But when epinephrine, which is, by the way, a tyrosine based hormone, when epinephrine actually binds onto the alpha adrenergic receptor, what it does is initiates the phosphonosatide cascade. And what that cascade actually does is it basically stimulates the release of calcium ions that are stored inside the lumen of the endoplasm reticulum of these liver cells. And so we have the influx of these calcium ions into the cytoplasm of the liver cell. And remember from our discussion on phosphoralase kinase that the calcium ions actually bind onto the delta units of phosphorace kinase. And so on top of phosphorelating the phosphorylase kinase to actually activate this enzyme the calcium ions also have to bind to the phosphorylase kinase. So we see that Glucagon actually stimulates PKA to phosphorylate the phosphorylase kinase while the epinephrine helps release the calcium ions which are also needed to actually activate the phosphorylase kinase.