The study of life is an old intellectual enterprise of humankind and the question “What’s going on with me and others, who are similar to me?” was probably among first questions which raised human curiosity. At the beginning those similar objects were other human beings but later on the area of relatives in having life had become wider and wider until realizations of modern modified cellular life and different forms of truly artificial life. The ‘What’s going on?’ question quite truly describes the main task of physiology. Physiology is by itself a very old field of science which has been several times changed its paradigm during history. With time its scope has become narrower and narrower but is still enormously big. Through all times another basic question for physiology has been “How the ‘What’s going on?’ fits into the world supposed to exist with and around of us?” This question has several possible lines for answer: (i) there are processes which are the processes of life, (ii) the necessary material fitting needs steering and regulation of the processes of life, and (iii) how (i) and (ii) fit to our theoretical picture about world. Let’s focus later on the attention to very recent period of physiology and try to find think of some trends which may have any meaning in the further development of the field. Yes, we are speaking about time of the last quarter of 20th century, when biochemistry and biophysics have already decades ago left physiology, and cell biology and neuroscience are doing the same. Many important things have happened that time: among others permanently increasing amount of empirical knowledge and techniques which forces people more and more to specialize to small pieces research without any special holistic cares; computer revolution in information processing and management; very rapidly increasing list of methods to manipulate on the level of genes and other tiny ones and tremendous amount of empirical data from using of those methods. Sometimes we feel that there is time for the completely new physiology and it may sometimes disturb our reality sensing, because instead of us the object of the field has almost not changed. Of course, human physiology feels itself in such condition not very well, because the human being should be simultaneously not changed and changed, and due to the elementary logic it is an impossible task to complete.
Physiologists are a special sort of people and very good guys: most of them are optimistic, open minded and to certain extent not too rigid. Many of them have at least moderately holistic way of thinking, but they turn to be quite strict when talk is about ways to get new knowledge. Physiologists are people of empirical and experimental knowledge, only these are right gates to get open right understanding about nature of life. They mostly trust facts but sometimes indeed, they allow temporarily hypnotize themselves by charming hypotheses or rather universal theoretical constructions. You may notice some paradox here, how to combine concrete experimental conditions and holistic thinking how things of life are to be. They don’t trust too much the pure theory, they always ask empirical confirmation for their theoretical constructions. It that sense many physiologists are quite critical to modern views on life as implementation of certain common logic, despite of real matter and structure in what life is realized. They like to accept the supremacy of ordinary biological life and take any other possibility for life simply as a partial possibility of the true life. This attitude is so strong that people who usually propagate those modern views about life come from philosophy or other fields of functionalism which don’t have too strong connections to typical cellular life.
Physiology as any other natural science is very much synthetic; it tries permanently to improve the existing physiological pictures with new empirical facts and not so much to deduct new possibilities from laws of physiology. Reason for this is quite simple, there are very few such laws providing possibilities for deduction. In fact they clearly believe in the physical and chemical nature of the living and it gives them chances to derive something, because laws of chemistry and physics must work always properly. Along the synthetic line physiologists like so much different models and analogies which they take as supporting factors to theoretical constructions. Existing models also give a possibility to predict possible physiological events and real values of certain variables.
But without any doubt some notions and concepts are fundamental to physiology. Surely ‘process’, ‘function’, and ‘mechanism’ are among the most important categories of the field. They are so basic that members of the guild doesn’t discuss on the meaning of those words and use them intuitively in appropriate context. Furthermore, these terms work very well at any level of biological organization and present certain dynamic nature of events and chains of events corresponding to life. The ’process’ is the least defined nominator for events happening in organism. Huge amount of different things happen every moment in whole organism or in a part of under investigation, but only some of them serve attention of a physiologist. A certain set of events collected in a certain way be called as the ‘physiological process’. Those events are physical, chemical or social or informational and may happen in space with very different size. Just proteins are special in a sense that they are able to exert simultaneously and spatially very close to each other all 4 types of features. Important moment in the process seems to be the serial order of events or sometime some other way of organization. Another important feature of physiological processes is their flexibility to be realized with different magnitude or intensity. In fact both aspects reflect the possibility of living matter for certain, but not totally rigid, organizational properties.
For the next, some combinations of processes may pretend to be the ‘physiological functions’. Here we meet 2 problems which have hardly digestible to modern scientific cognition. The first one is the question about teleology. Since Darwin the concept of teleology has lost a lot of its previous reputation but physiology is still widely using the way to explain things and processes via goal or function, e.g. the goal of physiological processes in the lung is to guarantee adequate gas exchange between air and blood. Thus, the function seems to be a sort of coupled processes, and also a way to organize different processes. Functions are characterized with temporal stability and certain pattern, most of them exist as long as life is there in organism. Life and functions are so closely connected that some people say that life is a set of physiological functions. There are several more or less traditional or objective ways to classify functions. Marie Francois Bichat once (~1800 AD) distinguished the vegetative and the animal functions. The Darwin’s historical contribution to physiology was the idea of adaptational nature of physiological function, it became instead of God a new universal goal of organism functioning. Surely there are more possibilities to group functions, e.g. to separate structural and informational functions or cellular and supracellular functions etc. Such plurality of classifications brings us immediately to another problem with functions. Are those different physiological functions genuine ones or only manifestations of our cognitive imperfection? At first glance the second possibility seems more probable, as different divisions simply focus on different aspects of the complexity of life.
An interesting set of functions is connected to consciousness and other mental capacities. Physiologists have not found any problems with ontological basis of consciousness and are sure that nerve cells produce all those mental activities. A big exception was Sir John Eccles, but his dualism was also connected in a special way to processes in nerve cells, despite of possible traps of cellular dualism. Consciousness is an arena where meet different sorts of information from different sources and certain unified output will be produced. In humans consciousness has in addition to older possibilities obtained tools of formal languages as universal currency for information unifications. This adds to the biological existence a new dimension which gives to human society more possibilities realize itself and make them more open-ended enterprises. At the same time some of these unifications, e.g. money as a measure of social contract, may influence in quite unexpected and unwished way to members of society.
Altogether, in modern times functions as explanatory tools are widely used and therefore physiology as a general science of functions may be connected to almost any other field of human intellectual activity.
The third important notion in physiology is the ‘mechanism’. In other words we may say that mechanism is the design of function. Usually the question about the designer is left aside and we wonder only design of certain function or phenomenon. The leading principle of design in physiology is causality. When we think about cellular functions, the physical and chemical causes are the main players to realize certain set of processes in real space-time situation. Causality serves like ultimate reason for something to happen or not. At the same time probability is also widely used in common cognitive format of physiology. As general, probability has different roots to appear: one is natural uncertainty which makes probability to absolute category, another line is more relative and depends on our level of knowledge. To be the causality fundamentalist is to believe and follow the idea that all probability is relative and there are possibilities to lower and finally remove uncertainties. Thinking about evolution, we can take it as a function of supraindividual life and hold along the Darwinian natural selection as a mechanism of evolution. But how about causality and probability in this case? Changes in environment seems to save both causality and probability and don’t force us to accept rigid determinism in the biological world.
Another, more specific, element of physiological design is the notion of threshold. Different thresholds serve as the lowest breaking points where behavior of a system clearly changes and becomes somehow more physiological, i.e. be in a range of optimal conditions.
Being equipped with categories, let’s move on to theoretical frameworks and theories. The most important theoretical framework is concept of homeostasis. Claude Bernard’s milieu interieur and Walter Cannon are main creators of the concept and no doubt the homeostasis governs almost all orthodox physiology and not only physiology, the concept plays an important role in many other sciences which focus themselves to behavior of systems. In ontogenetic context homeostasis is something more as a process, an ordinary function or a mechanism, it is a complex set of them. With homeostasis we see again obvious teleology connotation of physiology, because an A-B-C truth of physiology says that a goal of body functioning is to hold homeostasis. In this point there is a possibility to classify homeostasis as a feature or the whole organism function indeed, and not take it as a theory. Homeostasis is about spaces which are filled with environment, having it and getting it promises stability of immediately surrounding environment to the elements of systems (cells in case of natural life) and to whole system (organism) earn more and sometimes risky and energetically more demanding possibilities to survive in surrounding. In wider ontological context homeostasis works as a structure making device, where more homeostasis means more levels and more selectivity barriers between them. It makes a system more structurally complicated and may potentially give a basis for more complicated behavior. Thinking about cellular life, you may take it as a difficult multilevel set of membranes which offers certain stability already on the suborganellic level. Selectivity barriers seem really be universal design of this world, think for example about different artificial spaces or ‘cells’ (houses and apartments, several different transport vehicles etc), all they provide and help to hold certain specific properties in comparison to external environment. The social systems and societies are also able to create selectivity barriers and build up multilevel structures to get the bigger variety of behavior in different situations. But there is not enough to hold homeostasis only with borderline selectivity barriers, some organizational efforts should also be made to hold the situation more permanent. Physiology has many explanatory items to describe those organizational efforts. Different metabolic and regulatory pathways serve all to create an stable environment inside of the selectivity barrier. Despite of the bias to teleology, physiology doesn’t usually ask why-questions, it likes how-questions and leaves the whys to philosophy of biology and metaphysics.
What is it necessary to do to be a physiologist? You need to hunt for unknown processes, functions, and mechanisms in living systems. You need to do experiments, get results from those, put the results to the existing hypotheses, and formulate your result and positions in accepted cognitive formats.
Physiologists like to manage with systems. Yes, at first the goal was to understand organisms, but now they hold that it is possible to see physiological processes everywhere in organism and often the wish is to study them both individually (as autonomous units of organism) and in interaction with other processes and functions. The concept of system is very convenient and flexible in this sense and provides possibilities to restructure existing processes and sets of them in numerous ways. Another very important component of the physiological approach is the measurement, i.e. empirical quantitative estimation, of the physiological event or process. This is the real basis for certainty in physiology. Sets of measurement results in different situations and conditions are the true physiological facts on what we can with structural support construct the physiological reality. It may seem quite simple, it is necessary only to measure something in certain point of space, but real situations are much more difficult on both technical and biological reasons. There are real problems and difficulties to measure something in living structures in functioning due to the size a zone of interest and influence of measurement itself to natural processes. It may be so difficult that in many cases there is impossible directly study the issue in in vivo conditions. There are also increasing ethical requirements which can limit or forbid existed and existing physiological methods. The direct vivisection is a good example of this trend and is nowadays truly not allowed. An alternative way is to study processes in in vitro conditions but for body functioning you get only orientation and not final certainty how things really running in organism. In modern times people speak a lot about experiments in in silico conditions, but this way also needs physiological facts and models, otherwise it doesn’t explain anything about real biological functioning. Computers have been very much involved to appearance of new field – the artificial life (AL) studies. In fact there are two younger sisters in the family of the human made ones or artificiality, a bit older and more known is the Artificial Intelligence (AI). Sometimes two sisters want to study both life and mind as a sort of software which have ability to be run in different material systems. Here we meet a chance for pure functionalism, a pure dynamic form, without specific support from matter. A good critical example of such vision is presented by Margaret Boden (1999) who asks rather rhetorically “Is metabolism necessary?” Her answer is positive, but such set of question is badly digestible for typical physiologist mind. Despite of the importance of functions, the mainstream physiology seems to be married to real biological structure and real life is the complex interaction of structure and function.
Modern physiology is characterized by the strong focus on processes on the level of genes and early processing of proteins. Only some 30-40 years ago genes were only units for heredity, but now we know that genes are much more dynamic items which permanently control different activities of cells during their life. Many difficult cellular responses are blueprinted on the level of genes and their networks and their realization is modified by different environmental factors. Physiology is here in the phase intensive data collection of processes and interactions on quite bottom level of biological organization. We can see on this level exactly those crossroads, where universal scenarios give individual versions which finally result with the great variety of phenomena and processes on the organismic level. At the end of this phase, the new generalizations about material basis of life should necessarily appear.
Altogether we see and have to accept the selectivity of physiological approach and this in its turn rationally limits possible achievements of physiological approach, increasing their certainty.
A possible scenario for future
As mentioned at the very beginning, physiology is an old field with several curves in its development. Let me imagine only one very general road for future physiology. It is useful to remember again two basic biases of the field: one is the study of individual dynamic processes themselves and another is the pursuit to catch a logic of those processes and their complexes. I’m quite sure that it is impossible to avoid those biases, vice versa, we must carefully support them because they produce the space for the intellectual achievements of the field. Physiology now is clearly and quite extremely biased to the discovery of new individual processes, but this only matter of time when the pendulum will clearly be on another side. To my mind, most of the physiologists have indeed their final hope in the field to see what is behind facts and processes. Who knows, it may happen that we will see soon the meeting of modern versions of Aristotelian physics and metaphysics?
¤ Boden MA. Is metabolism necessary? British Journal for the Philosophy of Science, 1999, 50, 231-248.
¤ Mahner M, Bunge M. Function and functionalism: a synthetic perspective. Philosophy of Science, 2001, 68, 75-94.
 Being almost two decades a member of the physiology department with long history, traditions, and eminent physiologists you sometimes start to think about the field, physiology, and the party you are involved of .
 Physis may mean both essence and physical environment, therefore we can construe at least two lines of development of physiology. Current development of the field is mostly connected to life in physical environment, but essential explanations may indeed serve as a final goal of physiology indeed.
 Interestingly, evolutionary biologists and physiologists don’t understand each other very well. Maybe problem is in time scale, the first party thinks in the range of thousands and millions of years and the second party ususally measures time in seconds, minutes and hours.
 It is empirically is well shown that language based mind needs careful social download. Human being alone, in isolation from human environment, is not able to develop this capacity and must exist without linguistic consciousness. We may take whole process of education as a downloading of both software and some data for the brain as a highly specialised powerful computer. The brain-computer also contains more biological or cellular types of software and downloading of that is driven by genome and cell-environment interactions.
 Mahner and Bunge (2001) have offered this possibility very clearly and quite substantially. They differentiate at least 5 different concepts of function and functionality which work equally well in biological world and human society. Interestingly, philosophers much more care of exact notion of functions, physiologists mostly use the term and concept mostly intuitively.