We cannot just jump up in the middle of a class to use up our increased energy!

The major difference between stress now and stress thousands of years ago, is the way in which we deal with our physical stress response. In the caveman's days, the adrenaline, sugar, etc. was used up in a physical way. In today's life, we cannot always jump up in the middle of a math class and run around the block a few times to use up the increased energy. We have to stay seated. This means that all the physical changes that occurred in our bodies to prepare us for fight/flight, stay in our bodies and build up.

In small doses, these substances (listed at the Stress response diagram) actually can improve our health: they get the blood flowing a little faster, bringing oxygen and nutrients to our brain for mental energy, and help us in motivating us to work. But, chronic intense stress results in breakdown in our body's ability to re-establish a balance (homeostasis). For example, the cortisol hormone has a negative effect on the hippocampus in the brain and its increased release influences the immune system. Continual release of adrenaline and noradrenaline puts pressure on the heart muscle and thus people are placed at risk for heart disease.