And all these processes basically work together to carry out that specific physiological response. So effectors are molecules that are responsible for carrying out some type of cellular process that ultimately leads to that physiological response. And effectors can be transcription inducing molecules, enzymes. We have membrane pumps, we have membrane channels and so forth. So for instance, when we'll discuss insulin, we'll see that what insulin does is it increases the rate at which we update glucose molecules into the cell. And what that does is that means it influences the cells to produce many more of these protein molecules that can actually uptake the glucose molecules and that might involve the process of gene expression.