The Mechanics of Smelling
When the scent of something is inhaled, the odour molecules float to the back of the nasal cavity.
Here they dissolve in the moist environment, and in this form unite with receptor, or olfactory cells.
The olfactory cells then trigger off electrical signals via the nerve pathways to the olfactory bulb in the brain.
Most of the essential oil molecules that have triggered the system are breathed out, although some will enter the blood stream via the lungs.
Only eight molecules of an odoriferous substance are needed to trigger the smell mechanism.
The areas of the brain to which messages concerning smell are sent are the cerebral cortex and limbic system.
The limbic system controls many vital activities, such as sleep, sexual drive, hunger, and thirst as well as smell.
This is also the area of the brain that relates to emotion and memory, and thereby gives the clue to the link between smell, emotion and memory.
Odours also connect with the part of the brain called the hypothalamus, which controls the endocrine system and nervous system.
Through this mechanism the brain comes into direct contact with the outside world.
The fading of a scent occurs when all the receptors are full, but after ten minutes or so they are vacated and can be reoccupied, causing the scent to ‘come back’.
This explains why we may fail to notice a scent after a while, while another person just entering the same area may comment upon it.