Saturday, August 16, 2008

Brain as Composter II

In reference to Brain as Composter:

Here are the four "pairs" of eight principles of design mentioned by Dan Hemenway in his article over two decades ago. They were likely noodled around somewhat in order to present well, and in alignment with 'ancient philosophy' on harmoniousness, and so they do.

On economy: "
1. Do only what is necessary. This involves humility in realizing that our understanding is limited. It means a respect for the natural way in which things happen.
This is what the radical farmer Fukuoka means when he says that his is a "do-nothing" philosophy and why he always questions the reason for every task. "If it ain't broke, don't fix it."
Conservation is always the first resource of "doing nothing." In its simplest terms, it is putting on a sweater instead of turning up the thermostat. As a state of mind, that's a fair beginning. In the deeper application, conservation means honoring the naural cycles, not breaking them apart which results in "waste."
Conservation involves passive restraint from change or disruption of natural systems and active participation within them."

I remember the basic organizing principle as written by Angevine in Encyclopedia of the Human Brain (here's a link), centralization, third one in:

"3. Centralization

The key feature of the nervous system is centralization. It offers few circuits for local interactions of body parts. The CNS is almost always involved even if the distance, as from thumb to index finger, is slight. Intercession of the brain and spinal cord ensures integrated and coordinated activity.

Exceptions are instructive. The local cutaneous response to irritating stimuli (raking a blunt probe over the skin) has three components: local reddening (vasodilation from injury), wheal formation (transient edema from tissue fluid extrusion), and ensuing vasodilation (flare) with lowered thresholds and increased sensitivity to pain (pinprick). The flare and hyperalgesia represent an axon reflex. Nociceptive (pain) nerve endings are activated by substances released by injured tissue cells, and nerve impulses are conducted a short way centrally along nociceptive axons and then distally over branches of these axons to nearby arterioles, causing them to dilate. Advanced or primitive (it is sluggish, starting in about 20 sec. and developing fully in around 3 min), this reflex involves local nerve fibers only, not the CNS.

The "triple response" illustrates three concepts. Pain receptors sense chemical, as well as mechanical and thermal stimuli. Their sensitivity is increased by substances accumulating in the damaged area. Their response includes a neuroeffector component. They release substances (peptides) that initiate further events, providing further protection and favoring local tissue repair.

Studies in invertebrate neural systems show extensive local control of visceral function. Exceptions to central control are also found in the mammalian ANS. Near-normal interaction of bowel segments persists in the absence of CNS innervation. Sensory fibers from the gut exert feedback in intramural autonomic ganglia on visceral motor neurons regulating smooth muscle in the intestinal wall. The nervous system has pattern generators, both central and peripheral: systems with cellular, synaptic, and network properties (cyclic firing rhythms, reciprocal inhibition of cell pairs, leader and follower cells) that provide automated mechanisms for generating rhythmic movements (breathing, walking) or periodic activities (sleeping, waking). Regulated by neural (sensory feedback, volitional override) or neuroendocrine influences, pattern generators are pithy examples of neural endogenous activity." Do more with less would seem to be the message here."

Back to Hemenway, on elegance:
"2. Multiply purposes. Never do anything for only one reason. "Stack functions" is the way Bill Mollison expresses it.
In nature, all design is elegant. My hand is clearly designed for grasping. But it also serves as a heat radiator for my body, a weapon (fist), a signal device, a bodily support surface (as in pushups), a sensory organ, a carrier of affection (caresses), and an implement of communication (fingers in sand).
If we perceive several functions of an object of decision, then many more will be present. If we perceive only one function, then fear, greed, or our egos are in the way."

This property reminds me of Angevine's 8th principle, chemical message coding:
"8. Chemical Message Coding

The basic function of the nervous system, from which all others derive, is communication, performed (with unsung neuroglial support) by neurons. It depends on special electrical, structural,and chemical properties of these diversified cells with their long processes, on their exploitation and refinement of two basic protoplasmic properties, irritability and conductivity, on their external and internal neuronal morphology featuring multipolar shape and integrative design, almost infinite modes of dendritic and axonal branching, widespread, diversified connections, and specialized organelles, and on their use of chemical substances to encode, deliver and decipher messages of their own and other neurons.

Neural circuits are chemically coded. Neuroanatomy encompasses interneuronal connections and also chemical mediators and transmitters. Neuroactive substances comprise neurotransmitters, neuromodulators, and neurohormones. Their definition in contexts other than site of action, postsynaptic neuronal activity, and corelease of one or more additional neuroactive substances can be misleading. Neurotransmitters are small molecules acting swiftly, locally, and briefly on target cells. Neuromodulators are very small (peptides), regulating but not effecting transmission, and neurohormones are also small, with intrinsic activity mediated by neuronal and other cells, exerting slow, widespread, and enduring influence via the extracellular fluid or bloodstream.

Neurons releasing hormones are quasi-endocrine cells, liberating secretory products from axonal endings into the perivascular space to be conveyed to blood vessels and thence to target organs. The provincial concerns of neurophysiology and endocrinology have fused into neuroendocrinology, as psychoneuroimmunology has united psychobiology, molecular neurobiology, and immunology."

More to come.

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