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When
one smells a flower, its fragrance enters the nose
with a breath. Its scent is made up of minute aromatic
molecules. At the top and on both sides of the upper
nasal cavity is the olfactory epithelium, which
is covered with a thin layer of mucous membrane.
When in the nose, the aromatic molecules migrate
through the mucous membrane to the underlying tissue
of nearly 10 million olfactory nerve cells. Each
nerve cell carries a bundle of tiny hairs that have
unique receptor cells to fit each aromatic molecule
shape. These receptors are highly sensitive and
capable of carrying an immense amount of information.
The human nose can detect up to 10,000 different
odors at minute concentrations. The
receptors then transmit the odor along the nerve
fibers, in the form of electrical impulses, to
the olfactory bulb, which in turn passes the stimulus
to other relevant parts of the brain which is
translated into physiological and behavioral effects,
and finally into an olfactory experience. The
scent passes through the limbic system where feelings
and instincts are interpreted.
In
Aromatherapy and the Mind, Julia Lawless
states: “Unlike visual or oral stimuli,
which are processed by the cerebral cortex, odors
pass straight to the olfactory bulb where they
are given an immediate feeling value. This also
accounts for why we can be affected by odors without
even being conscious…the information has
bypassed the cerebral cortex and entered directly
into the innermost ‘control centers’
of the limbic system.”
Interestingly,
Lawless also explains that “odor stimuli
in the limbic system or olfactory brain release
neurotransmitters – among them encephaline,
endorphins, serotonin, and noradrenaline. Encephaline
reduces pain, produces pleasant euphoric sensations,
and creates a feeling of well-being. Endorphins
also reduce pain, stimulate sexual feelings, and
produce a sense of well-being. Serotonin helps
relax and calm, and noradrenaline acts as a stimulant
that helps keep you awake."
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