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.
An increase in Na+ within the sarcolemma disrupts the sodium-calcium exchanger's function, preventing it from working efficiently. This leads to a buildup of Ca2+ ions inside the sarcolemma, which are then pumped into the sarcoplasmic reticulum by SERCA.