Muscle Contraction Can Occur When

Question

Muscle contraction can occur when:
A)myosin filaments shorten.
B)I bands remain unchanged.
C)sarcomeres shorten.
D)A bands lengthen.

Accepted Answer

Muscle contraction occurs when the sarcomeres, the basic functional units of muscles, shorten. This shortening results from the movement of the actin filaments towards the center of the sarcomere, which is facilitated by the sliding of myosin filaments along the actin filaments. During contraction, the I bands and H zones (which represent areas of the sarcomere that contain only actin or only myosin filaments, respectively) reduce in size, while the A bands (which represent the length of the myosin filaments) stay the same. Therefore, choices A, B, and D are incorrect.