Answer:
Adrenaline
Step-by-step explanation:
Adrenaline is a chemical released when you are in stress or, to coin it better, in "panic mode". It helps boost your stamina, and gears you towards flight in the fight v. flight response. However, when needed, you have that extra boost of stamina in case you do need to fight. Your blood pressure will rise, and your heart will beat faster, as well as you feeling your muscles tense up and body heating up.