Which of These Statements Describes Z Lines

Question

Which of these statements describes Z lines
A)They are formed by T tubules.
B)They extend down the middle of the I band.
C)They are formed by cross bridges.
D)They are filaments.

Accepted Answer

Z lines are found in the middle of the I band and mark the boundary between adjacent sarcomeres. They are made up of specialized proteins and help anchor the actin filaments within the sarcomere. T tubules are invaginations of the sarcolemma that help transmit the action potential deep into the muscle fiber. Cross bridges are connections between myosin and actin filaments that allow for muscle contraction. Filaments refer to the actin and myosin proteins that make up the bulk of the muscle fiber.