We will consider a little background information to give some rigour to the term we have been using—stress. Living organisms have regular patterns and routines that involve obtaining food breeding, migrating, molting, and hibernating. The acquisition, utilization, and storage of energy reserves (and other resources) are critical to lifetime reproductive success. There are also responses to predictable changes, e.g., seasonal, and unpredictable challenges like storms and natural disasters.
Social organization in many populations provides advantages through cooperation in providing basic necessities and beneficial social support. But there are disadvantages owing to conflict in social hierarchies and competition for resources. Here, we discuss the concept of allostasis (maintaining stability through change), as a fundamental process through which organisms actively adjust to both predictable and unpredictable events. One of the central concepts in biology is the notion of a ‘balance’ where all systems in the body are maintained at a certain optimum level.
The scientific term is homeostasis’ and it is defined as the stability of physiological systems that maintain life. Typically, it applies to a limited number of systems such as acidity, body temperature, glucose levels, and oxygen tension that are truly essential for life and are, therefore, maintained within an optimal range.
This concept has been expanded in recent years to consider a number of changes that take place in our body in response to different events. The scientific term used is ‘allostasis’ which can be defined simply as achieving stability through change. This is a process that supports homeostasis, i.e., those physiological parameters essential for life as environment change or the person grows through different stages in life (for example, a stage change occurs after childbirth).
This means that the ‘set points’ and other boundaries of control must also change. The body has a number of tools to achieve allostasis which also helps us to clarify an inherent ambiguity in the term ‘homeostasis’ and distinguishes be-tween the systems that are essential for life (homeostasis) and those that maintain these systems in balance (allostasis) as the environment and life stages change. A number of changes occur in the body to retain allostasis and the primary actors (mediators) in this process are the hormones released by the hypothalamus and the pituitary gland (more of this in the following sections).
The allostatic state refers to altered and sustained activity levels of the primary actors that integrate physiology and associated behaviours in response to changing environments and challenges such as social interactions, weather, disease, predators and pollution. An allostatic state results in an imbalance of the primary mediators, reflecting excessive production of some and inadequate production of others. Examples are hypertension, a perturbed rhythm during a period of major depression or after chronic sleep deprivation, chronic elevation of inflammatory cytokines, low Cortisol in chronic fatigue syndrome, and imbalance of corticotropin releasing factor (CRF), and cytokines that increase risk for autoimmune and inflammatory disorders.