Biology Reference
In-Depth Information
Living system
1
Comparison of the input
with the norm (=set point)
Assessment of deviations
from the norm
Decision-making for
restoring the norm
Instructions to effectors
for restoring the norm
1
2
3
4
2
3
4
Efferent output
Effector
mechanisms
State of
the system
Environmental agents
Figure 1.4 A generalized and simplified diagram of the integrated control system in
metazoans, with a central nervous system (CNS) acting as controller of the system. Metazoan
structure degrades continually due to intrinsic, thermodynamically determined causes,
as well as a result of adverse influences of the environment. Changes in the structure and
function of the organism and environmental changes are monitored by a pervasive network of
interoceptors and exteroceptors and communicated to the CNS. In the CNS, the afferent input
is compared to the neurally determined set points (1). Deviations from the norm are identified
(2), and pathways for restoring the norm are determined (3). “Instructions,” or commands for
restoring the norm (4), are sent to effectors (pituitary, target endocrine glands, or cells in target
tissues) through signal cascades. Via the molecular and afferent feedback input, the controller
receives continual information on the restored/degraded state of the system ( Cabej, 2012 ).
struggle against the hostile thermodynamic forces, but ultimately it will give in to
these forces after producing progeny and so forth, in recurring cycles of reproduc-
tion that enable the species to survive at the expense of the individual. Thus, a spe-
cies' existence is perpetuated by sacrifices of individual lives, or the species owes its
existence to the reproduction of mortal individuals.
Given the exceptionally high degree of the functional and structural complexity of
living systems, unrivaled by anything existing in nature or ever created by humans,
their capability to reproduce is far from self-explanatory. The genome or genetic
information, as an answer, is out of the question for obvious qualitative and quantita-
tive reasons (see later in Chapter 2, section “Is there any program in the genome?”).
Erecting animal structure requires more than the production of proteins, which are
the only products genes are known to account for. An animal organism is more com-
plex than a bag of proteins. Cells, not proteins, are the basic unit of life. Under no
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