Multiple Choice
What happens to the I band when the sarcomere contracts during muscle contraction?
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9. Muscle Tissue
Sliding Filament Theory and the Sacromere
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In the context of sliding filament theory, what structural feature causes skeletal muscle fibers to appear striated under the microscope?
A
The circular arrangement of myofilaments around a central lumen, producing alternating light and dark rings
B
Randomly oriented actin and myosin filaments distributed uniformly throughout the cytoplasm
C
The presence of intercalated discs that connect adjacent muscle cells
D
The repeating arrangement of thick (myosin) and thin (actin) filaments into sarcomeres, creating alternating A bands and I bands
Verified step by step guidance1
Understand that the striated appearance of skeletal muscle fibers is due to the organized arrangement of contractile proteins within the muscle cells.
Recognize that skeletal muscle fibers contain repeating units called sarcomeres, which are the functional contractile units.
Know that each sarcomere is composed of thick filaments (myosin) and thin filaments (actin) arranged in a precise, repeating pattern.
Identify that the alternating dark and light bands seen under the microscope correspond to the A bands (where thick filaments are present) and I bands (where only thin filaments are present).
Conclude that this regular, repeating arrangement of thick and thin filaments within sarcomeres causes the characteristic striated pattern observed in skeletal muscle fibers.
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