The Physiology of Stress

Can Stress Make You Sick?

What happens in our body during stress, and how do we respond to these reactions?

Our lives bring us different things every day and, as a result, we respond to them emotionally and physiologically. At some point, everybody feels stressed. Stress is a normal physiological and psychological reaction to a threat. It was favored by natural selection throughout our evolution because it’s the only purpose in promoting our survival. Thus, whether it is a physical threat (a car crash ) or psychological ( a deadline or an argument with someone), the response to stress kicks in to help us deal with the situation.

The chain of reactions

Stress response involves a complex interaction of many-body systems, mainly to make the bodywork more effectively and to minimize all unnecessary functions. It is as if the body switches on a survival mode, where all the energy and functions are directed to fighting a threat.

It is achieved via the autonomic nervous system (ANS) , which creates a nonconscious automatic response, preparing to fight and survive. The response is controlled by the hypothalamus region in the brain, which initiates the release of corticosteroid hormones from adrenal glands into the bloodstream (epinephrine, norepinephrine, and cortisol). The chain is followed by:

  • increased activity in the central nervous system (CNS) and, therefore, mental activity
  • increase in heart rate – an increase of cardiac output with increased blood pressure
  • dilation of airways and increased inhalation (delivering O2 to the brain and muscle via blood circulation)
  • the reactions above promote faster metabolism and blood flow to limbs and muscles (increasing contraction ability). The response is supported by the release of glucose and fatty acids.
  • dilation of pupils ( allowing light, to sharpen eyesight)
  • regulation of body temperature and composition via sweat glands
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In other words – you are ready to run or fight.

Although, as it has been mentioned earlier, the work of other body systems temporarily minimized, which includes:

  • reproduction system
  • immune system
  • digestive system
  • decreased functioning of the intestinal tract and kidneys

As a result, we achieve a state effective for survival – speed, alertness, strength, emotional sharpness. This response happens automatically in seconds. Usually, when the stressor disappears, the reaction is soon brought down by the parasympathetic nervous system (PNS), which returns things to normal. When the stressor persists for a longer time or reappears consistently, the human body enters a state of chronic stress. As effectively as the body responds to stress, it’s regulated performance during prolonged stressful conditions starts overloading and failing, eventually leading to different health problems.

Don’t get me wrong – speeding is fun, but what happens to your car if you “push” it for hours?

Different responses to stress

An article on “Understanding of stress” includes an unusual psychological description of our responses. According to psychologist Connie Lillas,”there is a driving analogy to describe the three most common ways people respond to stress :

  • foot on the gas – an angry agitated stress response
  • foot on the brake – a withdrawn or depressed stress response
  • foot on both – a tense and frozen stress response”

The response to stress depends on a variety of factors, such as a person’s sex, age, mental state (emotional control and attitude), and physiological state. Therefore, what is stressful to one person might not be stressful for another.

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Chronic stress

According to Dr. Harbuz (Bristol University): “a single exposure to a particular stressor can reduce the response to that same stimulus several weeks later.” It suggests that our body can adapt to certain stressors through repeated exposures, on the condition that regulatory systems work well, although, it is not always the case.

When our systems do not cope, a long term exposure to stress leads to major changes of neurotransmitters in the brain, excess of corticosteroids in the blood, and other neuroendocrine changes. These changes are associated with the occurrence of depression, rheumatoid arthritis, risk of heart strokes, sleep problems, skin conditions, etc. Thus, when the balanced state (homeostasis) is not achieved you are fighting not only against stress but against yourself.

As I said before, everybody gets stressed at some point. And though, due to evolution, we are prepared to fight, sometimes we have to know how to take control and manage stress for our own well being. Driving a car when you know how is safer.

References :

  • Briefing by Dr. Harbuz : Stress Hormones and your brain, 1999, Published By British Society of Neuroendocrinology
  • Understanding Stress, “Signs and symptoms of stress overload” chapter, by
  • Other Articles :
  • The Stress Response: Men vs. Women

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