Chapter 1 Fight Flight or Freeze You stroll home from school kicking a pebble as you go At the corner by the coffee shop you absentmindedly step into the crosswalk and Danger Tires screech A horn blasts Before your brain has even formed the words city bus you've leaped out of the way You sprint the last few steps to the curb where you lean on your knees gasping Your whole body's shaking Your heart pounds your ears ring and all you can see is the afterimage of that big bus fender bearing down on you You've experienced something called the fight or flight response In its most basic form stress is your body's reaction to danger In a crisis you instinctively decide whether to fight or in this case run away Your reactions to an oncoming bus are exactly the same as your ancestors reactions to an encounter with a lion Our bodies have been practicing the emergency stress response for millions of years
X Ray Vision How did stress research begin With cat food In the early 1900s a Harvard Medical School professor named Walter Cannon was studying digestion He mixed cat food with a chemical dye then used X rays to trace the substance as it moved through kitty bellies Walter noticed something strange If a cat was upset or startled by a sudden noise all digestion stopped It seemed as if the cat's emotions were affecting its insides Walter shifted the entire focus of his research He began studying the way animals including humans react to sudden stimuli Over time he learned that when an animal is frightened the body stops spending energy on everyday things like digestion and shifts into an emergency response mode Walter wrote a book about the fight instinct and the flight instinct He suggested that when we're startled we instantly decide either to battle or to run Both reactions are triggered by fear and both affect many systems of the body Other researchers called Walter's discovery the fight or flight response And the science of stress was born Today scientists have added a third possible response to crisis freeze There are times when that saber toothed cat is a little too close We don't have time to run and we'll never win the fight So our brains tell us to do what a chameleon might freeze and hope to blend in with the trees
Pressure Players AMYGDALA Amygdalae which is the plural form of amygdala comes from the Greek word for almonds They're our almond shaped control pods The word stress itself was first used by physicists to describe pressure For example leaning against a fence puts stress on the wood In the 1920s a University of Montreal doctor named Hans Selye began using the word to describe the feelings of hospital patients No matter what was physically wrong with them they all seemed to be experiencing strain or pressure Like the wooden fence they were under stress Hans had other ideas too He noticed the fight or flight response could be triggered by good events as well as bad Imagine a group of people leaping from behind your living room couch and yelling Surprise Your hands fly into the air and your heart races For a second you feel like running away Your body is responding to stress even though a birthday party's usually a good thing Many of our fight or flight reflexes stem from the amygdalae two small regions near the base of the brain People often call this region the reptilian brain because it prompts some of our most basic drives and instincts In 2011 scientists in California wrote about a woman called S M They identified her by initials only for privacy reasons She had damaged her amygdalae twenty years before The scientists took S M into a pet store full of snakes and spiders They walked her through a haunted house then they showed her scary movies S M displayed no fear This helped prove to scientists that the amygdalae were definitely part of the brain's emergency response system During an intense situation the brain's big thinking center the prefrontal cortex gets overwhelmed And that's okay because a crisis is no time to ponder flowcharts or debate philosophies When our eyes or ears sense danger the brain passes that information directly to our amygdalae Jump first think later
What's Shaking Book Smarts Introducing the big boss your autonomic nervous system It takes care of all those things you don't think about like the beating of your heart and the wriggling of your intestines Like any big boss your autonomic nervous system has workers It puts two of them in charge of stress The first is the sympathetic nervous system manager of emergency responses When a bus looms or a tiger attacks the sympathetic nervous system makes instant changes It cues the adrenal glands near the kidneys to produce three stress hormones adrenaline norepinephrine and cortisol These chemicals take care of most of your fight or flight necessities When you get a blast of them here's what happens Though scientists didn't understand the fight or flight response until the early 1900s novelists have been describing it for ages The world's first known adventure novel Sinuhe was written in Egypt almost four thousand years ago In it the narrator says Confused by fear was my heart both my arms extended a shaking was falling on all my limbs That author didn't need science experiments to understand the effects of stress Your arms shoot up ready for defense Your heart races sending extra blood to your muscles and your brain and away from your digestive system as Walter Cannon discovered Your breathing speeds up so you get extra oxygen
