Stress Photo:

Stress

Photo: http://www.lam.mus.ca.us/cats/encyclo/smilodon/

Stress: The Importance of Allostasis

The term came into being in the 1980’s as a newer more appreciative way to view the body’s rapid and efficient methods of dealing with stress.

Allostasis refers to the body’s ability to maintain stability amidst change.

M Lu, N Halfon

Allostasis: Maintain Stability through Change

McEwen BS. Protective and damaging effects of stress mediators. N Eng J Med. 1998;338:171-9.

Allostasis: Wear and Tear

There are, however, situations that ignite stress response in which neither fight nor flight is an option….the response cannot help us toward resolution. Then, deprived of its natural result, the system designed to protect us begins to cause wear and tear illness and vulnerability.

ALLOSTASIS TO ALLOSTATIC LOADFour Scenarios

McEwen B. New England J. Med. 1998

Stress and Biology: Allostatic loading

Unremitting chronic stress, or severe trauma, particularly at windows of vulnerability and opportunity in human development.

Inability to adjust. Not hearing the “all-clear” signal Feedback loops impaired.Practical leadership action: 1. Foster conditions to prevent stress

and severe trauma. 2. Strengthen capacity to deal with stress. 3. Promote healing from stress and trauma.

What we often mean by “stress” is being “stressed out”!

Feeling overwhelmed, out of control, exhausted, anxious, frustrated, angry

What happens to us?

Sleep deprivation

Eating too much of wrong things, alcohol excess, smoking, etc.

Neglecting regular, moderate exercise

All of these contribute to allostatic load Psychosocial stress is a major factor

Levels of stressful experiences:Their causes, consequences and why we experience them!

HPA Axis Hypothalamic-pituitary-adrenal axis

Initiated in the hypothalamus gland, it is the cornerstone of allostasis. Impaired HPA axis function from toxic stress leads to chronic high levels of cortisol. Prolonged high levels of cortisol suppress immune function, increase inflammation, and may lead to LBW,preterm birth, diabetes, c-v disease, etc. Toxic stress may thus result in a hyper-reactive, dysregulated HPA axis.

Two possible mechanisms: Cumulative “wear and tear” (weathering) throughout the life cycle and fetal or childhood programming.

Social environment and healthCentral Role of the Brain

McEwen B. New England J. Med. 1998

Behavioral responses (“lifestyle”) as well as stressful experiences

MacArthur Foundation Research Network on Socioeconomic Status and Health

Prenatal Programming of the Hypothalamic-Pituitary-Adrenal Axis

Welberg LAM, Seckl JR. Prenatal stress, glucocorticoids and the programming of the brain.J Neuroendocrinol 2001;13:113-28.

CRHAVP

ACTH

Cortisol

STRESS

Acute - enhances immune,Memory, energy replenishment,Cardiovascular function

Chronic - suppresses immune,Memory, promotes boneMineral loss, muscle wasting;Metabolic syndrome

Many targets for cortisol

Stress, allostasis and allostatic load

Mediators of stress and adaptationNETWORK OF ALLOSTASIS

CNS function

Cardiovascularfunction

Metabolism

Immune function

Dysregulation by Biphasic and non-linear

-unhealthy lifestyle, poor sleep, toxic chemicals -feed into network of allostasis (eg elevated inflammation, cortisol)

Positive Stress vs. Toxic Stress Positive Stress

Increased cardiac output

Increased available glucose

Enhanced immune functions

Growth of neurons in hippocampus & prefrontal cortex

Toxic Stress

Hypertension & cardiovascular diseases

Glucose intolerance & insulin resistance

Infection & inflammation

Atrophy & death of neurons in hippocampus & prefrontal cortex