Allostasis refers to the ability of an organism to maintain stability or balance through adaptive changes in physiological processes rather than through the maintenance of fixed set points. It is a more recent concept in physiology and neuroscience that expands on the traditional view of homeostasis. The term "Allostasis" was first used in the 1990s to describe the physiological changes that occur in response to stress and other environmental challenges.
Allostasis involves the activation of physiological systems, such as the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system, in response to stressors. These systems activate a cascade of physiological changes that prepare the body for the "fight or flight" response, such as the release of stress hormones like cortisol and adrenaline, which increase heart rate and blood pressure, and decrease the activity of non-essential functions like digestion.
However, chronic or prolonged exposure to stress can lead to allostatic load, which is the cumulative wear and tear on the body caused by repeated activation of physiological systems. This can lead to negative health outcomes such as increased risk of cardiovascular disease, diabetes, and mental health disorders.
At a neural level, allostasis is also associated with changes in the activity and structure of neural circuits that mediate the stress response. For example, chronic stress can lead to changes in the activity of the hippocampus, a brain region involved in memory and emotional regulation, resulting in altered stress response and cognitive decline.
Overall, allostasis is a dynamic process that allows organisms to adapt to environmental challenges, but chronic exposure to stress and allostatic load can have negative consequences.