The human body is a complex system. It has a natural ability to grow and
develop over time, as well as adapt to the frequent changes in the surroundings. The
complexity associated with it and the various processes it undergoes lie in its structure
and functionality. Complex chemical reactions play a central role in the evolution of
structure and organization of this complex adaptive system, which are inherently
directed along the paths of maximum entropy production. Entropy production causes a
system to degrade itself by the gradual consumption of free-energy to a more
thermodynamically-stable state. However, the human body, and open systems in
general, have a tendency to preserve or increase order and complexity with time. This
phenomenon of spontaneous appearance of order is known as self-organization. Thus,
the human body has a structure and several underlying functions that give rise to
organization. Simultaneously, it prevents the destruction of this state of organization by
self-organizing itself with time. In the following chapter, we will look into the details
of (self) organization from a physical and an information perspective, in order to see
the relationship between complexity and the growth in organization of a system with
time. Further, understanding the concept of (self) organization from a functional
perspective is also important as it will allow us to relate metabolic reaction-sets to
structural symmetry, metabolites to interacting nodes, and mapping these interactions
into complex networks. Finally, our aim will be to relate ageing to the loss of energy,
information, organization and functionality of the human body with time.
Keywords: Complexity, Dissipative Systems, Principle of Least Action, Second
Law of Thermodynamics.
