During Contraction in a Skeletal Muscle Fiber

Question

During contraction in a skeletal muscle fiber:
A) the thick filaments meet at the center of the sarcomere.
B) the sarcomere length does not change.
C) actin and myosin molecules contract, causing filaments to shorten.
D) myosin cross-bridges (heads) move the thin filaments so that their ends meet or overlap in the center of the sarcomere.

Accepted Answer

During contraction in a skeletal muscle fiber, myosin cross-bridges (heads) attach to actin in the thin filaments and pull them towards the center of the sarcomere, causing the thin filaments to slide past the thick filaments. This sliding filament mechanism is responsible for muscle contraction. The sarcomere shortens, bringing Z lines closer together, but the filaments themselves do not change in length; instead, they slide past each other.