Heres how it works in your body: You have a stress circuit that loops between your nervous system and your stress hormones called the hypothalamic-pituitary-adrenal (HPA) axis (see Figure 9.1). When youre faced with a major stressor, the hypothalamus releases a hormone called CRH, which then causes your pituitary gland to release another hormone called ACTH into your bloodstream. Thats the hormone that signals your adrenal glands to release the stress hormone cortisol, which in turn gets your adrenaline cranked up (adrenaline is the fight-or-flight hormone). All of this is fine and good for a while (the increased heart rate and blood pressure get you away from any predator), but if the stress doesnt stop, this flood of chemicals turns against youcompromising your immune system, exhausting your adrenal glands, throwing your cholesterol levels out of whack, and causing you to crave sugar and syrups that age you. And your prefrontal cortex, which, if you had listened to it, would have prevented you from getting into the problem in the first place, is bypassed again.