Rise of the Animal Kingdom and Epigenetic Mechanisms of Evolution - Building the Most Complex Structure on Earth - page 260

the controller of the ICS, sequentially down through the lower levels of organization
ending at the molecular level of gene expression.
The animal control system consists of the following:
● The sensory division of the peripheral nervous system (PNS), a dense and pervasive pres-
ence of sensory receptors, which are located at the surface of the body to receive exter-
nal stimuli (exteroceptors), sensory receptors that receive stimuli arising within the body
(interoceptors), and those that are located primarily in muscles, tendons, and joints and
receive information on the length and stretch of these parts (proprioceptors). All types of
receptors send their information to the CNS where they are perceived.
● The incoming information is processed in the CNS, the controller of the ICS, which moni-
tors the state of the system and continually provides its output in the form of signal cascades.
The integration and processing of the interoceptive input on the state of the sys-
tem, as well as decision-making for restoring the normal state, are functions of the
controller of the ICS, which is the CNS (see Figure 1.12). By comparing the informa-
tion on the actual state with the “normal” state, the CNS identifies deviations from the
norm and sends instructions for activating signal cascades to restore the normal state.
Being hierarchical, the ICS model is an epigenetic top-down model where con-
trols at all levels are coordinated. In this hierarchy, the lower levels of control are
subordinate to, although they interact with each other, the control of the higher levels.
The genome is also subordinate to rules of the whole, that is, of the cell, the organ-
ism, and the ICS, not the other way around. The neoDarwinian bottom-up model pos-
iting that the genome controls the functions and the structure of animals contradicts
the experimental evidence to date and, in doing so, puts the cart before the horse.
The epigenetic top-down model is supported by two fundamental biological
phenomena:
1. Expression of housekeeping genes in animals is regulated by epigenetic signals from the
cytoskeleton (see page 128-131).
2. Expression of systemic (nonhousekeeping) genes is controlled and regulated by extracel-
lular signals, which ultimately originate in the ICS (nervous system).
Cell differentiation is generally considered an epigenetic process ( Maruyama et al.,
2011; Reik, 2007 ) and serves as a major and universal illustration of the top-down flow
of information in the process of development. All cell types in an organism have the same
genotype or DNA, but differ from each other due to the different epigenetic information
(extracellular signals) they are given through signal cascades starting in the CNS.
Is it possible that the CNS might control events at a cellular level?
This question may be less troubling than it seems when we bear in mind that our
brain contains up to 1 trillion neurons, each connected to thousands of others, which
makes the brain capable of executing as many as 100 billion operations per second.
But a glance at the general scheme ( Figure 5.4 ) of neuroendocrine regulation is
our best empirical answer; the brain, via the pituitary, neurohormonally controls and
regulates the expression of specific genes in a dozen distant organs.
The epigenetic mechanisms of the cell are not reflected in this figure.
In mammal cells, the cytoskeleton is in contact with both the extracellular
matrix (ECM) and the nuclear matrix, acting as a transducer of extracellular signals
to the cell nucleus. Intermediary filaments (IFs) are intimately connected with the