Smell Health Dictionary

One of the 5 senses. In the nose, hair-like projections from smell receptor cells lie in the mucous membrane. When the receptors are stimulated by certain molecules, they transmit impulses along the olfactory nerves to the smell centres in the limbic system and frontal lobes of the brain, where smell is perceived.

Possible causes of loss of the sense of smell include inflammation of the nasal membrane, as in a common cold; cigarette smoking; hypertrophic rhinitis,in which thickening of the mucous membrane obscures olfactory nerve endings; atrophic rhinitis, in which the nerves waste away; head injury that tears the nerves; or a tumour of the meninges or nasopharynx. The perception of illusory, unpleasant odours may be a feature of depression, schizophrenia, some forms of epilepsy, or alcohol withdrawal. smelling salts A preparation of ammonia that was used in the past to revive a person who felt faint.

The sense of smell is picked up in what is known as the olfactory areas of the NOSE. Each of these is about 3 square centimetres in area and contains 50 million olfactory, or smelling, cells. They lie, one on either side, at the highest part of each nasal cavity. This is why we have to sni? if we want to smell anything carefully, as in ordinary quiet breathing only a few eddies of the air we breathe in reaches an olfactory area. From these olfactory cells the olfactory nerves (one on each side) run up to the olfactory bulbs underneath the frontal lobe of the BRAIN, and here the impulse is translated into what we describe as smell.