Chemical Constituents And The Sense Of Smell
Our sense of smell is a fascinating subject that has kept people throughout history intrigued and for good reason.
Ancient writings describe Egyptians incorporating fragrant plants into mixtures for religious ceremonies and personal fragrances. European ancient medical texts maintained that odors could directly affect those who inhaled them.
Modern science can now prove that odors can impact emotions and that different organs in the body, such as our brain and lungs, are engaged when aromas are inhaled.
Smell, or olfaction, is one of the most primal senses in the mammalian brain
The Nose
Smell is a chemical reaction. When we inhale something, our brain decodes a “message” from the odor molecules entering the nose.
This is possible because the nose is covered by cilia of olfactory sensory receptor neurons within the olfactory epithelium (the membranes in the nose) that sends messages through the olfactory nerve to the olfactory bulb. This bulb is connected to specific parts of the brain, such as the amygdala and hippocampus, which play important roles in odor recognition, emotional responses, learning, memory and other functions.
** Arisi et al 2012
Aromas can have instant psychologic and physiologic effects (Hinton 2004), and sometimes just thinking about a smell can be as powerful as actually smelling it (Betts 1996).
The Nose and The Limbic System
The limbic system (LS) is a complex combination of brain structures found below the cerebral cortex. Its main parts are the amygdala, hippocampus, anterior thalamus, and hypothalamus. The impact of smells on the central nervous system was noted as early as 1923, when scientists saw how odors produced immediate effect on respiration, pulse and blood pressure. **Hinton 2004
In some animals, the LS it’s considered as the smell brain because these animals depend on their sense of smell for survival.
When it comes to smell and the LS, the amygdala and the hippocampus play the biggest role.
An almond-shaped group of cells, located under the temporal lobe. It is thought to play a role in processing emotion, the formation of emotional memory and emotional response **Arisi 2012
It controls fear, anxiety and aggression.
The hippocampus is associated with learning and memory. It is thought to be the storage area for new experiences before they become permanent memories stored in the cerebral cortex.
Studies show that some odors can arouse emotions or recall memories
**Kadohisa 2013
The Nose and Lungs Interaction
Aside from acting as the first part of the olfactory system, the nose also warms and filters the air before it reaches the lungs. The lungs have a big surface area and it is connected to the blood system via the alveoli. The alveoli are tiny, balloon-shaped air sacs sitting at the very end of the respiratory tree, arranged in clusters throughout the lungs whose function it is to exchange oxygen and carbon dioxide molecules to and from the bloodstream.
