Stress and Survival
Stress is defined as any disruption of homeostasis or balance. It is a force that produces strain on the body or mental strain or suspense. Many of us face stress on a regular basis. It is difficult to maintain a stress-free life given the numerous demands and challenges that confront us each day. We are routinely bombarded with psychological and physical stressors that we have come to accept as a normal part of life. It is commonplace to brag about how stressed we are as if it were a badge of honor. Multitasking, long work hours, sleep deprivation, poor nutrition, family duties and social obligations slowly take their toll on us mentally and physically. We are left feeling exhausted and worn out. We battle stress but eventually it overcomes us.
Everyone reacts differently to stress depending on his or her genetic make-up, family upbringing, and social circumstances. However, certain events are more likely to trigger extreme stress responses. These events include the death of a spouse or family member, marriage, birth of a child, divorce or separation, injury or illness, being fired from a job, retirement, imprisonment, financial problems, home foreclosure, and any major life-altering events. One common thread that these events have in common is that they are either uncontrollable or unpredictable and often leaves one feeling helpless and vulnerable. Stress may also be caused by physical factors such as chronic infections, inflammation and pain, food intolerance, heavy metal and environmental toxins, temperature extremes, sleep deprivation, excessive exercise, nutritional imbalances, prescription medications, surgery, and body trauma.
Stress has existed since the beginning of time. Its effects are far reaching for all living organisms. Over time, the need to adapt to stress led to the development of a sophisticated survival mechanism. The effectiveness of this survival mechanism determines who lives and who dies; thereby, weeding out the unfit and allowing the strong to survive. To illustrate this stress survival mechanism, let us examine the following scenario.
While viewing the Discovery Channel the following scenario unfolds. A gazelle grazes peacefully, unaware of any lurking danger. A hidden predator fixes its gaze on the chosen prey. It inches forward in the grass, tensed, coiled and ready to attack. Suddenly the attack begins. The gazelle catches a glimmer of movement out of the corner of its eye, and alarm bells go off in its head. It springs into action, a perfect running and bounding machine. There is no hesitation because to hesitate could mean certain death. The gazelle possesses an innate unconscious survival mechanism that springs into action in response to a threat. We watch in fascination as the gazelle tries to outrun and outmaneuver its predator until it escapes or is caught.
The whole sequence is never more than a few seconds or minutes at the most. The innate phenomenon witnessed in the gazelles headlong run is known as the stress response or fight-or-flight reaction. This response allows the gazelle to instinctively shift into high gear to escape an immediate threat. The gazelle becomes faster, more aware of its surroundings, physically powerful, and quick to react.
Much of the stress response is coordinated by the hypothalamus (see figure 1), located in the brain that triggers a series of messages utilizing hormones and the nervous system. The hypothalamus produces corticotropin-releasing hormone (CRH), which then stimulates the pituitary gland, also located in the brain, to release adrenocorticotropic hormone
(ACTH). Under the influence of ACTH, cortisol, a steroid hormone, is secreted. Cortisol is produced by the adrenal gland, which is located just above the kidneys.
Figure 2 depicts the effects of stress on the hypothalamus, which stimulates the pituitary and adrenal gland to produce ACTH and cortisol, respectively. Cortisol in turn controls the release of ACTH and CRH, which consequently inhibits its own production.
Cortisol is necessary to deliver energy (glucose) to active muscles and the brain during times of stress. Energy is diverted from the digestive tract and kidneys to be used by the muscles to run or fight and repair bodily injuries. The immune and reproductive systems are temporarily altered or shut down. Growth processes in the body are also slowed. Anything that is not immediately useful in the stress response is put on hold until the threat has passed. Adrenaline (epinephrine) and noradrenaline (norepinephrine), which are also released from the adrenal gland, increase energy, muscle strength, heart rate and blood pressure. When the stress response is triggered, the gazelles nervous system goes into overdrive, creating a highly powered machine that can efficiently deal with a predators attack. Eventually, the stress of the pursuit subsides when the gazelle either escapes or is eaten by the predator. In either case, escape or death, the stress response normally subsides.
Humans also possess this innate stress response. In times past, historians portrayed mankind as predators. However, recent evidence reveals that we too were prey for thousands of years. Mounting fossil evidence has forced scientists to revise the earlier Man the Hunter theory of humans as super predators. The sad fact is that the prehistoric skulls and bones of our ancestors show clear perforations that match the teeth and claws of predators such as eagles, hyenas, cheetahs, crocodiles and other hunting carnivores. It appears that much of our survival adaptation was driven by the stress of escaping predators. Therefore, the stress response has played a crucial role in the survival of our species.
In present times, humankind has created a modern environment that is in many ways safer and more accommodating than the world of our ancestors, yet filled with stressors that our ancestors did not face. Today, unfortunately, the stress response that enabled us to survive in past times is now making us sick, and is the underlying cause of many major illnesses. Chronic stress has been linked to the six leading causes of death in the western world, which include heart disease, lung disease, cancer, car accidents, liver disease, and suicide. It is also associated with a wide range of symptoms and diseases. The stress response over time becomes problematic because of the heavy toll it takes on the body. The discrepancy in the benefits of the stress response lies in the heavy cost of this defense mechanism over a long period of time. It is important to evaluated for the effects of stress when you visit your doctor. Our practice specializes in laboratory and screening this to identify chronic stressors, which are affecting your health. For more information about the impact of stress on your health, be sure to read The Stress Connection by Drs. Eldred Taylor and Ava Bell-Taylor.
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