by Dr. Mark Donohoe
Excerpted from 'Killing Us Softly'
OLFACTION AND IMMUNITY
The olfactory nerve, the first cranial nerve, is not a nerve at all. At least not in the usual sense of a nerve. It is, in my opinion, the strangest organ one could imagine. It is mysterious, primitive, courageous and an absurdity all at once.
In each other link between the inner world and the outer world, the messages are received through specialized receptors, converted to electrical impulses of varying frequencies, and the message is passed from neuron to neuron all the way to that part of the brain designed to interpret and respond to the message. Along the way, certainly, there are reflex arcs, collateral branches to eponymous nuclei, and a good deal of eavesdropping by other neurons. But the basic path is from external stimulus to internal perception - the outer world to the inner world.
The path is far from direct, however, and there is plenty of room for magnification, suppression, and misinterpretation along the way. The reason is that peripheral nerves, including the cranial nerves, converse only with the brain through synapses. These are the gaps between nerves, and the message changes from electrical to chemical transmission momentarily as this gap is crossed.
The chemical transmitters, known as neurotransmitters, include acetylcholine, serotonin, dopamine, histamine, and dozens of others. As the chemical is ejected from the axon of one nerve to the dendrite of another, the private message of the nerve becomes, as it were, more public.
Nearby nerves eavesdrop on the message, picking up a fragment here and there, and spread the gossip to nearby nerves. The nerves seem to then indulge in a crude form of democracy, collecting opinions to decide the fate of the message proffered from below. This indecipherable rabble of activity then organizes itself, contributes its opinion, sometimes strengthening, sometimes suppressing, sometimes re-routing the message.
More often than not, the message does not make it to the cortex, where the brain’s owner may become aware of it. It is lost along the way, extinguished entirely or passed on to parts of the brain responsible for these types of messages.
Even when the messages reach the cortex, the likelihood of perception is low unless the stimulus is novel, alarming, or at least a little unexpected.
The point is that all nerves face the ‘sensorship’ of synapses. All except one.
The olfactory nerve is less a nerve than it is a misplaced piece of the brain, dangling almost unprotected in the outside world. Like tubes of pork through a mincing machine, the brain cells spread through a finely fenestrated bony plate behind and slightly above the level of the eyes. Within deep clefts high in the roof of the nose, a square inch of deep yellow tissue on either side is home to around thirty million olfactory cells. Every last one of them, a card-carrying member of the central nervous system.
Even more astounding is the fact that these brain cells are “used up,” with a monthly cycle of regeneration of new cells to replace the old. Somehow, the “learned” response of those which degenerate is passed backwards to those which are to follow, preserving the learned olfactory responses and the receptor patterns.
It seems, to top it all off, that olfaction has an uncanny resemblance to another remarkable organ system - the immune system.
And the resemblance is more profound than mere analogy. Both immunity and olfaction are designed to detect molecules - those that belong to us, and those that most definitely do not.
The immune response manages admirably with large molecules, typically water soluble peptides, starches, nucleic acids and glycoproteins. These are typically swallowed, inhaled, or enter through breaches in our outer coverings. They become internal threats, and their presence is announced to the body through antigen presenting cells. These “consume” the foreign molecules, digest and splinter them , then sort through the debris to present just a few critical fragments on their surfaces. Not just any fragments, mind you. Only those sufficiently available and obvious, and those sufficiently different from our own molecules to ensure the future attack leaves healthy tissue of the host alone.
These often overlooked macrophages really are the brightest of the body’s cells, combining the skills of a computer, a librarian, and an entire judicial system in a single cell. Many may say (and I am not one of them, mind you) that this last added quality adds nothing to the total of its wonders.
A novel virus appears, say, on the nasopharynx, along with many of its friends. This is surely a splendid place to take up residence, they think among themselves. All facilities laid on - moisture, darkness, sugars, mucus - heaven on a stick in virus terms. Before long, however, in the normal course of business, a scene reminiscent of a third rate 1960s Japanese movie emerges. A monstrous, formless blob, the size of a whole building, flows into an outstretched tentacle of its own making, and consumes dozens of the viruses sitting smugly in the soggy warmth of their newfound home.
Within minutes, the verdict is in. “Guilty - Not welcome”, and the message along with a molecular snapshot of the offender is hoisted on wanted notices all over the surface of the macrophage.
The jig is up. The vacation for the intruder is about to come to an end, and the story is finished apart from the mopping up operation. Within minutes this is carried out by lymphocytes blaring their own chemical sirens. These sidle up alongside the macrophage, take a photocopy of the offender’s image, and then clone themselves, each with an image of the intruder in mind. The virus has little chance at this point, and must surely consider the whole deal a little like a seaside holiday in a hurricane. The only escape is into the cells surrounding them, where the whole process starts again.
The olfactory receptors, on the other hand, are well designed to detect smaller molecules, almost exclusively fat soluble.
The greasy surface of the receptor area is almost impervious to water soluble molecules, and the design of the roof of the nose is such that proteins and dust are rarely encountered. They are just too heavy, too sticky and too big for this. They become trapped in the mucous and hairs of the nasal cavity, and are most often swept back out in that act of almost orgasmic delight and relief, the sneeze.
Each of us has around three hundred or so distinct odors, and the unique combination goes to make up our own “smell signature.” Just as with the immune system, which learns the “immune signature” of its owner in the thymus gland in infancy, we are “blind” to our own signatures most of the time. Were it not so, we would be attacking our own tissue unmercifully (as is the case in autoimmune disease), or drown in our own redolent aromas, losing all possibility of distinguishing the faint scents upon which we depend.
The structure of our noses is less amenable to showering of the receptors than it is for many of our mammalian relatives. Sheep dogs and Alsatians not only have around forty times more olfactory receptors, they have an air pathway through the nose which guarantees molecular intermingling with the deep reddish-brown mucosal surfaces. We humans need to flare our nostrils, squint our noses, and draw breath in a most unusual fashion to really get those aromatic molecules into the folds of our upper noses.
We usually need to “sniff” to really get a grip on these ephemeral messengers. A single molecule is sufficient to cause a response in a single nerve, but this will still be lost in the noise of the other, more abundant molecules trapped in the sniff. We seem to need about forty or so nerves firing before the cascade of magnification in the “smell brain” occurs.
One can imagine that the increase in “olfactory noise” which has occurred as a result of our chemicalized century would be making this process more difficult and tenuous all the time. It is my own opinion that we really do smell less these days than when I was a child, and there is some evidence for this. That, however, is a different story.
What happens between reception and recognition is something of a divine mystery, one we are only beginning to unravel using tools from chaos theory, functional brain imaging, and animal studies.
There is no easy way to understand what occurs in the olfactory bulb, and how that message is disseminated for use from that point.
Those familiar with the concept of chaos and “attractors” have a better chance than most, but it is still a wonderfully mysterious process, deserving of our urgent attention.
As the molecules in question bind to the nerves with the matching molecular “receptors,” the nerve not only gives an electrical “quiver,” it seems that the molecule itself is transported into the cell itself, in an event reminiscent of the poor viruses and the macrophage.
Why would we want these molecules inside our cells? More specifically, why would we want them in our brain? In medicine, we learned of a mythical creature known as the “blood-brain barrier,” the purpose of which was to prevent foreign molecules from entering the territory of thought and consciousness. So why would there be such a shoddy back door to such an elaborate system of protection?
To understand the purpose, we may need to understand the brain.
WHAT IS A BRAIN?
The answer seems obvious. It is a thinking machine, an exquisite and infinitely complex computer. Some may even say that the brain is the seat of consciousness, the thing that makes us who we are.
Closer inspection is less than supportive of this cerebro-centric view of the human brain. In fact, when you really get down to the basics, this view seems more and more like the view of the ancients, that the earth is the center of the universe, and all revolves around it.
The brain is a gland. Or rather, it is a part of a glandular complex called the endocrine system.
Most of the brain conducts boring, slow hormonal business, gaining input from its distant receptors throughout the body, and sending molecules forth to ensure that the internal environment remains a fit place to live. This miracle, known as homeostasis, allows past sea dwellers to live in the dry and inhospitable atmosphere.
We carry our private seas within, and our hormones are bottled messages, adrift on the waves and tides which bathe our every cell. They drift in their billions. Some, like thyroid stimulating hormone, usually carry fairly simple messages; “Doing fine, maintain course”; “Temperature dropping, step it up a little”; and the like.
Some, such as adrenaline, fire off more complex and urgent missives, such as “Predator chasing - breathe faster, open airways, open vascular floodgates to muscles, pump stronger, cease digestion, and run for your life.”
They are certainly amazing molecules, hormones. They are the language within, the phonemes, utterances and gossip of the body. Each has its own factory and chain of command, each has a shape which seems to actively seek out receptors on the cells designed to receive its message, each has specific and powerful effects at astonishingly low concentrations, and each participates in a most extraordinary and exquisite feedback system.
The hormones have ghosts, you see. The molecule is made in the gland, the receptor is made in the cells which listen for, even yearn for the message. One would think that that was that. Message sent. Message received. Over and out.
The truth is far from that. Firstly, hormones need a feedback mechanism, a way of asking for more and communicating their satisfaction. This is where the brain comes in handy. It is a good organizer and is able to sort through conflicting and complex messages as if designed for the task. The foot hits the appropriate accelerator or brake, and the stimulus is reset.
There are a couple of levels to this. Usually, the organs which produce hormones - the pancreas, gonads, adrenals, thyroid and many more - are dotted around the body for no particularly good reason. Far flung outposts, they seem on the end of a tenuous and indirect communications system.
When compared to the nervous system, these remind me of smoke signals compared to telephones. It may be the reason that doctors have long overlooked the importance of the endocrine system – it is too old, indirect and messy to have too much relevance for “modern man.”....
What is the value of such an indirect system? It seems that the answer lies in the almost effortless ability of the system to sort itself out, to manage the amazingly complex task of running all the trillions of cells in the body, all without a pilot. That is it. The endocrine system is our body’s autopilot, good enough to manage most day to day tasks which would otherwise require our entire focus and attention. The brain invests in an automated solution. We are on autopilot, yet like a kid in the cockpit, we are given a wheel to let us pretend that we are driving. Then, like the child, we turn the wheel whichever way the jet goes, feigning control.
…So what happens when the “olfactory noise” increases? Hundreds of thousands of new molecules, all with no evolutionary history and no appropriate response, bombard the olfactory epithelia and the vomeronasal organ with every breath. What happens? It is hard to say, as truly novel molecules were a rather rare occurrence until this century. Nature usually edited old and successful molecules, and recycled the general structure of the important ones….
If one had to guess, it is likely that the “default” response to a new molecule would be to interpret it as bad news, a threat or a poison.…The biologically successful response [to chemicals] would be one which could identify and minimize such exposure. One which could induce a sufficiently strong aversion response to prevent ongoing risk and damage. MCS.
….MCS may, in short, be an adaptation to a lousy environment by developing the skills to avoid such environmental exposure. Those with MCS may, in fact, be the most normal people in the world. One could even suggest they are advanced compared to the rest of us, with a heightened sense able to detect and minimize risk for survival.
About the Author: Dr. Mark Donohoe is an Australian GP specialized in Environmental Medicine, with a special interest in ME/CFS and chemical sensitivities, adverse effects of medications, and vaccination issues.
This article is excerpted from a book on multiple chemical sensitivities – Killing Us Softly - that Dr. Donohoe offers online for free download and sharing. He asks only that those who wish to share the book do so by passing on the link to his download page (http://web.mac.com/doctormark/DoctorMark/KUS.html )