Understanding the Physiology of the stress response - the basics
Defining the regulatory system in place to mount and stop a stress response:
"Adaptation in the face of potentially stressful challenges involves activation of neural, neuroendocrine and neuroendocrine-immune mechanisms. This has been called “allostasis” or “stability through change” by Sterling and Eyer (Fisher, S. Reason, J. (eds): Handbook of Life Stress, Cognition and Health. J. Wiley Ltd. 1988, p. 631), and allostasis is an essential component of maintaining homeostasis [the body regulatory system to maintain survival]. When these adaptive systems are turned on and turned off again efficiently and not too frequently, the body is able to cope effectively with challenges that it might not otherwise survive. However, there are a number of circumstances in which allostatic systems may either be overstimulated or not perform normally, and this condition has been termed “allostatic load” or the price of adaptation (McEwen and Stellar, Arch. Int. Med. 1993; 153:2093.)"
McEwen, BS. (1998). Stress, Adaptation, and Disease: Allostasis and Allostatic Load. Annals of the New York Academy of Sciences. 840, pp. 33–44.
Why was it necessary to name the system in place, when the body can no longer cope: "the wear and tear" on the body, which accumulates as an individual is exposed to repeated or chronic stress?
"Stress is frequently seen as a significant contributor to disease, and clinical evidence is mounting for specific effects of stress on immune and cardiovascular systems. Yet, until recently, aspects of stress that precipitate disease have been obscure. The concept of homeostasis has failed to help us understand the hidden toll of chronic stress on the body. Rather than maintaining constancy, the physiologic systems within the body fluctuate to meet demands from external forces, a state termed allostasis. In this article, we extend the concept of allostasis over the dimension of time and we define allostatic load as the cost of chronic exposure to fluctuating or heightened neural or neuroendocrine response resulting from repeated or chronic environmental challenge that an individual reacts to as being particularly stressful."
McEwen, BS. Stellar, E. (1993). Stress and the individual. Mechanisms leading to disease. Archives of internal medicine. 153 (18), pp. 2093–2101.
Why does it mean for you?
"Experience tells us that the social and physical environments in which people live and work have a huge effect upon psychological states.
"Experiences involving social interactions and events in the physical environment are processed by the brain and are usually referred to under the rubric of “stress”. We now know, from animal models, that the brain changes in structure and function with experiences, including those of chronic stress, and that these changes in brain represent “adaptive plasticity”, in that they are largely reversible and appropriate for the conditions that cause them.
"Indeed, the brain is the key organ of the adaptive and maladaptive responses to stress because it determines what is threatening and, therefore, potentially stressful, as well as initiating the behavioural, as well as many of the physiological responses to the stressors, which can be either adaptive or damaging (McEwen, 1998; McEwen, 2007). Stress involves two-way communication between the brain and the cardiovascular, immune and other systems via the autonomic nervous system and via endocrine mechanisms.
"Beyond the “flight or fight” response to acute stress, there are events in daily life, including the individual life style, that produce a type of chronic stress and lead over time to wear and tear on the body (“allostatic overload”). Yet, the hormones and other mediators associated with stress and adaptation protect the body in the short-run and promote adaptation (“allostasis”).
"Early life events influence lifelong patterns of emotionality and stress responsiveness and alter the rate of brain and body ageing. The amygdala and prefrontal cortex, as well as the hippocampus, undergo stress-induced structural remodelling, which alters behavioural and physiological responses, including anxiety, aggression, mental flexibility, memory and other cognitive processes."
McEwen, BS. (2009). The Brain is the Central Organ of Stress and Adaptation. Neuroimage. 47 (3), pp. 911–913.
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The main symptom of Chronic Stress is Fatigue (read more), because stress affect blood sugar levels due to the main stress hormone Cortisol, which can lead to Hypercortisolemia, which can be exacerbated by poor diet and lifestyle choices:
"Long-term, or Chronic Stress, suppresses or dysregulates immune responses. Because the body does not quite switches back on – and sleep depravation keeps it so –, it is not able to do the tasks it does best: healing and repair.
Without healing and repair, inflammatory immune cells are activated, inducing low-grade chronic inflammation (generating very little symptoms, at the beginning). This subsequently also “suppressed the numbers and function of Immunoprotective cells,
"Chronic stress hammers away at the cardiovascular system, basically making it work harder and harder.
With the increase in blood pressure that accompanies repeated stress, damage occurs at branch points of the arteries.
Adrenaline triggers changes to enhance blood clotting.
These changes contribute to the development of atherosclerosis.
When the adrenal glands are fatigued they continue to function, but hormones can:
The Circadian rhythm of Cortisol is regulated by the sleep-wake cycle.
Secretions are characterised by a steep increase in the morning, followed by a gradual tailoring off until about midnight (circulating levels are at their lowest).
The adrenal hormones are integrally involved in how energy is produced and where it is allocated.
When blood glucose levels drop, the adrenals release Cortisol which triggers the liver to produce more glucose.
Cortisol increases the amount of glucose available to the brain and muscles and limits energy supplied to digestion, growth and reproduction (nonessential, or even detrimental in a survival situation).
Stress also categorically alters digestive functions. The body cannot afford to waste energy digesting or producing enzymes to digest food and detoxify toxins. Motility is also reduced; gastric juices production is annulled and gastric emptying is slowed down, which can lead to putrefaction of undigested food, thus having a direct impact on the composition of the gut flora, which is also altered by the stress response itself."
Read the complete article
Sleep is often disturbed and can become quite problematic, when an individual finds hard to fall asleep and/or stay asleep, to feel refreshed in the morning, and keep sugar and Cortisol levels under check.
Recent studies "suggest that sleep disruption may be most detrimental to bone metabolism earlier in life, when bone growth and accrual are crucial for long-term skeletal health," demonstrating that lack of sleep has direct effect on bone mass, and osteoporosis, and it is more detrimental in younger chronically stressed individuals.
A must-read article:
The Endocrine Society. "Prolonged sleep disturbance can lead to lower bone formation." ScienceDaily. ScienceDaily, 2 April 2017. www.sciencedaily.com/releases/2017/04/170402111317.htm.
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