In 2007, a geneticist at U Washington School of Medicine confirmed that pain and itching are indeed two different sensations. Through research on mice, Chen found that a class of mutated genes can inactivate protein , a mouse spinal nerve , called "GRPR". This protein can ensure that the neural signals from specific neurons in the skin can be continuously transmitted and eventually reach the brain. However, in mutant mice, this neural signal cannot be transmitted properly.
Feng found that mutant mice could sense pain normally. When scientists use needle tips to mutate the paws of mice, their reactions are the same as ordinary mice, trying to stay away from the needle tips. But when scientists applied a chemical that causes itch to mutant mice, the mice had little response. This mutation of
cannot sense itching in mice, because itching signals must be conducted by neurons containing GRPR protein in the spinal cord. However, mutant mice can still perceive pain, indicating that the transmission pathway of pain signals is different from that of itch signals. In other words, pain and itching are two different feelings.
Although pain signals and itching signals are transmitted to the brain through different neural pathways , they actually have the same function when they reach the brain. Both of these neural signals serve as an alarm, telling the brain that there are foreign objects or dangers, allowing us to respond quickly. Therefore, itching and pain are very different from other feelings.
If your hand touches a soft blade, the touch will be recorded by the sensory nerve. Almost at the same time, the sensory nerve sends neural signals to the sensory center of the brain. Then, unless the frontal lobe of the brain thinks the body should respond in a specific way, we will do nothing. However, if your hand touches thorny nettle while brushing leaves, the itchy nerves will be activated immediately and send nerve signals to the brain. When these signals reach the brain, the brain reacts in a series of ways.
First, the sensory center of the brain recognizes nerve signals and produces itching. Then, the itchy sensation will spread to the frontal lobe. However, before the frontal lobe senses itching and commands the body to respond, the itchy nerves are already affecting your brain—our moods will worsen, stress levels will rise, and we have an instinctive impulse to tick up the itch, trying to relieve this uncomfortable feeling.
, like pain, the purpose of itching is to allow us to unconsciously remove our hands from the nettles quickly, thereby reducing the probability of redness and blisters in the skin. Of course, this discomfort can also keep us away from nettle in the future.
(Article excerpted from "Singularity Science" 2023 magazine subscription Popular Science Magazine http://www.zazhipu.com/2027353.html)
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