It smells a bit, but you get used to it after a while

There is a word called "empathy", but there are many things in the world that cannot be empathized with. For example, everyone's sense of smell is different. Some people cannot smell their own foot odor or body odor, but the people around them can't stand it.

Regarding the magic of smell, there is an ancient saying: "If you stay in a room full of orchids for a long time, you will not smell the fragrance; if you stay in a shop selling abalone for a long time, you will not smell the stench." Why is this so? Can the nose also feel tired? Today, let us explore the magic of smell together.

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1

Does olfactory fatigue really exist?

The reason why people can identify certain things in this complex world is that they often rely on their sense of smell to make such judgments.

The olfactory bulbs that sense odors are located on the olfactory epithelium at the back of the human nasal cavity. Odor-bearing particles in the air enter the nose and stimulate the olfactory epithelial cells, which then generate electrical signals. These signals are then transmitted through neurons, first to the olfactory bulbs, and then to the brain. When you smell an odor, that is when your brain receives the signal.

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However, the signal transmission is not very accurate in many cases. Specifically, in life, people with body odor cannot perceive the odor on their bodies, and people who stay in the garden for a long time cannot quickly determine the fragrance... Such a phenomenon is vividly called "olfactory fatigue."

Specifically, under normal circumstances, when odor molecules are attached to specific proteins on receptor cells (guanine nucleotide protein-coupled receptors), sodium ions and calcium ions flow into the cells, generating a potential difference and a perceptible impulse (depolarization) on the cell membrane. The pathway for the influx of sodium ions and calcium ions is the cyclic nucleotide-gated ion channel (receptor cells convert external electromagnetic or chemical signals into intracellular electrical signals. In this process, the receptor cells are controlled to produce cation influx, thereby generating bioelectric signals).

When people are constantly in an environment and smell a certain odor, the olfactory neurons respond to the odor and depolarize, and the second messenger mediated by G protein (a type of signal transduction protein that can bind to guanosine diphosphate and has GTP hydrolase activity) activates adenylate cyclase, increases the concentration of cyclic adenosine monophosphate in the cell, and then opens the cyclic nucleotide-gated ion channel. Next, the rapid influx of calcium ions will trigger a chemical cascade reaction that triggers olfactory fatigue, causing the cyclic nucleotide-gated ion channel to close and making similar odor molecules unable to activate the receptors, and no longer send electrical signals for the brain to perceive the smell.

Eat two pieces of stinky tofu and you won't smell the stench anymore

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In other words, olfactory fatigue occurs because the olfactory nerves are repeatedly stimulated by the same odor. If the concentration of the odor does not increase, the receptors associated with the molecule can no longer be activated by similar molecules due to a series of cascade reactions, and the brain's excitement for the smell is also reduced, and the reaction becomes slower. So over time, some people can no longer smell their own odor, and can no longer quickly respond to fragrance and odor, so-called "getting used to it by smelling it for a long time."

In fact, this is the result of evolution, which can make our body insensitive to continuous stimulation, prevent the nervous system from being overloaded, and respond to unusual, special, and new stimulation. It is also very simple to solve the problem of olfactory fatigue, just go to a new environment. If you stay in an environment with birds singing and flowers blooming for a long time, you may not be able to smell the fragrance for a while, but as long as you go out for a while and re-enter, your nose can quickly capture the fragrance of the flowers again.

2

What is anosmia?

In addition to olfactory fatigue, the problem of anosmia has also attracted people's attention in recent years. "Spring breeze brings fragrance to flowers and grass" and "late melons have a lingering fragrance". The sense of smell is a tool for people to perceive everything. However, there are also some patients with "anosmia" who lack this ability.

This group of people either lack a normal sense of smell or cannot perceive odors. Some people's anosmia may be temporary, while some people are troubled by it for life, such as traumatic anosmia. There are many causes of anosmia, including acquired factors such as inflammation of the nasal mucosa, blocked nasal cavity, damage to the temporal lobe of the brain, and some people are born without a sense of smell.

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This disease has caused immeasurable impact on their lives. The most common one is that it brings inconvenience to their lives. They cannot feel the refreshing aroma, and they also lack the perception of "fragrance" in their food.

Even worse, it can threaten their lives. The sense of smell can sometimes help us avoid risks. When we smell gas, normal people will react quickly; when they smell the strange smell of spoiled food, they will throw it away. But people with olfactory impairment cannot rely on their sense of smell to identify and avoid such risks.

Not being able to smell a gas leak is undoubtedly very dangerous

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In addition, this disease can induce a series of psychological problems. In order to blend in with the surrounding environment, many patients will conceal this fact and even pretend that they can smell. People with olfactory disorders are very concerned about their body odor and are usually accompanied by social anxiety. Unable to use their sense of smell in interpersonal communication, they need to rely on others to help identify odors. The lack of autonomy makes them quite troubled and frustrated, and these psychological problems will persist for a long time.

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Current studies have shown that anosmia can increase stress and depression levels in patients. A British study showed that people with olfactory impairment had a higher rate of depression and anxiety. Among these people, 92% had difficulty eating, 57% had been isolated, 54% had interpersonal communication difficulties, 45% felt anxious, and 43% were depressed. At the same time, female patients have more problems with social and family dysfunction than male patients. Therefore, in life, we cannot ignore this group, and it is essential to pay attention to and care for people with olfactory impairment.

Smell is an extremely important sense for humans. Many things emit unique smells, and we can distinguish them by smell. In people's experience of perceiving smells, every moment is a personal olfactory memory.