Fight or Flight Response
Walter B. Cannon, a physiologist, laid the groundwork for the modern meaning of “stress” at Harvard around the turn of the century. He was the first to describe the “fight or flight response” as a series of biochemical changes that prepare you to deal with threat or danger. Primitive man needed quick bursts of energy to fight or flight response served you well, such as when you had to weave through an aggressive defense to make a touchdown. These days, however, when social custom prevents you from fighting or running away, this “emergency response” is rarely useful.
Fight or Flight Response
Hans Selye, the first major researcher on stress, was able to trace exactly what happens in your body during the flight response. He found that any problem, imagined or real, can cause cerebral cortex (the thinking part of the brain) to send an alarm to the hypothalamus (the main switch for the stress response, located in the midbrain). The hypothalamus then stimulates the sympathetic nervous system to make a series of changes in your body. Your heart rate, breathing rate, muscle tension, metabolism, and your extremities and digestive system into the larger muscles that can help you fight or run. You experience butterflies in your stomach. Your diaphragm and your anus lock. Your pupils dilate to sharpen your vision and your hearing becomes more acute.
Unfortunately, when the fight or flight response continues unchecked during times of chronic stress, something else happens that can have long-term negative effects. Your adrenal glands start to secret corticoids (adrenaline or epinephrine, and norepinephrine), which inhibit digestion reproduction, growth, tissue repair, and the responses of your immune and inflammatory systems. In other words, some very important functions that keep your body healthy begin to shut down.
Fortunately, the same mechanism that turns the stress response on can turn it off. This is called the relaxation response. As soon as you decide that a situation is no longer dangerous, your brain stops sending emergency signals to your brain system, which in turn ceases to send panic messages to your nervous system. Three minutes after you shut off the danger signals, the fight or flight response burns out. Your metabolism, heart rate, breathing rate, muscle tension, and blood pressure all return to their normal levels. Herbert Benson (1975) suggests that you can use your mind to change your physiology for the better, improving your health and perhaps reducing your need for meditation. He coined the term “the relaxation response” to refer to this natural restorative process.
