Stress is how we perceive, and then react, to our environment.
The stress reaction, or the fight-or-flight reaction, is a normal response to prepare us for survival. Under stress, the hypothalamus in the brain tells the pituitary gland to secrete the hormone ACTH. ACTH travels quickly to the adrenal glands, which are located above your kidneys.
The adrenal glands secrete the hormones cortisol and adrenaline. You are probably familiar with adrenaline—the hormone that causes a surge of dopamine and endorphins. These chemicals, along with adrenaline, cause the ‘adrenaline rush’, which is any activity that gets your heart pumping and your blood running faster through your veins.
For each person, this ‘rush’ could be caused by doing something risky, or something that creates extreme happiness. Adrenaline is also released in the body in time of major stress.
Cortisol is a steroid hormone released under stress; it helps to regulate blood sugar, and acts as an anti-inflammatory—as with the allergic response. Under prolonged stress, cortisol can break down muscles and cause you to hold onto, or even increase, body fat.
Cortisol can increase your blood pressure, cause miscarriages, dilute your urine, and increase liver detoxification. It can also increase your appetite, making you crave sugars and contributing to obesity. Another not-so-pleasant affect of cortisol is its effect on the immune system.
Cortisol is an immunosuppressant—it weakens your immunity, decreasing your ability to fight bacteria, viruses and cancer cells. The immune system is your internal armed services. When an invader, like a virus, enters the body, the body responds by sending out a type of white blood cell called a Natural Killer (NK) cell. Its role: seek and destroy cells infected by viruses and cancer cells.
Under prolonged stress, cortisol suppresses the function of the NK cell, thus allowing viruses to take hold and cancer cells to survive in the body. Individuals under constant stress have outbreaks of shingles and cold soars and, for some, the return of cancer or the diagnosis of cancer.
Cortisol is life-saving, but it can be a serious health hazard if not controlled.
Part 3 next
Ronald Glaser and Janice K. Kiecolt-Glaser, Stress-induced immune dysfunction: implications for health, Nature Reviews; Volume 5, March 2005; 243