Can you read in the car? If so, consider yourself pretty lucky. For one-third of the population, looking at a book while moving along in a car or a boat or train or plane quickly makes them sick to their stomach. But why do we get motion sickness in the first place? Well, believe it or not, scientists aren't exactly sure. The most common theory has to do with mismatched sensory signals. When you travel in a car, your body gets two different messages. Your eyes are seeing the inside of a vehicle, which doesn't seem to be moving. Meanwhile, your ear is telling your brain you're accelerating. Wait, your ear? Your ear has another important function besides hearing. In its innermost part lies a group of structures known as the vestibular system, which gives us our sense of balance and movement. Inside there are three semicircular tubules that can sense rotation, one for each dimension of space. And there are also two hair-lined sacks filled with fluid. When you move, the fluid shifts and tickles the hairs, telling your brain if you're moving horizontally or vertically. All this tells your body which direction you're moving in, how much you've accelerated, even at what angle. In a car, your vestibular system correctly senses your movement, but your eyes don't see it, especially when glued to a book. The opposite can happen. You're at the movies, and the camera makes a sweeping move. This time, your eyes think you're moving while your ear knows you're sitting still. But why does this conflicting information make us feel so terrible? Scientists aren't sure, but they think there's an evolutionary explanation. Fast moving vehicles and video recordings have only existed in the last couple of centuries, a blink in evolutionary time. For most of our history, there wasn't that much that could cause this sensory mix-up, except for poisons. And because poisons are not the best thing for survival, our bodies evolved a direct but unpleasant way to get rid of what we ate that was causing the confusion. It's a pretty reasonable theory, but it leaves things unexplained, like why women are more affected by motion sickness than men, or why passengers get more nauseous than drivers. Another theory suggests that the cause is more about the way some unfamiliar situations make it harder to maintain our natural body posture. Studies show that being immersed in water or just changing your stance can greatly reduce the effects of motion sickness. But we don't really know what's going on. We know the more common remedies for car queasiness -- looking at the horizon, over-the-counter pills, chewing gum, but none are totally reliable nor can they handle intense motion sickness and sometimes the stakes are far higher than just not being bored during a long car ride. At NASA, where astronauts are hurled into space at 17,000 miles per hour, motion sickness is a serious problem. In addition to researching the latest space-age technologies, NASA also spends a lot of time figuring out how to keep astronauts from vomiting up their space rations. Like understanding the mysteries of sleep or curing the common cold, motion sickness is one of those seemingly simple problems that, despite amazing scientific progress, we still know very little about. Perhaps one day the exact cause of motion sickness will be found, and with it, a completely effective way to prevent it, but that day is still on the horizon.
Možete li da čitate u kolima? Ako možete, smatrajte se prilično srećnim. Otprilike trećini populacije, čitanje u vožnji automobilom, čamcem, vozom, ili avionom uzrokuje i mučninu u želucu. Ali zašto uopšte imamo mučninu? Pa, verovali ili ne, ni naučnici nisu potpuno sigurni. Najčešća teorija ima veze sa neusklađenim čulnim signalima. Kada putujete automobilom, vaše telo dobija dve vrlo različite poruke. Vaše oči vide unutrašnjost vozila, koja deluje nepomično, dok vaše uši govore mozgu da se krećete. Stanite malo, vaše uši? Da, vaše uši u stvari imaju još jednu važnu funkciju osim slušanja. U dubokoj unutrašnjosti uha nalazi se centar za ravnotežu, koji nam daje osećaj ravnoteže i kretanja. Unutar njega postoje tri polukružne cevčice koje osećaju rotaciju, po jedna za svaku dimenziju u prostoru. Tu su i dve vrećice oivičene dlačicama, ispunjene tečnošću. Kada se krećete, tečnost se premešta i golica dlačice, koje govore mozgu da li se krećete horizontalno ili vertikalno. Sa svim tim u kombinaciji vaše telo oseća u kom pravcu se krećete, koliko ubrzavate, pa čak i pod kojim uglom. Kada ste u kolima, vaš centar za ravnotežu ispravno oseća pokret, ali vaše oči ga ne registruju, naročito ako su prikovane za knjigu. I suprotno se može desiti. Recimo kada ste u bioskopu, a kamera napravi širok, brišući pokret. Ovog puta vaše oči misle da se krećete dok uši znaju da sedite mirno. Zašto ove suprotstavljene informacije čine da se osećamo tako loše? Naučnici takođe nisu sigurni, ali smatraju da je objašnjenje u evoluciji. Kao što znate, brza vozila i video zapisi postoje poslednjih nekoliko vekova, jedva treptaj u evolutivnom periodu. U najvećem delu istorije nije postojalo toliko toga što može dovesti do suprotstavljenih signala osim otrova. I iz razloga što otrovi nisu najbolja stvar za opstanak naše telo je razvilo prilično jasan ali ne i veoma prijatan način da se reši svega što smo pojeli, a može nam izazvati smetnje. Ova teorija čini se razumnom, ali ostavlja dosta neobjašnjenog na primer: zašto je ženama češće muka nego muškarcima, ili usled čega su putnici time pogođeniji nego vozači. Još jedna teorija kaže da uzrok možda više ima veze sa nepoznatim situacijama koje nam otežavaju prirodan stav tela. Istraživanja pokazuju da zaronom u vodu ili menjanjem položaja tela u mnogome možemo smanjiti efekat mučnine pri kretanju. Ali ipak, ne znamo šta se stvarno dešava. Znamo standardna sredstva koja pomažu kod mučnine pri kretanju - gledanje u horizont, žvakanje žvake, tablete za mučninu - iako ništa nije potpuno pouzdano niti može izlečiti jako intenzivne mučnine pri putovanjima, a nekad je rizik daleko veći od dosađivanja pri dugom putovanju autom. U NASI, gde se astronauti šalju u svemir pri brzini od oko 27.000 km / h, mučnina pri kretanju je ozbiljan problem. Te, pored istraživanja poslednje svemirske tehnologije, NASA provodi i dosta vremena u pokušaju da ustanovi kako da spreči astronaute da ispovraćaju marljivo pripremljene zalihe hrane. Slično razumevanju tajni sna ili lečenju uobičajene prehlade, mučnina u vožnji ostaje jedan od onih naizgled jednostavnih problema, o kom, uprkos neverovatnom naučnom napretku, još uvek znamo vrlo malo. Možda će jednog dana tačan uzrok mučnine pri kretanju, a ujedno i potpuno delotvoran način preventive, biti poznati, ali za sada taj dan je samo na horizontu.