What is scent composed of that allows us to be able to detect it? Also, how can receptors in our nose detect it and create an experience that we feel.
Side question: Is what we percieve from a smell different from the actual scent itself?
In: Biology
Scent is composed of chemicals. Merely molecules floating in the air, waiting to hit something. Just like the taste buds in your mouth are tuned to react to bitter things, acidic things, sugary things, and salty things and so-on by activating in their presence, so too do receptors in your nose. You inhale some of these free floating molecules and a few of them stick to the receptors in your nose. That sends a signal to your brain that that particular nerve (specialized like taste buds or the rods and cones in your eye to each detect different types of chemicals) to say “hey! This chemical is here! Activate this part of the brain and perceive it as a scent!”
To your latter question, that’s a bit unanswerable. A scent is a scent because it has been perceived as a scent. Otherwise, it is just a chemical in the air. If you pour bleach into a room with nobody in it, there is bleach in the air. The scent of bleach, then, is just your Air Chemical Makeup Detector (aka nose) sensing bleach (rather, chlorine) in the air and activating all of your bad scent nerves that set off the “acrid! Poison in the air!” Alarms. Similarly, a chocolate cake in a room will still fill the air with chemicals that your nose would detect as the scent of chocolate, but it isn’t a scent until your nose detects it! Until then, it’s just a molecule in the air like any other.
I suppose a tldr eli5 would be this: Scents are made by your nose detecting chemicals in the air, sending electric signals to your brain, and then discerning which nerves were activated to tell what that scent is. These molecules are always there whether someone is there to inhale them or not.
Your nose is like your tongue just “tasting” differently.
That fart you smell creating that “scent”. That’s your nose tasting the poop particles as they enter it.
Since we know that your nose is actually sensing actual particles of the thing you’re smelling, my household joke is that if we keep sniffing our tiny little dog, someday he’ll disappear.
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