Once “trapped,” the odor molecule binds to a specific GPCR in the olfactory receptor neuron - like a “shape” fitting into a “mold.” From there, a cascade of chemical reactions will lead to the opening of ion channels in the olfactory receptor neurons. Our nostrils have mucus in them which are able to “trap” this pinene like a fly in honey. So, what’s happening here?įor a start, the “Christmas tree” scent is actually pinene, a volatile chemical which comes from pine trees. Your brain has primed you to expect a Christmas tree, and low and behold, you turn the corner and a bushy, green Christmas tree is standing in the family room. You don’t see a Christmas tree, but you smell one. The first thing you smell when you walk in the door is a Christmas tree. However, the basic pathway can be illustrated by the following: It is winter break, and you pull into your parents’ driveway. Still, how do these infamous GPCRs recognize odor molecules so specifically? This aspect of the olfactory system is still not completely known. Human nasal cells contain roughly 400 types of olfactory GPCRs, whereas those of some mammals such as dogs contain more than 1,000, making them keen at distinguishing odors - this also means that there are scents in human environments that we cannot even smell. Located in the nasal epithelium of the nostrils, GPCRs are diverse and abundant in the olfactory system, with each latching on to many different scents and triggering a unique response. Luckily, biology is good at this, and with the help of proteins known as G-protein coupled receptors (GPCRs), we are able translate the chemistry of odors in the air into electrical signals in the brain. The science of scent is not as simple as it sounds, as it starts with the brain converting sensory stimuli in our environment. Without a sense of smell, we would not be able to protect ourselves from toxic odorants, such as propane leaking from a kitchen stove, or enjoy pleasurable smells, such as fresh baked apple pie. While the olfactory system is often outshined by the neuroscience of its cousins, such as how the brain sees or how the brain hears, how the brain smells is imperative to our quality of life. Taking its name from the Latin word olfacere, which means "to smell,” the olfactory system is an amusement park of neurons contained in the brain which allow it to identify and differentiate the smells of our environment. The brain can then respond with a cocktail of emotion - and action - from avoiding food that has spoiled to sensing a fire from the smell of smoke.īut how is the brain able to detect cues from our environments? And more so, why is it that certain scents bring back vivid memories, some of which may date back to childhood?īehold the olfactory system. The human nose has a unique way of picking up the scents of our surroundings and communicating these scents to the brain. Or perhaps it's the whiff of fresh pine in HomeGoods that reminds you of Christmas, or the scent of Axe body spray in CVS that brings you back to those awkward middle school days. Suddenly, you remember summer vacations spent on the Ocean City boardwalk. The smell of funnel cake wafts through the air. How Your Nose Knows: The Science of Smell and Memory
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