Physiology of Stress Response

Whether a bear suddenly jumps at you from the woods on a hiking trail, or your plane suddenly drops in altitude during flight, your body reacts similarly. First, your brain receives the information about the threat or hazard you are facing, mobilizes the stress response mechanism which immediately sends an emergency signal alerting the hypothalamus, the control center of your brain about the situation. The hypothalamus signals the pituitary gland, the master gland, to release adrenocortical hormone (ACTH) which triggers the release of more cortisol, a stress hormone, and adrenaline into the bloodstream. Cortisol elevates your blood sugar and mobilizes energy for quick response and escape, while adrenaline provides more energy to fight for survival.These chemicals elevate the body’s metabolism, heart rate, breathing rate, and blood pressure. Blood vessels open wider allowing more flow of blood to large muscles, alerting them for action if necessary. Throughout the duration of the stress response, the amount of blood pumped by the heart quadruples providing more energy to combat the situation. Instead of going to the skin, kidneys, or guts, blood is diverted to the muscles providing more energy to fight or flee. The airways dilate, breathing rates, blood pressure, and heart rate increases. The liver quickly starts to convert glycogen, your body’s raw material for energy into glucose or blood sugar to supply extra energy and power for for battle or retreat. More glucose is released by the liver to increase the body's energy supply if the need be. These physical and metabolic changes prepare you with the energy to react quickly and handle the danger or emergency effectively. Although the stress response puts enormous burdens on the nerves, the nervous system is very elastic and returns quickly to its original and normal state, ready to respond again and again to other stresses when needed. In the present age, the modern man and woman do not confront hungry and angry animals like our ancient ancestors: however, the stress response remains the same. For example, your stress response is always triggered when a car suddenly swerves into your own driving lane or when your shoe suddenly slides on a slippery snowy road. Although we no longer live under the threat of wild animals in the forest, our long work hours, long commutes, frustrating traffic jams, bad relationships and marriages, tough economy, mean bosses at work, errant kids, abusive spouses, negative newscasts from the media, abnormal and aggressive pursuit of material things, contributes highly to a life full of stress.