Smelling (Olfaction)
Art & Research: Sarah J. Lee
Further Reading Literature: Kadir Özler
Introduction to smelling
Has a certain smell ever taken you down memory lane?
When we smell, we are picking up odorant molecules in the air.
Odorants
The odorant molecule travels into the nose and up the nasal passage, which is line with little hairs called "cilia."
The odorant's destination is at the top of the nasal cavity, where it must reach a membrane called the "olfactory epithelium" (olfactory means smell) (Khan Academy).
Olfactory pathway
The epithelium is composed of regular cells that sandwich sensory neurons, specialized cells that signal to the brain when they detect a specific odorant (Khan Academy).
Sensory neurons have nerve endings, long projections that make contact with the odorant (Khan Academy).
Upon closer inspection, these sensory neurons actually connect to the olfactory bulb, a part of the brain that directly picks up the signals sent by these cells (Khan Academy).
A thin layer of bone, the cribriform plate, separates the nasal cavity from the brain (Khan Academy).
These sensory neurons "wire" through small holes in the bone, up to the olfactory bulb (Khan Academy).
Sensation of odorants
A specific odorant can only bind to a specific receptor on a specific neuron.
When we smell many odorant molecules of the same kind, each one binds to a sensory neuron of the same kind.
These sensory neurons will converge at a mitral cell, located in the olfactory bulb (Khan Academy).
The mitral cell acts as a middleman between sensory neurons in the brain (Khan Academy).
Smell signaling to brain
The mitral cell "dispatches" the signals to the brain.
Olfaction is the only sense that bypasses processing in the thalamus (a brain region), and heads straight to the "limbic system" (Khan Academy).
The limbic system is a collection of brain structures responsible for processing emotion and memory (Khan Academy).
Memory of smells
This odorant is connected with a specific memory (Khan Academy). More specifically, of where the scent was smelled (Khan Academy).
The emotions associated with the odor can come rushing back, like the first time you smelled it and take you on that trip down memory lane.