OUR SENSE OF SMELL:
IT'S MORE IMPORTANT THAN WE THINK
How does our sense of smell work?
Our sense of smell is 10,000 times more sensitive than any of our other senses such as touch and taste. When we smell, the reaction goes straight to the brain but if we touch or taste anything, those senses must travel through neurons and the spinal cord before it reaches the brain. Here’s how smell works:
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Odor chemicals that are floating in the air dissolve in the mucus in the nostrils.
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Once the chemicals have dissolved in the mucus, olfactory receptor neurons detect the odor and these neurons can detect thousands of different odors.
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The neurons then transmit the odor information to the olfactory bulbs.
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The olfactory bulbs then send information to parts of the brain that influence emotions, memories, and conscious thought.
-These parts of the brain perceive the odors which triggers memories and remind us about people, places, and events. (Rodriguez-Gil,2004)
Humans are microsmatic, meaning that our sense of smell is not keen to our survival. However, there are many animals that are macrosmatic because their sense of smell is very important to their survival. Olfaction aids in survival for many species by helping them orient in space, mark territory, and guide to specific locations for finding other animals and food sources. Macrosmatic animals use olfaction in sexual reproduction because it triggers sexual behavior. Even though humans are microsmatic, we release pheromones that can causes phenomena such as menstrual synchrony in women. Pheromones affect the physiology and behaviors of others. Menstrual synchrony occurs when women’s menstrual cycles sync because they are together daily (Goldstein, 2010).
Most people do not give the amount of credit to our sense of smell that it deserves. We can survive without our sense of smell, but olfaction helps us identify spoiled food to avoid being ill and alerts us to smoke from a fire or leaking gasoline (Goldstein, 2010).
With identifying odors, there is a “presence” threshold and a recognition threshold. We can detect the presence of an odor when it is near the “presence” threshold, but we cannot sense the quality of the odor unless it is at the recognition threshold. We can identify an odor’s quality when concentration is increased by 3 times or more above the threshold concentration (Goldstein, 2010).
Humans can discriminate between about 100,000 different odors, but have a difficult time actually identifying specific odors when they are unaware of the odor’s substance. When asked to actually identify the substance, we are only right about the substance half the time. A study by Desor and Beauchamp (1974) demonstrated that we could get better at identifying these substances with practice. They presented participants with the names of the substances at the beginning of the experiment and reminded them of the correct names when they were wrong. After practice, the participants were able to identify 98% of the substances (Goldstein, 2010).
The olfactory mucosa contains the receptors for olfaction and is located on the top of the nasal cavity and below the olfactory bulb. Olfactory receptor neurons are the cells that contain the olfactory receptors. Olfactory receptor is a protein molecule that consists of strings of amino acids and there are about 350 different types (rats have about 1,000!). Of the 350 types, there are about 10,000 of each type. Activation of olfactory receptors can occur from odorants by following directly in a stream of inhaled air or they can become attached to molecules called olfactory binding proteins that transport that information through mucosa (Goldstein, 2010).