Which structure marks the boundary between adjacent sarcomeres?

Which structure marks the boundary between adjacent sarcomeres?

• A. Z Disc
• B. M Line
• C. A Band
• D. I Band

Answer: (A)

The boundary between adjacent sarcomeres is marked by the Z-disc (Z-line). This structure anchors the thin actin filaments from each sarcomere and aligns them within the myofibril, effectively defining the start of one sarcomere and the end of the previous one. The sarcomere stretches from one Z-disc to the next, so when you contract, the Z-discs move closer together as the thin filaments slide inward, shortening the sarcomere. The M-line sits at the center of the sarcomere and stabilizes the thick filaments, while the A-band and I-band describe regions related to filament length and arrangement but do not define the boundaries between sarcomeres.

The boundary between adjacent sarcomeres is marked by the Z-disc (Z-line). This structure anchors the thin actin filaments from each sarcomere and aligns them within the myofibril, effectively defining the start of one sarcomere and the end of the previous one. The sarcomere stretches from one Z-disc to the next, so when you contract, the Z-discs move closer together as the thin filaments slide inward, shortening the sarcomere. The M-line sits at the center of the sarcomere and stabilizes the thick filaments, while the A-band and I-band describe regions related to filament length and arrangement but do not define the boundaries between sarcomeres.