Homeostasis
Last updated: November 6, 2025
Homeostatic mechanisms that maintain a complex biopsychosocial balance are central to my theory of rehabilitation. When I first considered homeostasis in this context, I did not realise how long ago these ideas had been proposed. My published paper includes some references and evidence. This paper discusses the issues in more detail, including a historical perspective. Understanding homeostasis and its key role in a person’s life will help when offering rehabilitation to support their natural adaptation. The process concerns the goals someone has, which are covered on the next page in this series, as they expand on the general theory of rehabilitation. In a post on malady, I also draw a parallel between a sustained physiological imbalance leading to sickness and a sustained imbalance in biopsychosocial homeostasis leading to malady; I will explore this in more detail in future. The MindMap below summarises the ideas on this page.
Table of Contents
Introduction
The significance of balance and equilibrium in life has been central to medical practice since Aristotle’s time (around 2,300 years ago) and probably even earlier. The humoral theory proposed that each person had four humours (meaning fluids): black bile, blood, phlegm, and yellow (or black) bile. These four humours needed to be in balance, with the specific balance being unique to each individual. They formed part of a more complex theory that combined Aristotle’s four elements with Galen’s four humours.
Balance is also central to the Yin-Yang theory that underpins much of Traditional Chinese Medicine. Yin-Yang seems to apply to all aspects of health, both physiological and psychological, and possibly to work-life balance.
The importance of mechanisms to set and maintain constancy in some parameters is more recent. Dennis Bernstein gives a fascinating description of Feedback Control: An Invisible Thread in the History of Technology. One of the early mechanical mechanisms related to timekeeping, a verge-and-foliot mechanism that controlled the rotation of an axle, was developed around 1283.
It was 500 years before the next significant automated feedback control mechanism was developed. This was the governor, first described in 1788. The steam engine was the crucial need driving this invention, but it was also used in applications such as waterwheels, windmills, and phonographs. During the nineteenth and twentieth centuries, feedback mechanisms were developed across many technologies.
Homeostasis: early scientific history.
In July 1929, Walter B. Cannon examined the historical development of ideas about feedback control in humans, and I have selected a few examples from his paper. The recognition of biological feedback mechanisms dates back to 1877 when EFW Pflüger stated, in German, “The cause of every need of a living being is also the cause of the satisfaction of the need.”
Similarly, in 1885, L Fredericq said, “The living being is an agency of such sort that each disturbing influence induces by itself the calling forth of compensatory activity to neutralize or repair the disturbance. The higher in the scale of living beings, the more numerous, the more perfect and the more complicated do these regulatory agencies become. They tend to free the organism completely from the unfavorable influences and changes occurring in the environment.”
Claude Bernard, a French physiologist, set out the crucial importance of a stable internal physiological state in 1878, “It is the fixity of the ‘milieu interieur’ which is the condition of free and independent life,” writing a few pages later, “all the vital mechanisms, however varied they may be, have only one object, that of preserving constant the conditions of life in the internal environment.”
In 1900, C Richet, a Frenchman, summarised matters succinctly: “The living being is stable.” This page considers how stability is maintained.
Homeostasis
The term homeostasis was introduced by Walter Cannon in 1926, combining the Greek words homoios, meaning ‘the same’, and stasis, meaning constancy (not a fixed static state, but a fluctuating state that is kept constant). As George Billman stated, it refers to “the self-regulating processes by which a biological system maintains stability while adapting to changing environmental conditions.”
In their article, A physiologist’s view of homeostasis, Harold Modell and colleagues give five critical features that any homeostatic system must have:
- A sensor to measure the regulated parameter,
- A mechanism to determine the set point, the value of the controlled parameter that the system should achieve and maintain. This value may change.
- An error-detection mechanism to detect the discrepancy between the set point and the observed value,
- A control mechanism that uses the measured discrepancy to produce outputs needed to return the variable’s value towards the set point.
- Effector mechanisms that can enact the changes needed.
The homeostatic process remains constantly active, even when the system is stable and at its set point.
Homeostasis originated in physiology and is typically linked to it. However, the mechanism and ideas are universal. Keeping a stable condition, fluctuating around an average in response to changes inside or outside the system, happens in many areas, including biology, social structures, populations, finances, and more.
I have, before now, underestimated the importance and scope of homeostasis. For example, we have a physiological system to regulate our body temperature through shivering or sweating. However, if these mechanisms are insufficient, we will alter our behaviour. We might take off or put on clothes, light a fire, open a window, move into the shade, and so on. All these behaviours are partly automatic and serve to maintain our body temperature. Our biochemical environment also depends on food and fluids. A drop in blood sugar or dehydration, signalled by feelings of hunger or thirst, will alter our behaviour.
Thus, our vital physiological homeostasis depends on more than just an internal, biochemically mediated process. It also requires behavioural changes, and most homeostatic mechanisms influence our behaviour.
Biopsychosocial homeostasis.
Behavioural responses to physiological needs are fundamentally an extra homeostatic mechanism. However, most behaviours are motivated by physical, social, or psychological needs. For instance, I dress suitably for the dinner party I am attending, paint a wall to alter its colour, or cook food to eat. Many people have numerous needs they aim to satisfy, with Maslow’s hierarchy of motivational needs being a well-known classification.
The idea of balance in life becomes most evident when talking about work-life balance. However, many people do not work, yet everyone, including children, needs to find a balance. Furthermore, a division between work and non-work often does not apply in many situations. For many individuals, especially women, the domestic responsibilities at home reflect the demands of work, leading to an unbalanced life where too much time is spent attending to others’ needs and too little time is left for their own.
The question is, how do we prioritise our activities amidst competing needs? Should I go to work or attend my son’s graduation ceremony?
In 1942, John Fletcher authored an article on Homeostasis as a guiding principle in psychology; he covered several aspects of psychology in his work, including perceptual constancy and a person’s status, both physiological and social.
In 1962, George Engel published Psychological Development in Health and Disease, and in it he wrote, “When adaptation or adjustment fail and the pre-existing dynamic steady state is disrupted, then a state of disease may be said to exist until a new balance is restored which may again permit the effective interaction with the environment.” And, in 1966, Radhakamal Mukerjee suggested homeostasis was widespread across many domains of human society.
The early authors did not explore the mechanisms. In 1985, Alex Michalos published his Multiple Discrepancies Theory (MDT), available on ResearchGate. The theory suggests that people aim to optimise their net life satisfaction.
He has six hypotheses, but the main two are.
- Reported net satisfaction depends upon perceived discrepancies between a person’s present situation and what:
- they want,
- relevant others have,
- the best they had in the past,
- they expect in the next three years,
- they hope to have, after five years,
- they think they deserve and need.
- Pursuing and maintaining net satisfaction motivates people, and the drive is proportional to the perceived benefit.
Subjective well-being, a concept close to net satisfaction, is closely related to how well Maslow’s five areas of human need are met. (See: Needs and subjective well-being around the world.)
In summary, the concept that people strive for and maintain a stable equilibrium within limits in all areas of their lives has been repeatedly proposed over many years. While this does not prove the theories are correct, it does support further exploration.
Biopsychosocial homeostatic processes.
We have established that long-term stability in fluid and nutritional balance is maintained by behavioural changes, and similar mechanisms apply to body temperature. These needs are driven by intermediate urges such as perceived feelings of thirst, hunger, or cold.
We experience other needs, though with a less urgent imperative to act. For instance, we may feel lonely, bored, that others do not value our status, or that we require a higher income to feel secure. All these feelings can lead to a conscious change in behaviour.
In his General Theory of Behaviour, David Marks develops, with evidence, the concept of biopsychosocial homeostasis. He proposes that a central homeostatic neural network establishes the set points (targets) for various needs and monitors the discrepancy between actual status and these set points. It adjusts behaviour to minimise these discrepancies. There is some evidence supporting this theory.
Brian Edlow and colleagues studied six healthy individuals and identified neural networks connecting the brainstem and forebrain, especially the medial temporal lobe. This could be part of the Central Homeostatic Network. At this stage, the existence of a structural network cannot prove its function, but it does make the hypothesis plausible.
Sheri Mizumori and Yong Jo extensively reviewed the evidence in 2013. They proposed that the hippocampus played a crucial role in adapting behaviour by comparing actual and expected outcomes. The discrepancy worked through other networks to preserve stability.
Gillian Matthews and Kay Tye studied social homeostasis, specifically in rats exposed to acute social isolation, focusing on the avoidance of loneliness. They review how social isolation is detected and responded to.
They also examined the attributes of a social homeostatic system. Firstly, the social system must be adaptable, taking into account other demands, such as hunger, which may take precedence. Secondly, it might share its processing with other homeostatic networks or operate as a dedicated network; the former would help in prioritising tasks. Thirdly, they suggest that the subjective feeling of loneliness may be essential to signal a state that threatens health (see blog post on loneliness) and to enable the individual (rat or person) some degree of control. Fourth, they discuss valence, specifically the issue of positive or negative motivational drives.
Their theory was expanded to cover chronic conditions, such as long-term social isolation, by Christopher Lee and colleagues. Karen Bales and colleagues have examined the model, discussing how many factors influence each individual’s set point.
Emotional homeostasis has also been examined. John Montgomery has authored a theoretical article reviewing the evidence for emotional homeostasis and speculating that some mental health issues stem from homeostatic mechanisms that evolved to respond to natural events in the environment, which can be inappropriate in modern settings.
The mechanisms that maintain emotional stability may rely on autonomic changes linked to emotional states. Kenji Kanbara and Mikihiko Fukunaga explore this hypothesis. Coincidentally, in the same year (2016), Irina Strigo and Arthur Craig published evidence from studies on both monkeys and humans. They identified relevant neural pathways and observed expected changes in the insular and cingulate cortices in humans subjected to experimental manipulation of homeostatic processing.
In summary, plausible homeostatic mechanisms exist in humans and animals to maintain social and emotional balance. All such mechanisms operate by influencing an individual’s behaviour.
Synthesis
Humans, like other living beings, strive to maintain stability. Although this is most apparent in physiological functions, the principle is universal. Within acceptable limits, stability is upheld by a feedback mechanism that responds to deviations from the desired goal by reversing the change. This concept applies to mechanical systems like steam engines, electronic systems, and biological systems, where it is known as homeostasis.
In humans, physiological homeostasis has been thoroughly studied. The functions being regulated are vital to life; significant deviations might cause death, and the mechanisms are rapid-acting. However, many other essential aspects of a person pose fewer immediate threats to life and substantially influence well-being or quality of life. These responses are much slower but tend to last longer. They mainly involve behavioural changes.
Furthermore, stability can be sustained by modifying the target, whether it is the controlled phenomenon or the setpoint level. This differs from physiological parameters, where the target level remains fixed.
Detailed studies of the neurological mechanisms in humans and animals are still in the early stages. However, it is clear that such mechanisms exist and that constructs like social interaction are subject to homeostasis. Additionally, there is evidence that changing the set point or phenomenon of interest occurs in people. Further research should facilitate the development of more effective rehabilitation interventions.
The figure below illustrates how biopsychosocial homeostasis might function. Needs could be organised according to Maslow’s hierarchy, but the outline is generally applicable. The top third covers the most basic level system, related to each specific goal. The middle third shows that all goals related to needs must be prioritised, with some needs being delayed, modified, or abandoned. The bottom third proposes mechanisms that help maintain a sustainable balance.
Conclusion
Living organisms seek stability. Events disrupt stability. Consequently, living organisms have developed mechanisms to respond to change and restore equilibrium. This is the fundamental principle of homeostasis, which is well-established in bodily physiological processes. Bodily homeostasis must function within short timeframes, whereas most other parameters require longer periods. Physiological mechanisms are entirely internal, while all other mechanisms involve the organism interacting with its environment, including other beings. The concept of homeostasis has been extended to many aspects of human life and even to complex behaviours in animals. Evidence suggests that complex phenomena, such as social interactions, are subject to homeostasis. Therefore, it is reasonable to believe that most elements of a person’s life are governed by a homeostatic process, one that can be influenced consciously but does not rely solely on active control.