Fight or Flight
Public speaking is your worst nightmare. You hear yourself introduced. It seems like an eternity from your chair to the front of the room. Your vision changes. Can others actually see your heart pounding? You break out into a cold sweat. You become dizzy, confused and can’t remember what you prepared to say. You face your peers. You see a sea of blank faces. You clear your throat. It’s so dry. All you want to do is run away from the podium but you know you must stand and deliver…
Have you heard of the “flight or fight response”? This is when your body prepares itself for a stressful event by either readying the body to quickly flee or to fight for your life. You see, back in the olden days, when our ancestors were about to be eaten by a saber-tooth tiger, there was no time to think about the situation, no time to analyze what to do. There was only time to act and act quickly.
The fight or flight response is a natural and efficient bodily reaction that is regulated by the sympathetic nervous system. It is actually a very helpful system to have when facing real danger. When we are exposed to an extreme stress, our heart rate rises which increases blood flow to the muscles, allowing us to run away or give us the strength to fight. Our breathing becomes rapid and shallow to increase our oxygen intake. All of our energy is directed to dealing with the stressor and unnecessary processes are shut down: digestion slows, the growth process is stunted, sexual function is impaired. (Food and sex are really not important when you are about to be eaten.) The higher functioning parts of our brain may also shut down because there is no need to think at a time like this. Glucose is released by the liver for energy.  
The stress response in the body works like this:
External stimuli cause our brains to judge a situation to be stressful. The stressor activates the hypothalamus in the brain, which sounds the alarm to the adrenal medulla and the pituitary gland. The adrenal medulla releases adrenaline which in turns controls the involuntary reaction of the body (heart rate, sweating, etc.). The pituitary gland secretes the hormone adrenocorticotropic (ACTH), which then tells the adrenal glands to release cortisol. This hormone is essential for releasing sustained amounts of glucose, reducing swelling and suppressing the immune system. 
Today we are no longer being eaten by saber-tooth tigers. (Well, we shouldn’t be, anyway.) However in our complex world we may be facing periods of prolonged, sustained stress. Our brains have become more sophisticated since ancient days, but that does not mean that we have lost the part of our brain that produces the fight or flight response. The same system that was in place to save us from a hostile environment is still functioning today, responding to stressors such as divorce, financial problems or other threats to our well-being.
Ideally, our bodies return to normal after our brains determine that the stress has passed, as the sympathetic nervous system is self-regulating. When it turns off, the parasympathetic nervous system, which regulates our bodies when they are at rest, turns on. However, if we are constantly perceiving extreme stressors, the sympathetic nervous system remains turned on. Sometimes the whole system just goes haywire when we are stressed for too long.
We need a certain amount of cortisol just to function every day. For example, we have heightened levels of cortisol in the morning so we can get out of bed and make that first cup of coffee. But prolonged, heightened levels of cortisol in the body can have negative side effects. Anxiety and depression, digestive issues, weight gain, heart disease, common illnesses and sleep disruptions are all side effects of elevated stress on the body. Prolonged exposure to stress may also impair our cognitive functioning, as higher cognitive functioning is not needed during the stress response.  
What can you do to relieve stress?
The mind and the body are connected so taking care of your body is as important as taking care of your mind. Because of problems with stress-related digestion, it is very important to eat a healthy, well-balanced diet. Exercise is really effective in reducing stress. When one exercises, the body releases endorphins, which can make you feel euphoric. Breathing exercises are very helpful in calming the body. Clearing your mind through some sort of meditation can also help to reset the stress response system back to normal. Don’t turn to vices to relieve stress such as excessive alcohol, tobacco, caffeine, or drugs. You are already stressed out - you don’t need to add more stress to your life by having to deal with the consequences of indulging in unhealthy habits, as well.
Try to identify what causes you stress and as much as possible eliminate it from your life. Of course this is not always realistic. If the stress cannot be entirely eliminated, maintaining a positive attitude and a healthy perspective on the situation is helpful in reducing stress. Things may not be as bad as you think. Besides, stress is always relative. You may be having to pay off a large debt, but there are people far worse off right now than you. Take the small stuff in stride. Of course, as always, a good sense of humor can deflate any stress. So what if you fell on top of someone on the subway and knocked them over? They will get over it. It’s actually pretty funny if you think about it. 
 [“What is the Stress Response?”by Saul McLeod. 2010 http://www.simplypsychology.org/stress-biology.html ]
 [“What is the Stress Response?” Pamela Young http://www.cfids.org/cfidslink/2006/stress1.pdf ]
 [“Biological Basis of Stress Response” http://www.erin.utoronto.ca/~w3psy398/g5/stress.pdf]
 [“Chronic Stress Puts Your Health at Risk: Chronic stress can wreak havoc on your mind and body. Take steps to control your stress.” http://www.mayoclinic.com/health/stress/SR00001]
 [ “The Biology of Being Frazzled”, Amy F.T. Arnsten. 1998 http://www.colorado.edu/intphys/Class/IPHY3700_Greene/pdfs/MindBodyHealthArticles/frazzled.pdf]
 [“Tips to manage Anxiety and Stress”http://www.adaa.org/living-with-anxiety/managing-anxiety/tips]