| Stage | Name | Description | |-------|------|-------------| | 1 | | The body detects a stressor; sympathetic nervous system activates “fight-or-flight.” Adrenaline and cortisol rise. Short-term resistance drops. | | 2 | Resistance | If stress continues, the body adapts. Cortisol levels remain elevated but stable. Resources are mobilized to resist the stressor. | | 3 | Exhaustion | Prolonged stress depletes adaptive energy. Resistance collapses, leading to fatigue, burnout, illness (e.g., ulcers, hypertension), or death. |

The PDF provides a thorough and well-structured overview of Selye's life and work. The author's writing style is clear, and the document is well-organized, making it easy to follow. However, some readers may find the content to be somewhat dense and technical, particularly those without a background in biology or medicine.

Selye's most notable work is the development of the General Adaptation Syndrome (GAS) theory, which describes the body's response to stress. According to Selye, GAS is a three-stage process:

The PDF on Hans Selye provides several key takeaways: