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Main olfactory bulb
The main olfactory bulb has a multi-layered cellular architecture. In order from surface to the center the layers are
• Glomerular layer
• External plexiform layer
• Mitral cell layer
• Internal plexiform layer
• Granule cell layer
The olfactory bulb transmits smell information from the nose to the brain, and is thus necessary for a proper sense of smell. As a neural circuit, the glomerular layer receives direct input from olfactory nerves, made up of the axons from approximately ten million olfactory receptor neurons in the olfactory mucosa, a region of the nasal cavity. The ends of the axons cluster in spherical structures known as glomeruli such that each glomerulus receives input primarily from olfactory receptor neurons that express the same olfactory receptor. Glomeruli are also permeated by dendrites from neurons called mitral cells, which in turn output to the olfactory cortex. Numerous interneuron types exist in the olfactory bulb including periglomerular cells which synapse within and between glomeruli, and granule cells which synapse with mitral cells.
As a neural circuit, the olfactory bulb has one source of sensory input (axons from olfactory receptor neurons of the olfactory epithelium), and one output (mitral cell axons). As a result, it is generally assumed that it functions as a filter, as opposed to an associative circuit that has many inputs and many outputs. However, the olfactory bulb also receives "top-down" information from such brain areas as the amygdala, neocortex, hippocampus, locus coeruleus, and substantia nigra. With this in mind, its potential functions can be placed into four non-exclusive categories:
• discriminating among odors
• enhancing sensitivity of odor detection
• filtering out many background odors to enhance the transmission of a few select odors
• permitting higher brain areas involved in arousal and attention to modify the detection or the discrimination of odors
While all of these functions could theoretically arise from the olfactory bulb's circuit layout, it is unclear which, if any, of these functions are performed exclusively by the olfactory bulb. By analogy to similar parts of the brain such as the retina, many researchers have focused on how the olfactory bulb filters incoming information from receptor neurons in space, or how it filters incoming information in time. At the core of these proposed filters are the two classes of interneurons; the periglomerular cells, and the granule cells.
The basal dendrites of mitral cells are connected to interneurons known as granule cells, which by some theories produce lateral inhibition between mitral cells. It is not clear what the functional role of lateral inhibition would be, though it may be involved in boosting the signal-to-noise ratio of odor signals by silencing the basal firing rate of surrounding non-activated neurons. The synapse between mitral and granule cells is of a rare class of synapses that are "dendro-dendritic" which means that both sides of the synapse are dendrites that release neurotransmitter. In this specific case, mitral cells release the excitatory neurotransmitter glutamate, and granule cells release the inhibitory neurotransmitter Gamma-aminobutyric acid (GABA). As a result of its bi-directionality, the dendro-dendritic synapse can cause mitral cells to inhibit themselves (auto-inhibition), as well as neighboring mitral cells (lateral inhibition).
Olfaction is distinct from the other sensory systems where peripheral sensory receptors have a relay in the diencephalon. Therefore the olfactory bulb plays this role for the olfactory system.
Research has shown that body odor is connected to human sexual attraction.[1][2] Both fluctuating asymmetry (FA)[3] and the human leukocyte antigen (HLA)[4] are connected to scent. HLA is the human version of the major histocompatibility complex (MHC), a protein complex that plays a role in an individual’s immunities and self- versus nonself-recognition.[5] FA affects body symmetry, which in turn affects body size and stress tolerance.[3] Studies have not suggested that one scent caused by a particular HLA is more attractive to all individuals, but they have demonstrated attraction between individuals of certain HLA types.[6] Research has also shown that the scent of low FA person is universally more attractive,[3] and that facial attractiveness is connected to attractiveness of scent.[7]
I think I stated that why there are a lot of scents available, there were two that have stood out as being used by a large majority.
Originally posted by Domo1
K dude explain why there are so many choices in the deodorant aisle. Name the brands. What about cologne? Is this a chav thing? I dont ever recall being able.to smell girls deodorant. I know alot of low.class guys use axe.spray... but that is relatively new. Old spice.is the only thing I remember a slight majority wearing.
Great thread! Smell is powerful and I find this interesting. Well done.
Originally posted by ThisIsMyName
Interesting piece you have composed.
I have stopped wearing deodorant and cologne for the past couple months for many of the reasons you write within your article, however I never thought about the psychological effects.
My friend made a comment that was very interesting when some girl smeared him for not wearing deodorant, he said "What smells better, some toxic artificial smell or natural hormones?" This brings an interesting thought about human hormones and how they are effected and even suppressed by deodorant and cologne.
It is very true that these markets have hijacked out senses, not just our noses.
No it didn’t, you were just wanting clarification which I completely understand.
Originally posted by Domo1
reply to post by IgnorantSpecies
Man that post I made sounded really bitchy. Sorry. Unilever huh? This is actually one of the most interesting theories Ive read on this site.
Yeah I have heard about this, but that would probably take high quality ingredients.
ETA question. I know with the higher priced colognes body chemistry alters the smell which is why your supposed to spray on skin instead of clothing. That right? I suppose I should google it.
Originally posted by minor007
It is a myth that we need deodorants to pull the opposite sex. When we sweat our bodies will have an distinct odour. This odour will either smell sweet to the opposite sex or it will be repulsive. This smell does not cause arousal for the opposite sex however it be a pleasant smell when you have sex with them. Theres no need for deodorants unless you only bath/shower once a month
4. Potential for odor to cause stress - "The perception of odor is dominated by the pleasantness-unpleasantness dimension," Schiffman reported. "Pleasant aromas such as cookies baking in the oven beckon us, whereas, unpleasant odors such as those from a garbage dump repel us."
7. Chronic exposure to odors - Several studies show people adapt to odors, especially in the workplace. Tests show these workers are not as sensitive to the odors as unexposed people. "Long-term adaptation to animal odors occurs in persons who work daily in highly odorous environments," Schiffman reported. "It accounts for the finding that persons who work with livestock cannot fully understand the complaints from neighbors who only receive odors intermittently."
5. The role of conditioning in odor responses - "Conditioning or learned associations can play a role in symptoms induced by odors," Schiffman said. One research project showed panic and hyperventilation symptoms were learned after an acute exposure to chemicals. Before the exposure, the chemical odors were tolerated.
Propylene glycol is neurotoxin known to cause contact dermatitis, kidney damage, and liver damage. In the Material Safety Data Sheet (MSDS) for propylene glycol, the National Institute for Occupational Health and Safety warns workers to avoid skin contact with the toxic chemical, and yet millions of people apply it under their arms everyday. From the MSDS: "May cause eye irritation, skin irritation. Chronic exposure can cause gastro-intestinal disturbances, nausea, headache, vomiting, and central nervous depression."
Inhalation: No adverse health effects via inhalation.
Ingestion: Relatively non-toxic. Ingestion of sizable amount (over 100ml) may cause some gastrointestinal upset and temporary central nervous system depression. Effects appear more severe in individuals with kidney problems.
Skin Contact: Mild irritant and defatting agent, especially on prolonged contact.
Eye Contact: May cause transitory stinging and tearing.
Chronic Exposure: Lactic acidosis, stupor and seizures have been reported following chronic ingestion. (Relatively normal for any substance someone is chronically exposed to)
Originally posted by Domo1
reply to post by IgnorantSpecies
I findit odd that Ive never really heard of Unilever. I know of Monsanto (frankly I enjoy taking their side for some of the cokments I get here) and find the monopoly and business practices they employ beyond creepy. This really is a very interesting thread. I wish I had the laptop with me so I could research a bit more. The axe thing always really weirded me out.
Originally posted by IgnorantSpecies
reply to post by ArrowsNV
Well as far as I can tell there is enough reason for these chemicals to have much more extensive and long term testing then they have had done, certainly enough reason to be concerned about them.
I don't want to sound too out there but we aren't always told the full truth about these things, especially when a corporation is making billions of dollars off them.
Your 2 cents is appreciated, but it is a rather small part of the thread.
I would be interested to also hear your opinion on other parts of the thread if you have the time.
Thanks, hope I didn't sound rude its just that the Monsanto issue really scares me.
Originally posted by Domo1
reply to post by IgnorantSpecies
Advice taken Ill get my chuckles elsewhere. The axe thing weirds me out because it was such an overnight thing. I remember it came out, all of a sudden everyone under 20 was using it. Too much of it. Locker room waas like a damn fog with that stuff. The part I found strange was that every girl I knew hated the smell, but guys bought it to impress them. Jeez maybe axe is oopulation control.
Well the problem with chemicals like this is you probably wouldn’t notice any ill affect, seems like something where the problems manifest over a long time or induce other problems.
Well I agree with all the other analyses of the other chemicals mentioned for the most part. But having used PG for well over 4 years with no ill affect, and not just putting it on my skin, I firmly believe that it is a very non toxic chemical in the doses used for deodorant and other products such as my electronic cigarette. Although it (PG), like any other chemical out there, CAN be toxic, it is all dose dependent. For example; I've been more worried about the nicotine in my e-cig fluid than the Propylene Glycol and for good reason. Whereas the LD50 of PG (in rats at least) is 20g/kg (guesstimating here, but about 1,160g would be needed to kill a human) it only takes about 46mg of Nicotine to kill a non smoking adult (about 1.2mg/kg). I could go on, but I'm rambling. Long story short, it's a safe chemical that a lot of people confuse with its cousin; anti-freeze (EG, ethylene glycol). As for the body of the "conspiracy" I do not doubt it in the slightest. As was said, smell is one of, if not, the greatest and most powerful senses we as humans possess, and I can clearly see where it would come into play as suggested in the thread. Like I stated in my last post, that little bit was my only concern, but after re-reading the article and the rest of the thread I do agree with what has been posted. (With that tiny exception on PG)