Allostatic load
Encyclopedia
The term allostatic load, coined by McEwen and Stellar in 1993, is defined as the physiological consequences of chronic exposure to fluctuating or heightened neural or neuroendocrine response that results from repeated or chronic stress.
It is used to explain how frequent activation of the body's stress response, essential for managing acute threats, can in fact damage the body in the long run. Allostatic load is generally measured through a composite index of indicators of cumulative strain on several organs and tissues, but especially on the cardiovascular system.
Adaptation in the face of stressful situations and stimuli involves activation of neural, neuroendocrine and neuroendocrine-immune mechanisms. This adaptation has been called "allostasis
" or "maintaining stability through change", which is an essential component of maintaining homeostasis
. The main hormonal mediators of the stress response, cortisol
and epinephrine
(adrenaline), have both protective and damaging effects on the body.
In the short run, they are essential for adaptation, maintenance of homeostasis, and survival “allostasis
”. Yet, over longer time intervals, when called upon frequently, they exact a cost “allostatic load” that can accelerate disease processes. Allostatic load can be measured in physiological systems as chemical imbalances in autonomic nervous system
, central nervous system
, neuroendocrine, and immune system
activity as well as perturbations in the diurnal rhythms, and, in some cases, plasticity changes to brain structures.
Four conditions that lead to allostatic load are:
The effects of these forms of dysfunctional allostasis cause allostatic load and this, over time, leads to diseases. Allostatic load effects can be measured in the body. When tabulated in the form of allostatic load indices using sophisticated analytical methods, it gives an indication of cumulative lifetime effects of all types of stress on the body.
It is used to explain how frequent activation of the body's stress response, essential for managing acute threats, can in fact damage the body in the long run. Allostatic load is generally measured through a composite index of indicators of cumulative strain on several organs and tissues, but especially on the cardiovascular system.
Reactions
The hormones and other physiological agents that mediate the effects of stress on the body have protective and adaptive effects in the short run and yet can accelerate pathophysiology when they are over-produced or mismanaged this kind of stress can cause hypertension and is a lead to heart disease. This at times and even sometimes get you sick and make you have a very weak immue system.Adaptation in the face of stressful situations and stimuli involves activation of neural, neuroendocrine and neuroendocrine-immune mechanisms. This adaptation has been called "allostasis
Allostasis
Allostasis is the process of achieving stability, or homeostasis, through physiological or behavioral change. This can be carried out by means of alteration in HPA axis hormones, the autonomic nervous system, cytokines, or a number of other systems, and is generally adaptive in the short term...
" or "maintaining stability through change", which is an essential component of maintaining homeostasis
Homeostasis
Homeostasis is the property of a system that regulates its internal environment and tends to maintain a stable, constant condition of properties like temperature or pH...
. The main hormonal mediators of the stress response, cortisol
Cortisol
Cortisol is a steroid hormone, more specifically a glucocorticoid, produced by the adrenal gland. It is released in response to stress and a low level of blood glucocorticoids. Its primary functions are to increase blood sugar through gluconeogenesis; suppress the immune system; and aid in fat,...
and epinephrine
Epinephrine
Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...
(adrenaline), have both protective and damaging effects on the body.
In the short run, they are essential for adaptation, maintenance of homeostasis, and survival “allostasis
Allostasis
Allostasis is the process of achieving stability, or homeostasis, through physiological or behavioral change. This can be carried out by means of alteration in HPA axis hormones, the autonomic nervous system, cytokines, or a number of other systems, and is generally adaptive in the short term...
”. Yet, over longer time intervals, when called upon frequently, they exact a cost “allostatic load” that can accelerate disease processes. Allostatic load can be measured in physiological systems as chemical imbalances in autonomic nervous system
Autonomic nervous system
The autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils,...
, central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
, neuroendocrine, and immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
activity as well as perturbations in the diurnal rhythms, and, in some cases, plasticity changes to brain structures.
Four conditions that lead to allostatic load are:
- Repeated frequency of stress responses to multiple novel stressors;
- Failure to habituate to repeated stressors of the same kind;
- Failure to turn off each stress response in a timely manner due to delayed shut down; and
- Inadequate response that leads to compensatory hyperactivity of other mediators.
The effects of these forms of dysfunctional allostasis cause allostatic load and this, over time, leads to diseases. Allostatic load effects can be measured in the body. When tabulated in the form of allostatic load indices using sophisticated analytical methods, it gives an indication of cumulative lifetime effects of all types of stress on the body.
See also
- PsychoneuroimmunologyPsychoneuroimmunologyPsychoneuroimmunology is the study of the interaction between psychological processes and the nervous and immune systems of the human body...
- Hypothalamic–pituitary–adrenal axis
- Holmes and Rahe stress scale