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Looking for olfactory passwords: How do you know how different odors are recognized?
Smell, the sense of smell that is often overlooked in our daily lives, plays an important role in the environment.Whether it’s tasting a cup of mellow coffee or sensing the tempting smell of dinner, our olfactory perception comes from subtle chemical reactions.Recent research has in-depth discussions on the structure, function and evolution of olfactory receptors, revealing the mystery of how humans recognize various odors.
Olfactory receptors (ORs) are the largest multigene family in the human body, consisting of about 400 genes, corresponding to more than 10,000 odor molecules.
Function of olfactory receptors
Olfactory receptors are chemical receptors located on the cell membrane of olfactory neurons, mainly responsible for detecting odor molecules.Once the odor molecules bind to the receptor, neural pulses will be triggered, which will then convey odor information to the brain.Olfactory receptors are not only present in the olfactory system, but are also expressed in other cells, including sperm cells, which sense odors to help locate eggs.
Mechanism of Odor Recognition
Olfactory receptors can develop affinity for a variety of odor molecules, and a single odor molecule may also bind to different olfactory receptors.This mechanism involves structural changes in the receptor and initiates the internal G protein, which activates the adenylate acylase, converting ATP into cyclic AMP (cAMP).This process causes calcium and sodium to enter the cells, triggering depolarization of olfactory neurons, and ultimately creating action potentials.
"The response of a mouse's olfactory receptor to certain odors shows that copper is crucial in odor recognition."
Evolution and diversity of olfactory
In vertebrates, the gene family of olfactory receptors covers many species, and studies have shown that these genes evolved through gene replication and gene conversion.Changes in human olfactory receptor genes reflect the differences between us and other mammals.Although we have about 400 functional olfactory receptor genes, about 600 genes are due to pseudogenes, indicating the complexity and flexibility of olfactory sense.
Controversy over vibration theory
Another theory for the olfactory mechanism is the vibration theory, which proposes that olfactory receptors may be identified by sensing the vibrational energy level of the molecule rather than the structural pattern.However, this view remains controversial, with many research results pledging the effectiveness of this theory, showing that traditional structural functional theory still has higher explanatory value.
Study points out: "Compared with other mammals, the vibration theory in perceptual operation mechanism does not seem to be applicable to humans."
Emotions and Memory of Olfaction
Smell is not just a basic sensory experience, it is deeply rooted in emotions and memory.A particular scent may evoke our memories or emotions because the olfactory system is directly connected to the brain's limbic system.This makes smell one of the "most primitive" senses and the most likely sense to trigger emotional resonance.
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Through in-depth study of olfactory receptors, we have a clearer understanding of the mechanisms of odor recognition, which may help develop new technologies and treatments.Will human olfactory abilities be challenged with technological advancement?
