivy Tech APHY 101 Muscle System Test. Dive into comprehensive questions with clear hints and explanations, boosting your confidence for the exam!

Multiple Choice

Which region is the lighter area in the midsection of the dark A band where filaments do not overlap?

Explanation:
In a sarcomere, the A band marks the length of the thick (myosin) filaments and includes areas where thin (actin) filaments overlap them. The lighter region in the middle of that dark A band is where there is no overlap between thick and thin filaments—the H zone. Since actin isn’t present to overlap with myosin there, this area looks lighter under a light microscope. The I band is the lighter region outside the A band that contains only actin, and the Z disc marks the boundaries between sarcomeres. So the described lighter midsection without filament overlap is the H zone.

In a sarcomere, the A band marks the length of the thick (myosin) filaments and includes areas where thin (actin) filaments overlap them. The lighter region in the middle of that dark A band is where there is no overlap between thick and thin filaments—the H zone. Since actin isn’t present to overlap with myosin there, this area looks lighter under a light microscope. The I band is the lighter region outside the A band that contains only actin, and the Z disc marks the boundaries between sarcomeres. So the described lighter midsection without filament overlap is the H zone.

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