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Historical Adventures in the Sense of Smell: How did the earliest scientific research reveal the secrets of smell?
The sense of smell, or smell, is one of the unique human senses. Through this sense, we can perceive various smells. The functions of the sense of smell include identifying the deliciousness of food, detecting dangerous odors, and identifying sexual information between people, and plays an important role in taste. The sense of smell is activated when an odor binds to receptors in the nasal cavity, sending signals through the olfactory system.
These signals converge through clusters of neurons (glomeruli) and are transmitted to the olfactory bulb, where sensory input begins to interact with brain areas responsible for olfactory recognition, memory and emotion.According to current research, the operation of the olfactory system is closely related to a variety of neural structures, and its perception process still contains many unsolved mysteries.
However, the performance of normal olfaction may be disrupted by a variety of factors, including damage to the nose or olfactory receptors, loss of smell (anosmia), upper respiratory tract infections, traumatic brain injury, and neurodegenerative diseases.
The history of scientific research on smell
Early scientific research on olfaction dates back to 1898, when Eleanor Gamble published a detailed doctoral thesis exploring olfaction in comparison with other modes of sensory stimulation and suggesting that olfaction has a lower intensity-discriminating ability. Lucretius, the Epicurean philosopher in ancient Rome, believed that differences in smells originated from "atoms" of different shapes and sizes, which is similar to the modern understanding of smell molecules.
Many contemporary researchers, including 2004 Nobel Prize winners Linda B. Buck and Richard Axel, have successfully cloned olfactory receptor proteins and mapped olfactory molecules to specific receptor proteins.
There are about a thousand genes encoding olfactory reception in mammals. However, functional genes are only a part of them. The number of active olfactory reception genes in humans is much lower than that in other primates and other mammals. Each olfactory receptor neuron usually expresses only one functional olfactory receptor. This "key-lock" system is the basis of odor recognition: if a certain odor molecule can "fit" the receptor, the associated neuron will There will be a reaction.
Function of smell
The influence of taste
The perception of taste is actually a synthesis of various sensory information such as hearing, smell, touch and taste. Especially during eating, the tongue changes the position of the food to release odor molecules. These odors enter the nasal cavity when exhaling, enhancing the taste experience.
Smell, taste and chemoreceptors (trigeminal receptors) work together to form our overall perception of food flavor.
The association between social behavior and smell
Humans and many animals are able to identify potential sexual partners through scent. The study found that major histocompatibility complex (MHC) genes in the genome have a direct impact on pairing preference. Specifically, offspring from parents with different MHC genes generally have stronger immune systems. When women use hormonal contraceptives, they may change their partner preferences, thereby affecting each other's genetic diversity.
Guide reactions and behaviors
Some animals use scent trails to guide their actions. For example, social insects use scent to leave paths to food sources, and tracking dogs can also use scent to track prey. Tracking strategies among different species have been widely studied, such as chemotaxis, wind direction, etc., and these behaviors are affected by the surrounding environment.
Genes and smell
The sense of smell is marshmallow. The main reason for the difference in each individual's perception of smell is genetic differences. Although the gene family involved in odor reception is one of a kind in the human body, the genes that specifically correspond to specific odors are limited to a few.
For example, the OR5A1 gene and its variants are thought to be involved in our ability to smell beta-ionic ketones.
Humans' ability to smell is relatively insignificant when compared to that of some animals, especially canines. It is estimated that a dog's ability to smell is about a hundred thousand times greater than that of a human being. This allows dogs to detect odors in the air that are extremely thin to humans.
The ability of the human sense of smell
Although early research suggested that humans can distinguish only 10,000 unique odors, recent research shows that the average person can distinguish more than 1 trillion unique odors. This conclusion has led the scientific community to re-evaluate human olfactory abilities and propose higher standards of discrimination.
This reminds us once again that the huge number of olfactory receptors in the olfactory system cannot be underestimated.
However, the authors also point out that the ability to distinguish odors is not equivalent to being able to consistently accurately identify those odors, and during the identification process, subjects are often unable to pinpoint specific odor molecules from a complex of multiple odors.
As the study of smell becomes more in-depth, we begin to understand that smell is not only a physiological function, but also a complex system that connects emotion, memory and behavior. How does this affect our understanding and perception of the world around us?
