Q. Someone sneaks up behind you and shouts, “Boo!” For a few seconds your heart beats faster. You did not run or do any physical activity that would increase your heart rate. What caused your heart to beat so fast?
So you know when you get scared or you’re speaking in public and you heart beats faster and you’re alerted by every single thing. Well, what causes that is a stress hormone called, epinephrine, commonly called adrenaline. Epinephrine is produced by adrenal gland, it has a fight-or-flight response, by pumping more blood through your blood or give your lungs more air. When you get scared, your brain sends a signal to the chromaffin cells to give off epinephrine. Then when these cells receive the signal, and give off epinephrine, it will give the person more energy. Although, epinephrine has some side effects like dizziness, lightheadedness, or blur your vision for a while.