What is Stress?
Though stress can come from outside sources (a demanding boss, a hurricane, freeway traffic, etc.) or internal sources (worry, perfectionism, disease, etc.), it affects our bodies physically and emotionally. When we experience stress, our bodies respond whether we want them to or not. This stress response is nature's way of keeping us alive. Called the fight or flight syndrome, it prepared our bodies to respond to danger. Either we tackled the source of the stress, usually a wild animal or an invading human, and fought it, or we ran away. If we prevailed over the wild beast or we ran away, we lived another day and our species survived. This fight or flight syndrome is also what is responsible for heroic and almost superhuman efforts in times of crisis, such as when someone lifts the front of an automobile off of an injured person after an accident.
The Brains ReactionThe first thing that happens when we are under stress is a part of our brain, the hypothalamic-pituitary-adrenal (HPA) system is activated. This recognizes the stress as danger and pumps out neurotransmitters such as dopamine, norepinephrine, and epinephrine (also known as adrenaline). These neurotransmitters stimulate the part of the brain called the amygdala that registers an emotional response, usually fear, but can be other emotions like anger. Then the hippocampus, another part of the brain, stores this emotion in long-term memory. That means that every time we see the stressor (the wild beast), we will react with the emotion that is stored there (fear) and whatever memories we have of how we reacted physically to the stress (fight or flight). These neurotransmitters also interfere with areas in the front of the brain that deal with concentration, inhibition, rational thought, and short-term memory. This makes us react on a more primitive level; we fight or run. We can't deal with complex intellectual responses to the stress; we just react.
The Physical ReactionOnce the brain gets activated, other parts of the body come into play. We start to breathe rapidly and our hears beat faster. This brings blood and oxygen to our bodies, especially our limbs, so that we can get ready to fight the beast or run away. Our spleens also pump out more red and white blood cells, allowing our bloodstream to carry more oxygen. Cortisol, a corticosteroid hormone, is produced by the adrenal glands. It shuts down sections or our immune system and send white blood cells and immune molecules to places where we might be injured, such as our skin, lymph nodes, and bone marrow. Cortisol also raises our blood pressure and blood sugar levels.
We get a dry mouth as body fluids are drawn away from non-essential areas like the mouth. We may also have trouble swallowing as our throat muscles spasm.
Though white blood cells rush to our skin, red cells are marshaled to the heart and muscles. This is nature's way of protecting us from blood loss in case we get gored by the wild beast. However, we experience cold, clammy hands and our hair may even seem to stand up as the skin on our scalps tighten.
Finally, all non-essential body systems are shut down so that we can react to the stress. This means that digestion is stopped or severely slowed.
Normally, our bodies return to normal function once the danger is gone. This is known as the relaxation response. Since most of us won't encounter a wild beast or traumatic every day, this is usually a short-lived experience. However, we can experience a stress reaction from a variety of other sources, any of which may not be as surprising or intense as meeting a wild beast, but which can last for longer periods.