What is the role of Calcium during muscle contraction

VGCCs allow an influx of Calcium ions into cells across the plasma membrane by opening in response to an increase in membrane potential i.e. depolarisation Calcium is also released rapidly by intracellular stores Ca2+ inside the cell induces the release of more Ca2+ through ryanodine receptor channels ( RyR ) Calcium ions then bind to troponin to initiate contraction Relaxation occurs when Ca2+ unbinds from troponin Calcium is then pumped back into the sarcoplasmic reticulum for storage