Superficial buffer barrier hypothesi

In addition to this function of controlling the overall cytosolic Ca " concentration adjacent to the myofilaments in the deep cytosol, there is evidence that the st also plays a role in controlling the influx of extracellular Ca -" through the plasmalemmal membrane. This has led to the independent proposal of two concepts - the superficial buffer barrier hypothesis and the capacita-tive model - both of which attempt to link sr function to extracellular Ca " influx. 

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