What
About Physiology?[1]
Andres Soosaar
http://biomedicum.ut.ee/~andress
Department of Physiology,
Intro
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[2]
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.
People
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.
Theoretical framework
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
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[4].
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.[5].
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.
Methodological considerations
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 (
Modern physiology is
characterized by 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 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 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 pendulum will clearly be on
another side. To my mind most of 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?
October 2004
References
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.
[1] 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 .
[2] Physis
may mean both essence and physical environment, therefore we can
construe at least two lines
of development for 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
[3] 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.
[4] 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.
[5] 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.