ANATOMY

Detailed explanation-1: -Troponin, which regulates the tropomyosin, is activated by calcium, which is kept at extremely low concentrations in the sarcoplasm. If present, calcium ions bind to troponin, causing conformational changes in troponin that allow tropomyosin to move away from the myosin-binding sites on actin.

Detailed explanation-2: -Upon binding calcium, troponin moves tropomyosin away from the myosin-binding sites on actin (bottom), effectively unblocking it.

Detailed explanation-3: -Troponin C (TnC; 18 kDa) is the calcium-binding component of the contractile apparatus and upon binding intracellular Ca2 + ions induces a conformational change in the troponin–tropomyosin complex, reducing TnI inhibition of the actinomysin ATPase and allowing muscle contraction to occur [18].

Detailed explanation-4: -Tropomyosin covers the actin-binding sites, preventing myosin from forming cross-bridges while in a resting state; troponin binds to tropomyosin and helps to position it on the actin molecule.