stimulate, or in some cases to inhibit, the post-synaptic neuron in the evocation of an action potential of its own. We use the term “tend” to call attention to the fact that a threshold level of stimulation may be required by the post-synaptic neuron; that is, the chemical stimulation may need to exceed some minimum level before the second neuron is caused to discharge. From a computer programming perspective, this is an extremely interesting aspect of the activation process because the stimulation can be cumulative across all the synapses connected to the post-synaptic neuron; if enough synapses are stimulated, the second neuron may be caused to discharge, even though the level of stimulation from any single synapse may not be sufficient to exceed the threshold. Again, from a computer programming viewpoint, this activity characterizes a decision making process; that is, it forms a gated switch. Consequently, not only can the information represented by the electrical discharge be propagated throughout a collection of neurons, but it can be propagated in an intelligent way because of the effects of many collections of neurons.

Paralleling the nervous system in most parts of the body is the endocrine system, which uses a similar communication channel to connect ductless glands with various cells of the body. When stimulated through their interconnections with the nervous system, these glands secrete distinct chemical molecules called hormones into the interstitial fluid surrounding cells relatively close to the glands, and from there into the blood stream where they are carried to specific receptor molecules found in various cells that may be far removed from the secreting gland. A hormone supplies a very similar function to a neurotransmitter, albeit within a different communication channel. In fact, a number of hormones are also neurotransmitters.

Within the endocrine system, each type of hormone effects what amounts to a logical communication channel through a physical fluid pathway. Each such pathway can carry different hormones and each hormone provides an information conveyance from the secreting gland to the receiving cells of that specific hormone. In a manner similar to synapses, the effect of a particular hormone may be reversed by a different hormone functioning in an antagonistic pair combination. When considering the secretion of hormones stimulated by control signals from the nervous system, the endocrine system appears as a distinct transport protocol layer (including a degenerative mode) if we view it in the guise of the communication reference model that we considered in Chapter 3. Through this layer, discrete sessions can be established to provide control of distributed cells over time via a feedback loop. We mention this point to illustrate the rather general interpretation that can be applied to interactions through a layered protocol model. We will make significant use of this approach in considering social systems in subsequent sections and chapters.

A particularly pertinent molecule for us to mention is one that functions both as a neurotransmitter as well as a hormone; the polypeptide, oxytocin. Known for its dual function in neural networks as well as within the endocrine system since the early XXth Century, the chemical structure and properties of oxytocin were studied and subsequently synthesized by Vincent du Vigneaud; work for which he was awarded the Nobel Prize in Chemistry in 1955. Functioning as a hormone, oxytocin is known to induce labor in pregnant women. Closer to our subject, more recent work suggests that functioning as a neurotransmitter, oxytocin is involved in the establishment and application of “trust” in human interactions. We present the term in quotes because it’s a bit unclear whether the use of the term in reported research exactly matches the definition we have adopted in this book. That slight ambiguity noted, it is most interesting to consider the report of experiments performed by Michael Kosfeld et al. in Nature in 2005 in an article entitled Oxytocin increases trust in humans. A subsequent article was published in the June, 2008 issue of Scientific American by Paul J. Zak, a member of the research team making the previous report in Nature.

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