Andrew Watkins

Also known as Olfaction, smell is a form of chemoreception, which means that it is activated by chemical stimulants in the air. In this way smell is directly linked to taste, in fact it is both of these senses that create flavors.

The nose is a hollow passage that enables breathing and smell. The nose warms air and filters out any harmful particles in the air.

There are two theories that explain how we smell. One is based on shapes of molecules in the air, the other is based on vibrations of these same molecules.

The shape theory states that smell operates on a “lock and key” mechanism. This means that receptors are stimulated when the correct molecule fits the receptor.

The vibrational theory is a little more complex and is based on wave lengths that emit from each molecule. All molecules that you can smell are made up of atoms, which can be identified by the amount of vibrations they give off.  In some sense you can think of molecules as musical instruments.  Each atom will only play its designated note and are put together to form molecules, or in this sense chords.  So just as a musician would recognize C, E, G as C major our brains can interpret certain combinations of atoms as the smell we perceive.  Because atoms always vibrate with the same frequency we can identify what a certain atom is with certainty by looking at the vibrations it gives off.  The two things that can perform this task are a device called a spectroscope and the human nose. 

Without a question some species are blessed with a stronger sense of smell than others. Part of this is because some animals rely heavily on smell for survival while others do not. For example we, as humans, have developed in a way that puts more focus on senses such as sight and hearing, therefore we don’t have as highly developed sense of smell as animals who rely on smell for their survival. To put it into perspective a bloodhound has 4 billion olfactory receptors while humans have only 12 million.

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