From out of the dark room, face to the sun, the mood suddenly big Yue, stretch, stretch, look up at the sun, ready to express what feelings. Suddenly, the nose began to feel intolerable itching, you begin to take a deep breath, opened his mouth, and finally, a stirring sneeze played out.
You encountered this situation?
A third of people will answer: Yes.
This is called the Sunshine excited sneeze photic sneeze reflex (light sneeze reflex). There is also a more formal medical name, called ACHOO (autosomal dominant compelling helio-ophthalmic outburst) syndrome ( somatic dominant hereditary optic daylight forced eruption syndrome). A very long name. See, or inherited.
That's why so many people have such a reflection of it? How to explain it?
In fact, this problem has troubled mankind for thousands of years.
Great Aristotle The Book of Problems on the inside describe the problem. He asked: "Why is the sun makes me sneeze?" It seems that the great Aristotle also belong to 1/3. He speculated might be sunlight let nose, fever, led to sneeze.
After about 2000, early 17th-century British philosopher Francis? Bacon read the great Asian Guinness little more of this book, start thinking (Thinking philosopher is love). But rare is that Bacon not only think, but also began to experiment. His experiment is very simple, from out of the dark room, his eyes closed. Eyes closed is not closed, the nose still heat ah. If it is because the heat cause sneezing nose, close your eyes and it should also be sneezing is. The results do not look know, no sneezing occur. This simple experiment easily negate the great Aristotle conjecture. And usually we just go out on the moment of sneezing, nose impossible so quickly become hot. That in the end why? Philosopher Francis? Bacon of course, can not be answered. He guessed the glare of the sun cause watery eyes and nasal lacrimal tears flow into the nasal cavity, nose irritation and sneezing.
That sounds reasonable. Since then, people believed that. Until the 19th century, the development of modern medicine, the rapid progress of various physiological testing methods and tools, quickly overturned this argument. Because a test, they found, to see the sun from this time period is too short to play sneeze, sneeze reflex too quickly. Watery eyes, etc., from the narrow nasolacrimal duct flow into the nasal cavity, the day lily is cold, and so get where sneeze ah.
That in the end how to explain it?
Knowledge of neurological function. Now most of the mainstream neuroscientists agree because nerve signals cross in the brain leads to the reflection.
Specifically how it happened?
Our first sneeze nasal mucosa to stimulate the feeling of foreign body, the brain commands the nose, the foreign matter discharge needs to go, do not let it stay in the nasal cavity. So this nasal sensory signals to the brain through the trigeminal nerve. The trigeminal nerve has three branches, twelve cranial nerves of the first five, feeling responsible for collecting face nose mouth, but also muscle movement control tube, also responsible for the nasal cavity of the sneeze reflex. It so happened that on the way back to the trigeminal nerve in the brain, nerves and it has a cross. The cross is the optic nerve, the nerve that control our vision, is the second branch of the cranial nerves. Optic canal eyes, of course, will be affected by light stimulation, the transmitted signal. When the sun enters the eye, optic nerve excited, electric nerve signals transmitted back to the brain, the electrical nerve signals like a train all the way forward along the optic nerve. With the trigeminal nerve to the electric crossing point, the issue may not be able to keep the trigeminal nerve to accept a little. Trigeminal nerve silly received the wrong signals, but also returned the brain. Regardless of the brain signals coming from, see if there is a signal, that is certainly by foreign body to stimulate the nasal mucosa, and drive them out! Thus, the brain directing the chest, lung, oropharynx, nasal cavity all the muscles began to take a deep breath, and then a violent outlet, this is a sneeze.
In this light, watching the sun sneezing or a beautiful mistake.
The experiments confirmed this hypothesis have yet?
Obviously, apart from the occasional sneeze watching the sun make you embarrassed, but neither physical harm nor cause disease, there is no one willing to invest to study it. So, on this little research.
Few but it is not.
The 1960s, a number of statistical studies of the proportion of people have this reflection, according to different groups of people found that about 10-35% of people have this reflex. Moreover, this is somatic dominant inheritance, meaning that there is no genetic relationship with sex, so no matter who his parents are, as long as there is such a reflection of their children of both sexes, there will be half that reflection.
Searching the medical literature database pubmed, this study found a total of 16 papers, most of which is a review, only a handful of independent research.
Because some special industries need to study this. For example, in 1993, published in the journal Military Medicine article on the subject called "sunshine sneeze reflex for fighter pilots risk factors." This great understanding. They repeated what wavelengths of light can cause sneezing test, or what kind of goggles inhibition. It was found that, with wavelength sneeze or not does not matter, only with the change of light intensity related. But with sunglasses help to reduce the occurrence of such a sneeze. So not only fighter pilot with goggles handsome cool oh.
There is a research anesthesiologist do. Imagine, anesthetists do a lumbar puncture, if the patient can not lead to abrupt changes in light suppressed sneeze occurs, but will be a big thing of. They do not recommend changing the light intensity of the operating room, thus avoiding sneeze reflex come.
There is also research neuroscientists think the sun sneeze reflex may provide some clues to explain the physiological EEG signal disturbance caused by diseases such as migraine, epilepsy. University of California, San Francisco School of Louis Ptcek is to do this in a neurologist. His argument is that a lot of time in patients with epilepsy and seizure because of light stimulation, in addition to the majority of patients with migraine also photophobia. Unfortunately, so far, we did not reach any reliable conclusions.
From the perspective of how biological evolution that explains why humans have such reflections exist? And it is dominant?
It was found that light sneeze reflex is not just humans, many animals have keen sense of smell. These animals usually need to rely on well-developed sense of smell for food and avoid predators, so they are very important for the nose. Keep the nose clean or smooth is particularly important. For humans, it may also have evolutionary benefits. Light reflection occurs when sneezing, and these animals are mainly dogs and cats through the nose sneezing different, humans primarily use the mouth to sneeze, which is why a meal when a sneeze will be very embarrassing. Baby breathe mainly through the nose. Neonatal no way to blow your nose like adults like to exclude foreign body or nasal mucus, so the best and most natural way is to sneeze, which is usually done by a light sneeze reflex sunlight formed. Therefore, although the car suddenly out of the tunnel, if this time a sneeze, maybe cause an accident, but for humans, maybe just evolutionary process left little residue.
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