Sleep is a field of choice, where tomorrow’s decisions are formed

 

Introduction: Sleep we notice only when it starts to speak up

Rejecting templates and shifting to a systems view

This book is about sleep, but it is not about the magical eight hours or familiar lists of prohibitions like giving up coffee after six in the evening. It is about how a person actually lives when we look at them not through the lens of separate organs or isolated symptoms, but as an integrated functional system of actions, decisions, and relationships. In such an architecture, every element serves a useful adaptive result, and sleep and wakefulness appear as two equal phases of a single daily cycle.

Two phases of a single life cycle

In the waking phase, our organism solves the tasks of interacting with the world in real time: seeing, acting, speaking, making decisions, and enduring demands. This is the period of active execution of outward‑directed functions. In the sleep phase, the same mechanisms, guided by the same Principle of Optimality, switch to another class of tasks without which life gradually falls apart. Deep metabolic cleansing takes place, along with structural repair, reorganization of synaptic connections, integration of daytime experience, and a careful retuning of how we will see ourselves, others, and our own future the next day.

The human being as a self-regulating living system

Our previous projects on biological rhythms, time and behavior, and on how people make decisions under load led us to a simple but demanding idea. To truly understand a human being, we have to see them as a living system that continuously regulates its course—from bodily functions to complex social relationships and long‑term plans. In this picture, sleep turns out not to be a technical detail or a pause, but one of the key phases of systemic regulation. It is here that it is decided whether the brain's internal forecasting apparatus—known in Pyotr Anokhin's Theory of Functional Systems as the Acceptor of Action Results (acceptor of results) —can form an accurate prediction for tomorrow, and whether we will have enough resources to act and feel in the way that our state of health requires. Throughout this book, we take this theory, together with the Principle of Optimality, as our basic framework for understanding how living systems regulate themselves day and night.

Sleep as the foundation of life strategy

If we look at sleep only in its separate dimensions—as rest for the brain, as hygiene, as a way to process accumulated information, or to discharge stress—we inevitably miss the main point. In many popular approaches to self-care, sleep remains just another habit alongside nutrition and exercise, instead of a full-fledged stage on which our tomorrow is shaped. In this narrow view, it looks like an add-on to real life, a technical pause between days. In this book, we start from a different assumption: sleep is a fundamental phase in regulating life as a whole. It is a special state of homeokinesis in which the processes of the body, psyche, relationships, and our life decisions are aligned and renewed.

A new lens for medicine and everyday life

Our exploration does not begin with a list of sleep stages or a comparison of gadgets, but with a larger systems question: how is human life organized, and what happens to this system when the mechanism of sleep fails. We will clarify why regulation is the main protagonist of this story, and why through such a lens sleep emerges as one of the central stages of our existence. It is the stage on which it is decided what our tomorrow will be like and whether we will have the strength to reach the places we truly intend to go. This shift of perspective forces us to reconsider everything—from prevention to the treatment of disorders. We stop fighting isolated symptoms and instead learn to support and retune living systems, on whose coordinated work the success of our life course depends.

Part I. Human life as a system of regulation (homeokinesis)

In this part, we will look at human life not as a static set of organs, test results, or medical diagnoses, but as a continuous living process of regulation. The central concept here is homeokinesis—the ability of a living system to preserve its integrity and chosen course not through frozen "stability," but through ongoing change, internal restructuring, and flexible adaptation to new conditions. This is a broad frame that includes ideas of homeostasis, adaptation, and stress responses, but views them from a single angle: how exactly the system keeps finding ways not to fall apart and not to lose the meaning of its movement. Step by step, we will introduce a language that allows us to describe not only current states, but also the logic of transitions between them. This will later help us see sleep as an active and critically important phase of overall regulation rather than as an empty "gap" in time between two days.

Chapter 1. Life as lived: what a human being actually has to regulate every day

A human life cannot be reduced to a list of passport characteristics or tables in a medical record. It is the continuous interaction of an open living system with the world, in which decisions have to be made and the life course continually adjusted from minute to minute. Body, psyche, and social ties do not exist in isolation; they form a complex system in which each element responds to the others. Our diet and the quality of our sleep directly affect our emotional background, and our emotional state, in turn, changes the character of our decisions and the quality of our relationships. At every moment, this system has to withstand external challenges and internal uncertainty, trying not to lose itself—that ongoing effort is what we call regulation.

The human being as an open dynamic system

If we look at a human being as an open system, it becomes clear that we are never fully isolated from the world. There is a constant exchange of energy through food and movement, of matter through breathing and biochemical cycles, and of information through sensing and communication. In this picture, stability does not look like a flat line of rest. In line with the Principle of Optimality, the system constantly searches for ways to distribute limited resources so as to reach its aims without unnecessary expenditure—a concept we have explored in detail for life, health, and disease at both individual and societal levels. This is continuous work: to strengthen some processes, to dampen others, and to swap priorities in order to remain alive and capable of acting. In later chapters of this part, we will return to this principle more directly and use it as one of the main tools for understanding how human life is regulated day and night.

Homeokinesis can be imagined as maintaining balance in motion—like walking over uneven ground. To avoid falling, you cannot freeze; you have to keep making small adjustments in body position. Life works the same way: from maintaining basic physiological parameters such as blood glucose or body temperature to complex social adaptations, the system searches for ways of acting that both allow it to withstand the present and do not cut off its future. This capacity for continuous reconfiguration and flexible response to change is the very essence of the living.

Spheres of everyday regulation and environmental challenges

In everyday life, we simultaneously inhabit several "layers" of regulation. The first consists of basic biological needs: sleep, nutrition, a sense of safety, and circadian rhythms. The second is made up of social expectations: roles in the family, professional responsibilities, and cultural requirements. The third involves our own inner goals and meanings, for the sake of which we are willing to endure everything else. Regulation consists in the ongoing balancing between these spheres: what is primary for me right now, what can be postponed, and what I will inevitably have to pay a price for.

Crisis conditions—prolonged stress, war, sudden losses—often break habitual adaptation schemes. What used to "hold" suddenly stops working. In such moments, it becomes especially clear that the quality of life depends on how regulatory mechanisms function. It matters which signals we notice and which we ignore, and how we form the acceptor of results—the inner image of what we truly expect from our actions. If reality constantly diverges from these expectations, the system can either flexibly correct its course or get stuck in a state of exhaustion, where sleep ceases to be a resource and becomes yet another zone in which we feel we are losing control.

A language for describing regulation and awareness of states

To avoid drowning in the chaos of events and sensations, we need a language that describes the internal logic of processes, not just surface labels like "tired" or "nervous." When we do not understand how our own regulatory loops work, everything happens chaotically and we merely register the consequences—irritability, breakdowns, or insomnia. Contemporary approaches invite us to see life as a sequence of closed loops: we perceive something, evaluate it, decide to act one way rather than another, obtain a result, and compare it with what we had hoped for.

From this perspective, sleep is not a passive "switching off," but a separate phase in the work of the same loops. During this time, connections in the brain are updated, information is processed, and energy resources are redistributed in line with the tasks of the coming day. The more precisely we can name our states and understand how they arise, the more chances we have to move from passively undergoing circumstances to actively steering the quality of our own lives. The very principles that help us withstand demands during the day also operate at night, maintaining the integrity of the system as a whole.

Chapter 2. How this regulation has been described: from reflex to homeokinesis

In this chapter, we will trace a path from the simplest ideas of “stimulus and response” to more integrated approaches that try to describe a living person in motion rather than in a frozen snapshot. We are not interested in the history of neuroscience for the sake of dates and names, but in the tools it gives us for understanding life regulation—and in why most of them prove insufficient when we try to explain a real human life course, including sleep.

From reflex to centers in the brain

The classical reflex model promised a very convenient simplicity: there is a stimulus, there is a response, and between them, a relatively direct path. Within this scheme, elementary movements and protective reactions were indeed well described, and it gave a powerful impulse to the development of physiology and neurology. When attention shifted to “centers” in the brain—the centers of breathing, sleep, or hunger—it became possible to link specific structures more precisely with particular functions, to build maps of “responsible zones,” and to understand better the consequences of damage.

However, this proved insufficient for explaining an integral act. A person rarely reacts linearly: the same stimulus at different times can evoke opposite actions, because what matters is not only the signal, but also the context, prior experience, current goals, and the relationships we are in. The model “there is a center – there is a function” turned out to be too flat for a living biography—and even more so for such multidimensional phenomena as chronic insomnia, nighttime awakenings in conditions of danger, or sudden collapse from fatigue in the middle of the day.

Homeostasis: a step forward that is still not enough

The concept of homeostasis was an important step toward recognizing that the organism constantly works to maintain internal balance. The focus here is no longer on separate reflexes, but on sustaining temperature, pH, glucose level, blood pressure, and other parameters within relatively narrow ranges. This made visible the everyday work of numerous regulatory loops and showed that life is not a passive state but an ongoing effort to keep balance.

Yet, if we look at a human life more broadly, the frame of homeostasis quickly becomes too tight. A real biography is not only a return to “normal,” but also going beyond it, learning, changing identity, and adapting to an environment that itself is constantly changing. A person does not simply restore the state of “as it was,” but is often forced to construct a new mode of existence in which old settings no longer work: after trauma or loss, in conditions of war, chronic stress, or prolonged exhaustion.

From homeostasis to homeokinesis

We therefore need a term that does not reduce health and resilience to returning to the same point. In this book, we use homeokinesis to mean the ability of a living system to preserve its integrity through continuous movement: to change configurations, shift between regimes, and rebuild connections so that it remains whole even when external conditions change radically. In this sense, the phase organization of life becomes crucial: daytime activity and nighttime sleep, periods of tension and recovery, crises and phases of relative balance, episodes of focused action and phases of digesting experience. The life course then appears not as small oscillations around a single “norm,” but as a sequence of regimes between which the system learns to move without self‑destruction. Within this frame, sleep ceases to be a mere return to zero and emerges as one of the main phases of homeokinesis—a time when the system retunes itself for the next segment of the path.

Networks, connectomes, and what they still miss

Modern network and connectome approaches have taken another important step forward: they have shown the brain not as a set of isolated centers, but as a system of interconnected networks. Researchers map structural connections, track synchronous activation of regions in different states—from deep sleep to focused attention—and identify the default-mode, attention, control, and emotion-processing networks. We see increasingly clearly how the configuration of connections changes with fatigue, insomnia, chronic stress, and depressive or anxiety disorders.

This is indeed a rich description of structure and connection dynamics. Yet, even the finest map of networks says almost nothing about what the organism is acting for, and why it chooses this course rather than another. One can know which nodes are connected to which and still not understand the logic of an act: why a tired person continues scrolling news until two in the morning; why, in danger, one person falls asleep amid chaos while another cannot sleep for weeks. A map of connections describes how everything is linked, but barely answers the question of what purpose the system pursues when it chooses a particular chain of events.

Why we need a different language

To speak of life as a process of regulation, we need a language that holds bodily, psychic, and social processes together and puts at the center not a separate organ or symptom, but a result that is useful for the whole system. Such a language must allow us to describe not only what happens inside nervous tissue, but also how these processes are woven into our relationships, decisions, habits, and routes by day and by night. In the following chapters, we will gradually move into this perspective, where sleep, daytime activity, choice of actions, and the capacity to withstand environmental blows are seen as different phases in the work of one and the same living system that seeks not merely to stay within a “norm,” but to preserve itself in motion.

You can learn more by reading our e-book 

Mykola Iabluchanskyi together with Andriy Yabluchanskiy