how does calcium work in smooth muscle
During contraction, the smooth-muscle cell's intermediate filaments help to draw the cell up, like closing a drawstring purse. Calcium ions regulate contraction in smooth muscle, but they do it in a slightly different way than in skeletal muscle: 1  Calcium ions come from outside of the cell.2  Calcium ions bind to an enzyme complex on myosin, called calmodulin-myosin light chain kinase. Calcium ions come from outside of the cell. 2  Calcium ions bind to an enzyme complex on myosin, called calmodulin-myosin light chain kinase. 3  The enzyme complex breaks up ATP into ADP and transfers the P i directly to myosin. 4  This P i transfer activates myosin.