Adrenaline is a molecule that is made up of carbon, hydrogen, oxygen, and nitrogen atoms. Adrenaline is like a fight or flight response in your body when it faces a threat. When encountering a treat around you, signals of the adrenal glands release adrenaline molecules into your body. This increases the bloodstream making your heart rate and blood pressure go faster. It expands the air passages of the lungs, it makes the pupils bigger to take in more light, and it makes muscles tense up. Adrenaline also increases your blood levels to give you a bunch of energy to fight it or run from it. All of this happens so fast that your body does this without even thinking about it.