The fight or flight response is a complicated systemic reaction. These are just some of the instantaneous
messengers and physiologic changes involved.
In fact, the initial perception of a threat or danger is also received by an area in the brain stem that begins
yet another axis of communication and response involving the release of the messenger norepinephrine. Like
cortisol and epinephrine, norepinephrine travels throughout the body, triggering cell signaling cascades in a number of cell types.
Regardless of their kind, or point of origin, cell signaling molecules involved in the fight or flight response work closely together.
Their overall effect is an increase in circulation and energy to certain body systems and a downshift of less important ones into
maintenance mode. In this way, the fight or flight response prepares the body for extreme action.