Stress is a physiological and psychological adaptation to physical, mental, or emotional stimuli that negatively affects the body. From an evolutionary perspective, stress queued our bodies into providing extra energy and adrenaline required for moments of survival. The events were usually abrupt and short term, such as escaping a predator or enemy, or stalking prey for food. Today, most stress occurs as a result of the modern "first world" lifestyle rather than physical threats related to our immediate survival.
During Stress
When you are under stress, your body goes through a number of stages collectively known as the general adaptation syndrome. Under the initial short-term "alarm reaction" or "fight-or-flight" response, your body secretes adrenaline and other hormones from the adrenal glands, located on top of your kidneys. This results in a number of reactions that increase heart and breathing rates and raise blood pressure. The combination of factors promotes increased blood flow, oxygen, and glucose availability to your brain, heart, lungs and muscles in preparation for a response. The adrenal hormones also increase blood sugar levels as your liver releases stored glucose into the bloodstream. Fatty acids are also mobilized into the bloodstream, providing additional nutritional support if needed. Digestion slows or stops, cholesterol levels rise, and the blood becomes more prone to clotting. Sweat production also increases to reduce body temperature and help eliminate toxins. The combination of actions are the result of our natural response mechanism to sudden change and this series of initiations and reactions has ensured our survival as a species.
The initial alarm reaction is followed by an adaptation or "resistance" stage that allows your body to continue dealing with a stressor long after the alarm reaction has subsided. The pituitary gland increases adrenocorticotropic hormone (ACTH) production, stimulating the adrenal cortex to release cortisone and cortisol hormones that break down fat and convert protein to energy. These hormones also promote sodium retention, maintaining elevated blood pressure. High levels of cortisol can weaken the immune system, interfere with white blood cell function, disrupt brain and nervous system function, and cause a number of other physical problems, outlined under What to Expect, below.
"Exhaustion" follows the resistance stage and may result in a complete collapse of body systems or one or more organs or functions. This results primarily from either potassium ion loss and/or adrenal glucocorticoid hormone depletion. Potassium loss leads to poor cell function and eventual death. Adrenal glucocorticoid hormone depletion results in hypoglycemia where cells cannot obtain enough glucose and other nutrients to ensure proper function. Exhaustion may also be caused by weakened organs as long-term stress significantly strains the adrenals, blood vessels, heart, and immune system.
