The fight-or-flight response (or acute stress response) is a set of physiological changes that occur when an animal is threatened.[1] The changes include increased heart rate, breathing rate and blood pressure.
This response was first described by W.B Cannon.[2] He found that animals react to threats with a general discharge of the sympathetic nervous system. This leads to changes such as those mentioned above. The changes prepare the animal for fighting or fleeing.[3] This response is the first stage of a general adaptation that regulates stress responses among vertebrates and other organisms.[4]