Control Systems in the Living World - Building the Most Complex Structure on Earth - page 20

Parasympathetic
nerves

Sympathetic
nerves

ACh

ACh

Adrenal
medulla

Celiac
ganglion

EPI

Artery

Intrapancreatic
ganglion

ACh

ACh

A
cell

Glucagon

Pancreas

EPI
NE

Figure 1.12 Three autonomic inputs to the islet alpha cell. Preganglionic sympathetic nerves
travel in the spinal cord, releasing ACh from their terminals within the celiac ganglion. The
released ACh activates postganglionic sympathetic neuronal cell bodies whose fibers innervate
the islet alpha cells and release norepinephrine. Preganglionic parasympathetic nerves travel
in the vagus, releasing ACh from their terminals within intrapancreatic parasympathetic
ganglia. The released ACh activates postganglionic parasympathetic neuronal cell bodies,
whose fibers innervate the islet alpha cells and release ACh. Preganglionic sympathetic nerves
travel in the spinal cord, releasing ACh from their terminals within the adrenal medulla.
The released ACh activates the chromaffin cells to release the sympathetic neurohormone
epinephrine, which reaches the alpha cell via the arterial circulation. EPI, epinephrine; NE,
norepinephrine ( Taborsky, 2010 ).

and overcome the unavoidably increasing entropy of the system via feedback loops
that control the output and stabilize their structure. Hence, the control system is an
integral part of the living organism: “The existence and evolution of living beings
is impossible to be imagined without a system of control and regulation” ( Cabej,
1984 ). Even if by chance, or by human will and wisdom, a living structure arose
in the absence of a control system, it would immediately perish, as do most fish on
land. The emergence and evolution of control systems are inseparable from the emer-
gence and evolution of life. Control systems increased the freedom of the whole (the
organism) from the environment, at the expense of the freedom of the parts (organs,
tissues, and cells) whose activity was placed under tight control and regulation.
Theoretically, control systems in living organisms may be integrated or separate
for different parts of the living system. Integrated control systems are known to be