Question

how can you make our cardiac muscles work harder

Answer 1

calcium ions are generally present inside the smooth endoplasmic reticulum (ser) of cardiac cells.

so, ser releases out calcium ions into the cytosol through voltage gated ion channels whenever needed that too in very little amounts.

now the calcium ions have to be sent out of the cardiac cell through antipoter transport mechanism where na+ moves inside cardiac cells and ca2+ ions moves out generating energy to perform contraction and relaxation.