Anything perceived as a threat trips the amygdala-the brain's hand-wringing sentry-to set in motion the biochemical cascade known as the fight-or-flight response. Bruce Siddle, who consults in this area and sits on the board of Strategic Operations, prefers the term "survival stress response." Whatever you wish to call it, here is a nice, concise summary, courtesy of Siddle: "You become fast, strong, and dumb." Our hardwired survival strategy evolved back when threats took the form of man-eating mammals, when hurling a rock superhumanly hard or climbing a tree superhumanly fast gave you the edge that might keep you alive. A burst of adrenaline prompts a cortisol dump to the bloodstream. The cortisol sends the lungs into overdrive to bring in more oxygen, and the heart rate doubles or triples to deliver it more swiftly. Meanwhile the liver spews glucose, more fuel for the feats at hand. To get the goods where the body assumes they're needed, blood vessels in the large muscles of the arms and legs dilate, while vessels serving lower-priority organs {the gut, for example, and the skin} constrict. The prefrontal cortex, a major blood guzzler, also gets rationed. Good-bye, reasoning and analysis. See you later, fine motor skills. None of that mattered much to early man. You don't need to weigh your options in the face of a snarling predator, and you don't have time.
( Mary Roach )
[ Grunt: The Curious Science of ]
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