> You might ask whether selfishness and competition plays a role in
> our bodies. Of course we are familiar with the ultimate selfishness
> that occurs in a cancer when a cell reproduces excessively, but this
> is a harmful state. Are there systems which rely on competition to
> work properly?
I think parts of the immune system might be doing it, as different
antibodies both attack each other, forming weird epistatic networks of
mutual excitation and inhibition (which may or may not be important
for immune system memory - the jury is still out). There is also a
kind of competition between B cells about who gets to divide depending
on how well their antibodies fit an antigen.
In the brain, there are a lot of competition between cell groups, as
they mutually inhibit each other but excite themselves. Hence a
stimulus will lead to a competition but bias it towards the group that
responds the most to the stimulus, making it win eventually. This
appears to occur in many parts of the cortex and basal ganglia, and
underlies things like perceptual rivalries and decision making. In the
spinal cord such competition appears to be part of central pattern
generators creating rhythmic motions like walking or swimming. In
addition, there is a bit of competition among synpases about being the
"best" synapse to activate the postsynaptic cell - the best will grow,
while less efficient synapses might disappear.
Pattern formation is in general also a competitive process, as
different cells exude morphogens trying to influence their neighbors
to differentiate in one way or another or attract growing axons from
the nervous system. The structure of local blood vessel networks are
likely set by a competing process where different parts of tissue
demand oxygen and nutrient, and the parts that signal the loudest get
Competition is everywhere in the body, it is just that the system is
tuned to make it produce beneficial results.
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