MICROANATOMY

Detailed explanation-1: -The Z-lines are pulled closer together during contraction and move further apart during relaxation. The Z-lines are closer during contraction because actin and myosin interaction generates cross-bridges, which slide the myofilaments over each other.

Detailed explanation-2: -Muscle contraction is driven by relative sliding between the thick and thin filaments, which in turn is driven by a cyclical interaction of the myosin heads with actin coupled to the hydrolysis of ATP.

Detailed explanation-3: -The area between two Z lines, a sarcomere, can be considered to be the primary structural and functional unit directly responsible for muscle contraction.…

Detailed explanation-4: -When (a) a sarcomere (b) contracts, the Z lines move closer together and the I band gets smaller. The A band stays the same width and, at full contraction, the thin filaments overlap.