The fight-or-flight response, also known as the acute stress response, refers to a physiological reaction that occurs in the presence of something that is terrifying, either mentally or physically. The fight-or-flight response was first described in the 1920s by American physiologist Walter Cannon. Cannon realised that a chain of rapidly occurring reactions inside the body help mobilise the body’s resources to deal with threatening circumstances.

In response to acute stress, the body’s sympathetic nervous system is activated due to the sudden release of hormones.The sympathetic nervous systems stimulates the adrenal glands triggering the release of catecholamines, which include adrenaline and noradrenaline. This results in an increase in heart rate, blood pressure and breathing rate. After the threat is gone, it takes between 20 to 60 minutes for the body to return to its pre-arousal levels.

The fight-or-flight response is also known as the acute stress response. Essentially, the response prepares the body to either fight or flee the threat. It is also important to note that the response can be triggered due to both real and imaginary threats.