Which statement concerning Z lines is correct?

Question

Quizplus · Accepted Answer

Z lines are structures found in striated muscle fibers that mark the boundaries of sarcomeres. They are located at the ends of the sarcomere and extend down the middle of the I band.

Answer: D 
 Thin filaments are composed of actin and are found in the I band of the sarcomere. Z lines attach to the ends of thin filaments and help to anchor them in place. Therefore, Z lines are not the thin filaments themselves.

Choice A is incorrect as T tubules are invaginations of the plasma membrane found in skeletal and cardiac muscle fibers that help to propagate action potentials.

Choice C is incorrect as cross bridges are formed by myosin, a protein found in thick filaments within the sarcomere.

Which Statement Concerning Z Lines Is Correct