Source : helpguide.org
Stress is your body’s way of responding to any kind of demand or threat. When you feel threatened, your nervous system responds by releasing a flood of stress hormones, including adrenaline and cortisol, which rouse the body for emergency action. Your heart pounds faster, muscles tighten, blood pressure rises, breath quickens, and your senses become sharper. These physical changes increase your strength and stamina, speed your reaction time, and enhance your focus. This is known as the “fight or flight” or mobilization stress response and is your body’s way of protecting you.
More :What is stress?