How does smell work? The Weird Quantum Connection

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How Does our Olfactory system work? How do we Smell? It turns out that quantum mechanics plays a big role. What you may not realize is that inside your nose rests a very sensitive quantum device that uses complex physics to give you the ability to distinguish, according to the latest estimates, 1 trillion different smells.
In order for you to smell anything, molecules from that thing have to make it to your nose. Everything you smell is volatile is some way, meaning it is giving off molecules that float into the air and land inside your nose.

But how do these molecules trigger the sense of smell? At the top of your nasal passages behind your nose, there is a patch of special neurons about the size of a postage stamp called the olfactory epithelium. They have hair-like projections called cilia that increase their surface area. Any molecule from anything with a smell binds to special smell receptors on these cilia and triggers the neuron causing a signal to your brain. This signal ends up in a primitive part of the brain called the limbic system which is associated with emotions and memory – so that is why smells can trigger strong memories and emotional reactions.

These neurons are unique they come directly from your brain, and are out in the open where they can come into contact with the air. So this is the only place on your body where your central nervous system is directly exposed to the environment.

Now the questions is how do the neurons get triggered? The standard explanation going back to the 1950’s had been that the receptors at the ends of these olfactory neurons can only accept particular shapes of molecules. There are 400 such smell receptors. And the exact type of smell is determined by how the molecules from the smelly compounds fit in the set of receptors of the receiving olfactory neurons. By triggering a particular combination of the 400 smell receptors, the brain interprets a particular kind of smell. It’s like a lock and key. The key is the shape of molecules of the smelly compounds. And the lock is the olfactory receptors. One combination can trigger the smell of a rose, another combination can trigger the smell of rotten eggs and so on.

This was the standard explanation for the mechanism of smell, until researchers discovered that you can have molecules of different shapes that have the same smell. So for example cyanide smells the same as benzaldehyde, a bitter almond smell. But they are vastly different shapes. So scientists concluded that there must be something more than just the shapes that determines smell. Well it turns out that although their shapes are different, cyanide and benzaldehyde have the same vibration. And new research suggests that it is not just the shapes of the molecules, but also the vibrations of these molecules that determines how we perceive the smell.

All molecules vibrate with a certain frequency, and tempo, based on their structure, bonds and weight. Its analogous to sounds coming from various instruments due the their various shapes. Luca Turin, a biophysicist at the Alexander Fleming research center in Greece conducted experiments using the the smell of sulfur compounds. What he found was that these compounds with the same vibrational frequency of sulfur do indeed smell like sulfur, even though their molecules are shaped completely differently.

In quantum mechanics, so-called particles like electrons are really waves of probabilities until the moment they are measured. The probability wave is such that when the particle encounters a barrier, the probability wave does not stop at the barrier, but continues through for a short distance. So there is non-zero probability that the electron will go straight through the barrier and show up on the other side of a barrier, or tunnel through this barrier. This is called quantum tunneling.

It is theorized that the vibrations of certain molecules might allow electrons from the receptors to tunnel through to other receptors, and trigger signals in the neurons, and to the brain. Different molecules with different vibrations can cause different rates of tunneling. When the molecule of the odor has a certain frequency that matches the energy of the receptor, it opens a gateway for an electron to tunnel more preferentially than when the molecule is not present.

In a way, you might say our noses not only smell shapes, but hear shapes too using the complex physics of quantum mechanics to do it. How could our noses have evolved such a sophisticated sensory mechanism? Turin has an interesting answer, he says “Four billion years of R&D with unlimited funding is a long time” – indeed evolution is a process we have probably greatly underestimated.

#olfactory #senseofsmell
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Quantum biology...a new frontier. Ain't science grand?

FobbitMike
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I am in my mid 70's, in the last 10 years or so I detect strong smells that no one else can. Usually loosely described as chemical odours. When I awake they are very strong but strangely they create false memories, as if they go with times of my life, but not as I am now. As a parallel life where things play out differently but still me. I lay without moving, trying to make out what the smells are that are so familiar to me. When the smell gets too strong I feel like I am in a nightmare and I know that sooner I raise myself from lying position, the smell will go away.

sharon
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Smell plays an important role in social interaction. For example, the perfume industry is a multi-billion dollar business which produces and sells products whose purpose is to change the way that people smell. In my opinion, this shows how much humans are affected by smells; we even go so far as to spend a large amount of money on them!

compellingpoint
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Thank you thank you thank you for this video. This video isn't as popular as many of your other ones, but sometimes they're just as needed to some even if the demand isnt always so high. Thankyou for your dedication and for the effort you and anyone else involved in your channel put into this one and all your others.

jessicamaccabe
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Wow I'm taking a class on a related subjected and I really got sucked into this video. He articulates well enough to explain such a complex issue so simplistically you can understand.

deniseedwards
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so cool! it explain how they're so different 😮👏 thanks for your video! 🎉

mikibellomillo
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Very educational. Cleared out all my doubts 👍🏻👍🏻👍🏻

veyrondarren
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As usual very interesting and well presented! Thank you.

redpower
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So once I came across a bag with something nasty inside of it, I had to pick it up and discard it but the odor that came from it was absolutely Earth shattering. I'd never smelled something so bad. But as I smelled it, a vivid memory triggered. But a memory of an experience I don't remember.

Actually I wasn't even a part of the memory, it was more an observation of a couple of things, and the feeling, or the atmosphere of the images. It was a really strong experience. Almost like a vivid dream. I could see vividly and feel strongly. But I have no idea what it was, it was very cryptic. For days afterwards I would think of that smell and the exact same memory would come back. Now I can't remember the smell, but I remember what I saw, and I remember the description I gave of the feeling I had. So weird, I just wonder what it could have possibly been. A hallucination? But could an odor trigger a hallucination, and I wasn't seeing things, I was remembering things.

It was like the smell gave me a peek into something, and I could feel what the general motive, energy or intention behind what I was looking at was. Weird, I just can't explain it.

ptimal
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Smell is so fascinating. Who would have thought 50 years ago that the human body uses quantum mechanics. Simply amazing. Everytime we discover something fascinating and new we find out nature beat us to the punch.

gearhead
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Another fascinating presentation - thanks. For yeas since school I'd gone with your first explanation but the newer research does seem strike a chord. I was trying to calculate how combinations of 400 sensors could possibly cover all the millions of smells, but went with the quantum explanation instead ;)..

watchfordpilot
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Love your haircut.... and your content of course.

jasper
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So, you're telling us we don't even have to be on acid to smell shapes?

meischel
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I don't get how this channel has so few views with such great and consistent content.

SkyClap
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Hi Arvin -
I recently subscribed to your channel and started watching your amazing videos. In this video, at the end, you mentioned that we can "hear shapes too" using the complex physics of quantum mechanics. Is it really true? Is there a real research on this? If yes, please provide a note or video if possible.

sitaramayyagari
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Cheers arv I'm only 15 and hate science but your videos are so so soo fascinating

willmee
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If somebody who’s already guessed this was due to Quantum Tunneling then they’ve developed some kind of intuition for Quantun Mech and that’s a good thing! Good presentation

dean
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I always carry a noseclip for when I get in an elevator, someone always drops a SBD (* SBD = Silent But Deadly, a very smelly noiseless fart ) -- my girlfriend always used to fart in then laugh

mickkennedy
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6:13 Man Arvin is on some other universe bro

Shaaan
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“Vibrations determine smell”
String Theory has entered the chat

nacht