How Children Succeed: Grit, Curiosity, and the Hidden Power of Character

by Paul Tough

Our bodies regulate stress using a system called the HPA axis. HPA stands for “hypothalamic-pituitary-adrenal,” and that tongue-twisting phrase describes the way that chemical signals cascade through the brain and the body in reaction to intense situations. When a potential danger appears, the first line of defense is the hypothalamus, the region of the brain that controls unconscious biological processes like body temperature, hunger, and thirst. The hypothalamus emits a chemical that triggers receptors in the pituitary gland; the pituitary releases signaling hormones that stimulate the adrenal glands; and the adrenal glands then send out stress hormones called glucocorticoids that switch on a host of specific defensive responses. Some of these responses we can recognize in ourselves as they happen: emotions like fear and anxiety, and physical reactions like increased heart rate, clammy skin, and a dry mouth. But many effects of the HPA axis are less immediately apparent to us, even when we’re the ones experiencing them: neurotransmitters activate, glucose levels rise, the cardiovascular system sends blood to the muscles, and inflammatory proteins surge through the bloodstream.