Stress is a _______1______ ________2_______. When danger appears, it can get you out of trouble quickly. Your body ______3________ up the ______4_________ and _______5_________ all its _______6_________ into getting you _____7__________. Your heart _______8__________ ______9________ to increase ______10___________ ______11__________. _________12____________ is sent to the muscles as ______13____________ ________14_________. And you become totally _____15__________ on what psychologists call: fight-or-flight.