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Homeostasis refers to the principle by which the internal environment of the body is kept in a state of equilibrium by a multitude of fine adjustments at a hierarchy of levels ranging from the molecular level to the level of the organism as a whole. Claude Bernard (1865) first described what he called the ‘internal milieu’ and showed that this internal environment was ordinarily maintained within fixed limits. Walter Cannon (1932), in The Wisdom of the Body, coined the term ‘homeostasis’ for the coordinated physiological processes by which an organism maintains an internal steady state. Both Bernard and Cannon focused almost entirely on physiological homeostasis. Curt Richter (1942) expanded the idea of the protection of the internal milieu to include behavioural or ‘total organism regulators’. From this viewpoint, behaviour lies on a continuum with physiological events. Richter combined the perspective of Bernard with that of Cannon and he added behavioural regulation.

Behaviour, for Richter, was broadly conceived to include all aspects of identification, acquisition and ingestion of the substances needed to maintain the internal environment. The current theory extends the homeostasis concept one step further in suggesting that not only feeding, but all human behaviour, follows the principle of homeostasis. Psychological homeostasis is best explained in two stages, starting with the classic version in Physiology, followed by the new version extended to Psychology. Physiological homeostasis is illustrated in Figure 2.13.

There are five critical components that a regulatory system must contain in order to be counted as homeostasis:

1 It must contain a sensor that measures the value of the regulated variable.

2 It must contain a mechanism for establishing the ‘normal range’ of values for the regulated variable. In the model shown in Figure 2.13, this mechanism is represented by the ‘Set point Y’. Arguably, the term ‘set range’ would be more appropriate than ‘set point’.

3 It must contain an ‘error detector’ that compares the signal being transmitted by the sensor (representing the actual value of the regulated variable) with the set point or range. The result of this comparison is an error signal that is interpreted by the controller.

4 The controller interprets the error signal and determines the value of the outputs of the effectors. In the vast majority of cases, the controller is an automatic, nonconscious process.

5 The effectors are those elements that determine the value of the regulated variable.

Figure 2.13 A complete representation of physiological homeostatic mechanisms (adapted from Modell et al., 2015)

We turn next to consider psychological homeostasis. Identical principles to those described above for physiological homeostasis apply to the regulation of behaviour and experience (Figure 2.14). For psychological homeostasis, however, the internal effectors remain active but the boundary between the internal and external environments lies between the controller and the outward effectors of the somatic nervous system, i.e., the muscles that control speech and action.

Figure 2.14 A complete representation of psychological homeostatic mechanisms (adapted from Modell et al., 2015)

Let us consider how psychological homeostasis works in practice. All people are oriented towards seeking and/or preserving physical and subjective well-being at a set point that is kept at the highest possible level. Hence, we tend to approach new resources in the hope of finding a reward for this behaviour and equally to avoid punishing or confrontational situations. If we do encounter threat, our behavioural options include either ‘fight or flight’ or inhibiting our behaviour so as to go unnoticed and to avoid confrontation. One can easily imagine the adaptive value of behavioural inhibition. A mouse scurrying through the grass suddenly notices a buzzard flying overhead. Out of fear, the mouse freezes, thus avoiding attracting the buzzard’s attention. Playing dead until a predator has passed can be beneficial, as long as the tension of waiting does not have to go on for too long. Figure 2.15 shows a homeostatic strategy for choosing optimal behaviours and the brain structures that may be involved in the process. The diagram shows the feedback loops whereby our memories associate positive or negative connotations with situations that we experience, and then guide behaviour the next time they arise.

Figure 2.15 Approach and avoidance behaviours that maximize well-being

Source: Copyleft, http://thebrain.mcgill.ca

Life isn’t always this simple, however. The whole process could fall apart if you’re not a mouse hiding from a buzzard but, for example, you’re a worker dealing with an exploitative boss. The worker cannot fight or flee, or they would be out of a job. So they can either join a labour union and talk to the union representative or they can let months and years go by while they inhibit their behaviour. This ‘do-nothing’ strategy ultimately can have disastrous effects on their health. For one thing, such inhibition causes hormonal changes that produce high blood levels of glucocorticoids, whose depressive effect on IS function is well known. This weakening of the IS is why remaining in a prolonged state of behavioural inhibition can cause all kinds of health problems.

One source of inhibition is our imagination – our fear of failure. This can lead us to foresee so many potentially negative scenarios that we end up doing nothing. To do nothing, and to maintain a dream, may be a better option than to act and to fall flat on one’s face. Whichever way one looks at the issue of inhibition, it has an obvious connection with homeostasis, a striving towards equilibrium.

Initiated by the brain, homeostasis also can act in an anticipatory mode. The preprandial (prior to having a meal) secretion of insulin, ghrelin and other hormones enables the consumption of a larger nutrient load with only minimal postprandial homeostatic consequences. When a meal containing carbohydrates is to be consumed, a variety of hormones is secreted by the gut that elicit the secretion of insulin from the pancreas before the blood sugar level has actually started to rise. This starts lowering the blood sugar level in anticipation of the influx of large quantities of glucose from the gut into the blood. This has the effect of blunting the blood glucose concentration spike that would otherwise occur. The relevance of psychological homeostasis has been underestimated in the study of behaviour, health and illness. In this book, psychological homeostasis is given its rightful position at the ‘hightable’ of psychological constructs.