In the first stage of GAS called alarm reaction, the body releases adrenaline and a variety of other psychological mechanisms to combat the stress and to stay in control. This is called fight or flight response. The muscles tense, the heart beats faster, the breathing and perspiration increases, the eyes dilate, the stomach may clench. Believe it or not, this is done by nature to protect you in case something bad happens. Once the cause of the stress is removed, the body will go back to normal.