created by Tf2ToxicSoldierMain on 14/03/2025 at 23:18 UTC
82 upvotes, 4 top-level comments (showing 4)
Comment by DougPiranha42 at 15/03/2025 at 19:56 UTC
94 upvotes, 2 direct replies
For every different scent you can pick up, there is a dedicated small part of the brain (in the olfactory bulb) that sends nerves to the lining of the nose, which nerves have a unique receptor for that scent molecule. https://en.m.wikipedia.org/wiki/Olfactory_receptor[1]. Humans have a few hundred of these, dogs have tens of thousands. As the sense of smell is processed in the brain, the brain can detect further things: combinations of multiple scents, or changes in the intensity.
1: https://en.m.wikipedia.org/wiki/Olfactory_receptor
Comment by ReasonablyConfused at 16/03/2025 at 04:37 UTC
25 upvotes, 1 direct replies
I just want to add that a full understanding of smell is something we don’t have yet. Just 25 years ago, we were theorizing that there were receptors for each smell. This would mean thousands of different receptors to smell the world around us.
Turns out most smell receptors have varying degrees of affinity for many different types of smells. The brain then processes the signals sent to it from multiple different receptors. A surprisingly large percentage of the human genome is dedicated to smell. It’s important.
One of the surprising features of human smell is our sensitivity to petrichor, or “rain/wet earth.” Humans use a lot of water and will need to find it when we travel long distances. Out sensitivity to this smell far surpasses the sensitivity sharks have for blood, so even though our noses are small, we have one of the most sensitive noses in the animal kingdom, but just for that one smell.
Comment by Mitologist at 16/03/2025 at 03:28 UTC
4 upvotes, 0 direct replies
Smell receptors are activated by different specific patterns or groups on target molecules, and project to specific regions of the brain. Every molecule can thus activate several different receptor types to varying degrees. The brain recognizes, learns and interprets the pattern of activation a molecule causes. Therefore, even though we have many different smell receptors, we can differentiate many more substances than we have receptor types. Dogs and humans differ in that dogs have more receptor cells, not necessarily more types, so they are more sensitive. Smells differ with concentration , because at low concentration, the weakest receptor answers may not be there, whereas at high concentrations, some receptors may be overloaded. Both changes the pattern of relative intensity between receptor types that the brain interprets, leading to different sensations. Perception of smell is really fascinating, especially the hardwired analysis and information processing.
Comment by ResearchersMarina at 16/03/2025 at 16:59 UTC
1 upvotes, 1 direct replies
each receptor for each scent is a theory generally used, but there are million of molecules with distinct scent and we need million receptor. I will be more inclined to think that different structure binding to one receptor producing different signal level in olfactory nerves will be more appropriate. It will explain why all alcohol has similar smell with slight variation.