The human body is endowed with the ability to protect from danger or to cope with stressful situations. Panic attack occurs when the protective system react when not needed. Going through a crisis. Your body is focusing on short-term surviving. The level of adrenaline and blood pressure increase, breathing becoming faster. The legs are ready to take the flight, the arms will be strained, as prepared for battle. Pupils are dilated, they get more light. You feel the danger lurking.