This increase in Na+ in the sarcolemma, reduces the Na+ gradient exploited by sodium-calcium exchanger (NCX), and stops them from working effectively. Ca2+ ions accumulate inside the sarcolemma as a result, and are taken up by sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) pumps.
This increase in Na+ within the sarcolemma impairs the sodium-calcium exchanger's ability to function properly, resulting in an accumulation of Ca2+ ions inside the sarcolemma and their subsequent uptake by SERCA pumps.