MICROANATOMY

Detailed explanation-1: -1 Tropomyosin. TM regulates smooth muscle contraction by blocking the myosin binding sites on actin, preventing actin–myosin interaction.

Detailed explanation-2: -Tropomyosin filaments wrap around actin, sterically blocking myosin from binding to actin.

Detailed explanation-3: -When the concentration of Ca2+ is low, the complex of the troponins with tropomyosin blocks the interaction of actin and myosin, so the muscle does not contract. At high concentrations, Ca2+ binding to troponin C shifts the position of the complex, relieving this inhibition and allowing contraction to proceed.

Detailed explanation-4: -Tropomyosin binds to troponin to form a troponin-tropomyosin complex. The troponin-tropomyosin complex prevents the myosin “heads” from binding to the active sites on the actin microfilaments. Troponin also has a binding site for Ca++ ions.