During muscle contraction, I. actin filaments cross the M line.
II. the Z lines move closer together.
III. myosin forms cross bridges with actin.
IV. actin and myosin coil around each other.

Question

Quizplus · Accepted Answer

During muscle contraction, actin filaments do not cross the M line. Instead, myosin forms cross bridges with actin, causing the actin filaments to slide past the myosin filaments, which results in the Z lines moving closer together. Actin and myosin do not coil around each other during contraction. Therefore, statements II and III are correct, but statement I and IV are incorrect. The best choice is B, which includes statement II and III but not I and IV.

During Muscle Contraction, I