Biology Reference
In-Depth Information
The enormous complexity of thought processes and control actions makes the
CNS unique, where e.g. modern psychosomatic research shows how powerful
thought processes and emotions are in controlling bodily functions, resulting in both
positive and negative health effects
[29,31]
. This includes the fascinating data on the
placebo effects, for instance how cognitive activation with placebo analgesia engages
similar neuronal network as opioid analgesia
[32]
.
Recent development within the fields of genomics and molecular biology has
vastly increased the knowledge of the regulatory function at cellular and molecular
levels. However, among the many levels of organisation, the brain is unique; besides
obtaining all intrinsic information from the entire organism, where the amount of
afferent fibres is ten times as many as efferent ones, to which comes a range of blood-
borne hormone messages, the brain also receives continuous information about the
extrinsic environment via e.g. vision, hearing and olfaction.
The pathways from the brain to bodily expression can characteristically be divided
into previously mentioned efferent links: The somatomotor system, the autonomic ner-
vous system and the endocrine system. These triads of response patterns, organised at
the paleo-cortical-hypothalamic levels and principally equal in man and animals, are
phylogenetically very old. The terms “defence” and “defeat” reaction are derived from
their intense engagements in animal experiments. This may give the erroneous impres-
sion that they are reserved for catastrophe situations only, but actually, they are in mild
forms, and in various constellations, parts of daily life in modern society. Maybe one
of the best models to describe these two reactions is the one of “hawks” and “doves,”
describing how animals cope with stress with different behavioural strategies. Hawks
are the aggressive individuals with a fight and flight reaction strategy while doves show
freeze and hide behavioural strategies or outright withdrawal and defeat
[33,34]
.
11.4.1 Defence Reaction
The age-old defence reaction is, as mentioned, commonly induced in mild form in
modern society life, e.g. whenever man is exposed to interesting, irritating, or other-
wise challenging mental stimuli. When acutely induced, a differentiated sympatho-
adrenomedullary discharge increases cardiac output and blood supply to the skeletal
muscles, myocardium and brain, while blood flow and functions are reduced in organ
systems not needed for vigorous motor activity, e.g. kidneys and gastrointestinal tract.
As a net result, blood pressure is raised, usually to a considerable extent. The increased
secretion of adrenaline causes release of glucose from the liver that increases blood
glucose levels, while glycolysis is facilitated in skeletal muscles. Activation of the
sympathetic-adrenomedullary system also increases the release of lipids to the circula-
tion, boosts the coagulation system by e.g. facilitating thrombocyte aggregation
[35]
and stimulates the immune system in a different manner
[36]
. All these effects serve
as anticipatory adjustments to favour flight or fight and physical exertion. Enhanced
mental activity and alertness are also a common features of the defence reaction which
is partly due to increased blood-borne catecholamines.
At maximal engagement, this implies an all-out mobilisation of the organism's
resources to cope e.g. with life-threatening situations, were the gain of a split second
