As we have seen, in during epinephrine hormonal control or glucagon, dephosphorylated phosphorylase kinase is activated by being phosphorylated by protein kinase. This then activates stimulates glycogen degradation and phosphorylase.Furthermore, there is also another way to activate dephosphorylated phosphorylase kinase, at least partially, and which is by a high concentration of Ca2+ ions. This is very significant in muscle contraction which is triggered when Ca2+ is released from the internal store in the sarcoplasmic reticulum. Thus, as well as allosteric control and hormonal control during muscle contraction both of which stimulate glycogen degradation and there is also calcium control.