Odour

[Ashish]

whats responsible for the odour for any material or substance or which property is responsible

[hermanntrude]

smell is a very complex sense. It works as a cross-reactive sensor array, which means that many different kinds of sensors are present, and some of them respond to any given molecule, and others respond to other molecules. The point is that if you only had one sensor, you couldn't tell one molecule from another, or even reliably identify a single type of molecule, but the pattern of responses from the many different receptors is unique to each smell, including smells which arise from mixtures of substances

 

Perhaps a bit of reading on cross-reactive-sensor-arrays would help you understand?

 

THIS review is quite in-depth, but perhaps the introduction might enlighten you a little

 

Also try googling "artificial nose"

[Ashish]

can u tell me little more on this

[DrP]

I'm no expert and can't go into the detail that hermantrude can, but in laymans terms, if you want it simpler..

 

There are receptors in the nose. Actual molecules (gass, vapouror individuale particles) from the material itself are breathed into your nose and settle on your receptors. Your brain works out what the 'smell' is by processing the vibrational and shape like information the receptors give it about the molecule being smelt.

 

(I am aware that this could be explained alot better and may even be slightly wrong.....but I think this is the general gist of it and I hope it is an easy to understand model of what happens in short).

[hermanntrude]

I'm no expert and can't go into the detail that hermantrude can, but in laymans terms, if you want it simpler..

 

There are receptors in the nose. Actual molecules (gass, vapouror individuale particles) from the material itself are breathed into your nose and settle on your receptors. Your brain works out what the 'smell' is by processing the vibrational and shape like information the receptors give it about the molecule being smelt.

 

(I am aware that this could be explained alot better and may even be slightly wrong.....but I think this is the general gist of it and I hope it is an easy to understand model of what happens in short).

 

this serves as a very simple explanation but the truth is more complicated than this.

 

The receptors don't relay much information at all themselves.

 

let's say you have four receptors (there are actually thousands). the receptors are called A,B,C and D. Receptor A will respond to onions, cabbage and milk. receptor B will respond to onions, cream, and the smell of pine trees. receptor C will respond to the smell of onions, carrots, cabbage. receptor D will respond to onions, shallots, and the smell of mown grass.

 

Think now about what happens when you smell an onion. Receptors A,B, C AND D, will all respond. Your brain receives these responses, and through training, knows that this is the smell of onions. Remember that you are NOT born with the knowledge that onions will give this response. you have to learn about smells. the same is true of artificial noses... you have to train them to recognise smells.

 

So when you smell pine trees, receptor B will respond, but none of the others. When you smell cabbage, receptors A and C will respond. If you smelt a mixture of milk and cream, you might judge the respective amounts of each by comparing the strengths of responses from receptors A and B.

 

This is the kind of thing which occurs in olfactory sensing, although it's FAR more complicated than that, because there are so many receptors and so many smells, many of which are the smell of multiple chemicals anyway.

 

it's not really the individual receptors' response which tells us what it is we're smelling, but the pattern of responses and their respective strengths.