Calcium is a crucial part of muscle contraction. The ionic element is released from muscles during contraction and relaxation. The release of calcium helps propagate the muscle contraction and relaxation stages.
Action potentials are electrical signals that tell muscle tissue to contract. As an action potential reaches a muscle cell, it triggers calcium to release from the sarcoplasmic reticulum of the cells. The calcium ions then flow into the cytoplasm and bind to the troponin and tropomyosin molecules in the actin filaments of the muscle cells. The binding of calcium allows the troponin to change shape and expose the actin-myosin binding site. Myosin then connects to actin, and the formed complex forms a cross bridge that opens and closes and allows the muscle cells to contract. After the contraction and action potential is over, the calcium channels close, and calcium is removed from the muscle cells.