the long term regulation of the cytosolic ionized ca is the consequence of two separate ca transport mechanisms present in most eucaryotic cells : a high-affinity and low-capacity system which is in charge of extruding ca during resting conditions ( the ca pump ) and a low affinity and high-capacity system ( na/ca exchange ) designed not only to extrude ca2+ ions when the cai raises above certain levels , but also to led ca into the cell under conditions that favor the reverse reaction of the exchange , such as increase in nai , decrease in external na and membrane depolarization .
C1383501
cytosolic
C0007634
cell