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24 September 2014
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Fact files

Nervous system - Smell

Receptors: Olfactory receptors

Smell and taste: Food tastes bland without your sense of smell

Linked to memories: The nerves involved in smelling are linked to the emotional centre of your brain

Warning mechanism

Your sense of smell warns you of dangers such as smoke and poisonous gases. It also helps you appreciate the full flavours of food and drink. Your sense of smell is 10,000 times more sensitive than your sense of taste.

Olfactory receptors

You are able to detect thousands of different smells. The receptors that sense smells are called olfactory receptors. They occupy a stamp-sized area in the roof of your nasal cavity, the hollow space inside your nose.

Tiny hairs, made of nerve fibres, dangle from all your olfactory receptors. They are covered with a layer of mucus. If a smell, formed by chemicals in the air, dissolves in this mucus, the hairs absorb it and excite your olfactory receptors. A few molecules are enough to activate these extremely sensitive receptors.

Linked to memories

When your olfactory receptors are stimulated, they transmit impulses to your brain. This pathway is directly connected to your limbic system, the part of your brain that deals with emotions. That's why your reactions to smell are rarely neutral - you usually either like or dislike a smell. Smells also leave long-lasting impressions and are strongly linked to your memories. The scent of mown grass, for example, might remind you of a childhood summer holiday, and the smell of chocolate chip cookies may make you think of your grandmother.

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