Stressor
A stressor is anything in the outside world that knocks you out of homeostatic balance. But when we consider that stress experienced by humans is generally psychological or social, we have to expand on the notion of stressors merely being things that knock you out of homeostatic balance. A stressor can also be the anticipation of that happening.
References
- Sapolsky, Robert. (2004). Why Zebras Don’t Get Ulcers Chapter 1. Why Don’t Zebras Get Ulcers? (p. 16). New York, NY: Henry Holt and Company.