The nose and brain together can distinguish between 2000 to 4000 different smells. We identify smell using the olfactory sensors which are located at the top of the nasal cavity inside of the olfactory bulb. The olfactory receptor cells are neurons equipped with olfactory hairs. These are long cilia that protrude from the nasal epithelium and are continually bathed by a layer of mucus secreted by underlying glands. When the receptors are stimulated by chemicals dissolved in the mucus they transmit impulses along the olfactory filaments. They collectively make up the olfactory cortex of the brain. There is where the interpretation of smell occurs. The odor pathways are closely related to the limbic system, This is the reason that we can remember and associate smells with certain places, people, or things. The olfactory neurons can adapt rather quickly when they smell a certain odor that is why they can stop reacting to certain odor after being exposed for a long time.

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Physiology- The relationship between smell and taste

Smell and taste meet up at the back of the throat. When you taste something before you smell it, the smell lingers internally up to the nose causing you to smell it. Both smell and taste use chemoreceptors, which essentially means they are both sensing the chemical environment. A lot of the taste sensation comes from the same receptors in the nose you use to smell. When you eat something and you can tell the difference between sweet and bitter, without the sense of smell you wouldn't be able to determine which food was bitter or sweet because we identify the food based on smell.