Paul Andersen explains how signal transmission is used to alter both cellular function and gene expression. He uses the example of epinephrine release in humans and how it is used in the fight or flight response. Epinephrine causes liver cells to release glucose that is normally stored as glycogen when they receive the signal of epinephrine. They are also able to create different enzymes when receiving this signal. The signal transduction pathway and the importance of CyclicAMP is included.