Stress is a chain reaction. “When someone experiences a stressful event, the amygdala, an area of the brain that contributes to emotional processing, sends a distress signal to the hypothalamus,” Harvard Health Publications of Harvard Medical School explains. “This area of the brain functions like a command center, communicating with the rest of the body through the nervous system so that the person has the energy to fight or flee.”
This “fight-or-flight” response is responsible for the outward physical reactions most people associate with stress including increased heart rate, heightened senses, a deeper intake of oxygen and the rush of adrenaline. Finally, a hormone called cortisol is released, which helps to restore the energy lost in the response. When the stressful event is over, cortisol levels fall and the body returns to stasis.