When the fight-or-flight response is caused by an immediate stressor, the response is useful and then subsides. What is this adaptation called?

Answer: Allostatis

Explanation: Fight-or-flight response is the nervous system's reaction to acute stressors and is characterized by the release of adrenaline as well as nonadrenaline. This results into heightened heart rate, sweating and increased blood pressure.

This physical response of the body is against Homeostatis, the state of physiological stability in humans. To return the body to this state, Allostatis occurs. Allostatis is the method the human body achieves stability once again. It is also how organisms cope with different states such as sleep and wakefulness.