Theoretical Models for Thermoregulation in Man
269
by efferent neural pathways; these controller outputs in turn act upon the
controlled system in a number of locations which are not necessarily
identical with the locations from which the temperature signals arise. This
arrangement can be schematically represented as in Figure 4. The completed
system is of such complexity that intuitively only qualitative estimates of
input-output relationships are possible at best, and quantitative estimates
are out of the question.
T
'a
Work
;
!
I
r-----l [,~---'-------,
i
\
Ta
1
J-t-'~~l- _J
:
- - - - - - -:--;- - - - - - \ - -
I
I
I
\
1
1
I
\
I
I
\
L------II ,---I ----,I '---I~ ~_ ---'--,--1
1
L ________ J
L _____________________ J
Fig. 4. Schematic diagram of multiple feedback loops. Heavy lines: components
or actions of controlling sYstem, light lines: controlled system, broken lines:
signal pathways
If the controlling system is efficient and effective, the expectation is that
a disturbance will result in counter-action without any of the temperatures
showing much displacement. The small displacements which do occur are
almost impossible to interpret because of the multiple connections: a given
relationship between a temperature displacement and a controller action is
first as likely to be fortuitous as real. The reason for this of course is found in
the strong connections between the various temperatures via the passive
links, especially in or near steady states.
There is only one way to further our knowledge of the thermoregulatory system: by breaking the strong and multiple connections in such a
way that isolated parts of the controller can be examined. This can be
accomplished by studying the effects of strong transient disturbances in
the dynamic phase during which strong links can be temporarily disconnected, or by opening one or more of the loops. In man, the study under
dynamic loads is the most suitable; while in animals it is usually possible to
open one of the loops. In either case, an exact knowledge of the dynamic
responses in all parts of the body is essential since neither approach is use-
269
by efferent neural pathways; these controller outputs in turn act upon the
controlled system in a number of locations which are not necessarily
identical with the locations from which the temperature signals arise. This
arrangement can be schematically represented as in Figure 4. The completed
system is of such complexity that intuitively only qualitative estimates of
input-output relationships are possible at best, and quantitative estimates
are out of the question.
T
'a
Work
;
!
I
r-----l [,~---'-------,
i
\
Ta
1
J-t-'~~l- _J
:
- - - - - - -:--;- - - - - - \ - -
I
I
I
\
1
1
I
\
I
I
\
L------II ,---I ----,I '---I~ ~_ ---'--,--1
1
L ________ J
L _____________________ J
Fig. 4. Schematic diagram of multiple feedback loops. Heavy lines: components
or actions of controlling sYstem, light lines: controlled system, broken lines:
signal pathways
If the controlling system is efficient and effective, the expectation is that
a disturbance will result in counter-action without any of the temperatures
showing much displacement. The small displacements which do occur are
almost impossible to interpret because of the multiple connections: a given
relationship between a temperature displacement and a controller action is
first as likely to be fortuitous as real. The reason for this of course is found in
the strong connections between the various temperatures via the passive
links, especially in or near steady states.
There is only one way to further our knowledge of the thermoregulatory system: by breaking the strong and multiple connections in such a
way that isolated parts of the controller can be examined. This can be
accomplished by studying the effects of strong transient disturbances in
the dynamic phase during which strong links can be temporarily disconnected, or by opening one or more of the loops. In man, the study under
dynamic loads is the most suitable; while in animals it is usually possible to
open one of the loops. In either case, an exact knowledge of the dynamic
responses in all parts of the body is essential since neither approach is use-