So we can close off these gap junctions by either increasing the concentration of the calcium, increasing the concentration of the h plus ions. So the same thing as saying lowering the PH number three is there are special hormones that can basically induce the process of phosphorylation of these gap junctions. And that too can close off the gap junction. And number four is in some cases, changing the voltage difference can also actually close off these gap junctions. Now, why would we want to actually close off a gap junction? Well, let's suppose we have two cells which are connected by these gap junctions, and one of the cells is damaged in some way and ends up dying.