Using a Novel technique, researchers at Karolinska Institutet in Sweden have been studying the brain and how our central nervous system judges a smell to represent danger. Our brain can distinguish between millions of different smells because of the olfactory organ. The olfactory organ is located in the walls of the upper part of our nasal cavity. Most of these smells are associated with a threat to our body’s health. After inhaling an odor it takes between 100 and 150 milliseconds to reach the brain. The detection and reaction of a smell has always been an important factor in all mammals’ survival. The researchers at Karolinska Institutet’s study has proven that negative smells are associated with unrest and are processed earlier in the brain than positive smells.Anatomy and physiology of animals Olfactory organ the sense of smell

Unpleasant smells trigger a physical avoidance response. The avoidance response has always been seen as a conscious cognitive process but recent research has proven that it is actually an unconscious and rapid process.

For a long time it has been a mystery as to which mechanisms in the brain are involved in the process of associating an unpleasant smell with danger and causing avoidance behavior in humans.The researchers at Karolinska Institutet have come up with a process in which you can measure signals from the olfactory bulb. The Olfactory bulb transmits signals to the part of the brain that controls avoidance behavior. Avoidance behavior can be described by a number of patterns, one of those patterns being a pattern of protective reflexes.

Three experiments were conducted where participants were asked to give their opinions on six different smells. The associate professor at the Department of Clinical Neuroscience shares that “the results suggest that our sense of smell is important to our ability to detect dangers in our vicinity, and much of this ability is more unconscious than our response to danger mediated by our senses of vision and hearing.” 

In AP Biology class, we learned about protein receptors. Smelling relies on protein receptors recognizing specific ligands. Humans are able to distinguish thousands of different compounds by smell. The shape of a molecule is most responsible for its smell rather than its physical properties. Thus, the smell relies on the interaction with a binding surface, usually, a protein receptor. 

It is so interesting how our bodies can distinguish the smallest differences in molecules. These differences can change the smell of something completely. These smells also help to determine our emotions. Smelling something bad can make us uneasy or feel unsafe while smelling something good can bring us joy. Can you think of a scenario where a smell made you feel unsafe?

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