I always talk to my students about stressing out during an exam. Your body doesn’t know the difference between an exam and a life or death situation; if your body stresses out you go into the stress response. This starts with the release of adrenaline and noradrenaline which both act as a neurotransmitter and as a hormone. They trigger the rest of your body to go into a fight or flight response. This means reduced digestion, increased heart rate, increased blood pressure, and a number of other responses. The whole point is to give you the best physical ability to escape a physical threat. This is a serious disadvantage during an exam because you need brain ability not physical ability. So, the goal is to not stress out.
In terms of general health this also has an impact. For individuals with cardiac issues they often have to take beta blockers. Beta blockers block the receptors for the adrenaline and noradrenaline. This means that when you start to stress and your body releases the chemicals the receptors for those chemicals are already occupied by the beta blockers. If the chemicals can’t get to the receptors they can’t trigger the stress response. This results in keeping a low blood pressure and lower heart rate which reduces the chances of a heart attack for individuals who are at higher risk.
So the biggest challenge with the stress response is that very few of us experience stress that requires a physical response, most of us experience emotional or mental stress. As a result the stress response that has evolved to allow us to survive in physically demanding environments has negative impacts today.