MICROANATOMY

Detailed explanation-1: -When calcium binds to troponin, the troponin changes shape, removing tropomyosin from the binding sites. The sarcoplasmic reticulum stores calcium ions, which it releases when a muscle cell is stimulated; the calcium ions then enable the cross-bridge muscle contraction cycle.

Detailed explanation-2: -The calcium ion acts like a key to “unlock” troponin and move tropomyosin off of actin’s binding sites.

Detailed explanation-3: -This is done by binding to another structure, named troponin, inside the heart muscle cell. During relaxation, calcium has to be detached from troponin and expelled out of the cell or stored back inside the sarcoplasmic reticulum.

Detailed explanation-4: -Released calcium ions bind to the troponin complex (consisting of troponin I, troponin T, and troponin C) to change their conformation and result is contraction [146]. Contractile proteins (myosin and actin) and regulatory proteins (tropomyosin and troponin complex) are structural parts of the sarcomere.