RE: “Odor Basics”, Understanding and Using Odor

[Guest guest]

Here's another one for the discussion (see below).

If I remember correctly, Herz claims MCS is fear based.

Is someone who has a peanut allergy told their efforts to avoid peanut exposure or their allergic reactions are "fear-based"?

When someone first develops MCS and puts 2+2 together, noticing that a lot of physical effects follow after an odiferous experience, there will be a period of adjustment where anything that smells will give rise to a pause that could be construed as fear based, but most people pass through that stage soon enough, realizing that not everything that smells causes a reaction.

Herz and the other guy who recently wrote a popular book about our olafactory senses have not studied the science about chemicals and toxins and poisons etc. And or get paid by the fragrance industry. And fail to take into consideration that many chemicals without a smell, cause the same toxic responses.

It is possible to perceive odours and not have any emotional or physical response to them. Just like it is possible to die from things that have no odour - radon, carbon monoxide..., or to be harmed by other poisons when one's sense of smell has been compromised (allergic rhinitis for example would contribute to that) And I'm told that it is not uncommon for people who have been poisoned by carbon monoxide to develop MCS. If it was a fear based response, they'd be walking around afraid of things that don't smell.

linda

(see article and release below... explaining one of the original purposes of having a nose)

Nose's alarm system found

http://www.thestar.com/sciencetech/article/309300

..."Scientists had thought such smells acted directly on nerve endings inthe nose, but the study in mice suggests special cells in the tip ofthe nose act as air quality control sensors that protect the body fromharmful chemicals...."This is one of these really hard-wired reflexes. It gives you time toget out," Restrepo said in a telephone interview....And they said it takes more than a mere whiff of an offending odor totrigger the response. Restrepo said only potentially dangerous levelsof odors can set off the protective gagging-and-coughing response...."There are some people who are especially sensitive to theseirritants."...

Irritating Smells Alert Special Cells, NIH-Funded Study Finds

http://www.nidcd.nih.gov/news/releases/08/03_04_08.htm

If you cook, you know. Chop an onion and you risk crying over your cutting board as a burning sensation overwhelms your eyes and nose. Scientists do not know why certain chemical odors, like onion, ammonia and paint thinner, are so highly irritating, but new research in mice has uncovered an unexpected role for specific nasal cavity cells. Researchers funded by the National Institute on Deafness and Other Communication Disorders (NIDCD), part of the National Institutes of Health, describe this work in the March issue of the Journal of Neurophysiology, now available online.

Weihong Lin, Ph.D., of the University of Colorado Denver School of Medicine and University of land, Baltimore County, led the study which discovered that a particular cell, abundant near the entry of many animal noses, plays a crucial and previously unknown role in transmitting irritating and potentially dangerous odors. Dr. Lin and colleagues from both universities plus the Mount Sinai School of Medicine identified the role of this solitary chemosensory cell in transmitting irritating chemical odors in the noses of mice.

Scientists have found similar solitary chemosensory cells in the nasal cavities, airways and gastrointestinal tracts of many mammals as well as fish, frogs and alligators; they think it is likely that they are also present in humans, explains Finger, Ph.D., one of the senior co-authors at the University of Colorado Denver.

Prior to this work, scientists who study smell and taste thought that irritating odors directly stimulated the trigeminal nerve, which senses touch, temperature and pain throughout the head region, including the delicate membranes that line the inside of the nose. The research team, under the guidance of Diego Restrepo, Ph.D., found that solitary chemosensory cells scattered in the epithelium inside the front of the nose respond to high levels of irritating odors and relay signals to trigeminal nerve fibers.

“This elegant research corrects an erroneous assumption about how irritating odors are perceived and expands our understanding of olfaction,” says F. Battey, M.D., Ph.D., director of NIDCD. “With further investigation, it also might lead to a better understanding of why some people are exceptionally sensitive to irritating odors.”

Solitary chemosensory cells on the surface of the nasal cavity are in close contact with trigeminal nerve fibers which end just below the surface. Earlier research revealed that these cells contain bitter taste receptors and that bitter substances applied to the surface of the nasal cavity trigger a trigeminal nerve response.

Intrigued, Drs. Restrepo and Finger decided to explore whether solitary chemosensory cells respond to irritating odors. Using nasal tissue from mice, the scientists measured a variety of changes in solitary chemosensory cells as they exposed the cells to low and high levels of several irritating, volatile chemical odors.

Among their observations were changes in electrical activity in the cells—which indicates a response to an outside stimulus—and changes in intracellular calcium ion concentration—which indicates signaling to other cells. Their measurements demonstrated that the solitary chemosensory cells responded to the odors and relayed sensory information to trigeminal nerve fibers.

Once stimulated, the trigeminal nerve will convey pain and burning sensations and can trigger protective reflexes such as gagging and coughing. The architecture of nasal tissue with solitary chemosensory cells on the surface and trigeminal nerve fibers just below allows the nose to detect a greater number of irritating odors, the scientists explain.

Fortunately, the threshold for triggering a response is high, so exposure to a small amount of an irritating chemical, as might naturally emanate from some kinds of fresh fruit, will not bring on gagging and coughing. For example, lemons contain the volatile chemicals citral and geraniol but at levels too low to trigger a trigeminal response. Only high, potentially dangerous levels of odors will trigger the protective gagging-and-coughing response.

The researchers point out that their findings provide an example of the Law of Specific Nerve Energies, conceived by Johannes Muller in 1826. Muller said that the way we perceive a stimulus depends on the nerve or sensory system that conveys it rather than the physical nature of the stimulus itself. In the case of irritating odors, we perceive them as irritating because they are transmitted via the trigeminal nerve, leading the brain to interpret the message as pain rather than as a smell.

The researchers say their findings raise new questions about how irritating odors are detected. They say more research is needed to explore whether solitary chemosensory cells are programmed to recognize specific irritants, which receptors are involved, and what steps a solitary chemosensory cell uses to convert a chemical stimulus to a signal it relays to the trigeminal nerve.

The NIDCD supports and conducts research and research training on the normal and disordered processes of hearing, balance, smell, taste, voice, speech and language and provides health information, based upon scientific discovery, to the public. For more information about NIDCD programs, see the Web site at www.nidcd.nih.gov.

NIH—the nation’s medical research agency—includes 27 institutes and centers and is a component of the U.S. Department of Health and Human Services. It is the primary federal agency for conducting and supporting basic, clinical and translational medical research, and it investigates the causes, treatments and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.

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