Book 1 Reading and Speaking (1108795), страница 3
Текст из файла (страница 3)
In 2005 a fraternity hazing at California State University, Chico, left a 21-year-old mandead after he was forced to drink excessive amounts of water between rounds of push-ups in a cold basement.Club-goers taking MDMA ("ecstasy") have died after consuming copious amounts of water trying to rehydratefollowing long nights of dancing and sweating. Going overboard in attempts to rehydrate is also common amongendurance athletes.
A 2005 study in the New England Journal of Medicine found that close to one sixth ofmarathon runners develop some degree of hyponatremia, or dilution of the blood caused by drinking too muchwater.Hyponatremia, a word cobbled together from Latin and Greek roots, translates as "insufficient salt in theblood." Quantitatively speaking, it means having a blood sodium concentration below 135 millimoles per liter, orapproximately 0.4 ounces per gallon, the normal concentration lying somewhere between 135 and 145 millimolesper liter.
Severe cases of hyponatremia can lead to water intoxication, an illness whose symptoms includeheadache, fatigue, nausea, vomiting, frequent urination and mental disorientation.In humans the kidneys control the amount of water, salts and other solutes leaving the body by sieving bloodthrough their millions of twisted tubules. When a person drinks too much water in a short period of time, the kidneyscannot flush it out fast enough and the blood becomes waterlogged. Drawn to regions where the concentration ofsalt and other dissolved substances is higher, excess water leaves the blood and ultimately enters the cells, whichswell like balloons to accommodate it.Most cells have room to stretch because they are embedded in flexible tissues such as fat and muscle, butthis is not the case for neurons.
Brain cells are tightly packaged inside a rigid boney cage, the skull, and they haveto share this space with blood and cerebrospinal fluid, explains Wolfgang Liedtke, a clinical neuroscientist at DukeUniversity Medical Center. "Inside the skull there is almost zero room to expand and swell," he says. Thus, brainedema, or swelling, can be disastrous.
"Rapid and severe hyponatremia causes entry of water into brain cellsleading to brain swelling, which manifests as seizures, coma, respiratory arrest, brain stem herniation and death,"explains M. Amin Arnaout, chief of nephrology at Massachusetts General Hospital and Harvard Medical School.Where did people get the idea that guzzling enormous quantities of water is healthful? A few years agoHeinz Valtin, a kidney specialist from Dartmouth Medical School, decided to determine if the common advice todrink eight, eight-ounce glasses of water per day could hold up to scientific scrutiny.
After scouring the peerreviewed literature, Valtin concluded that no scientific studies support the "eight x eight" dictum (for healthy adultsliving in temperate climates and doing mild exercise). In fact, drinking this much or more "could be harmful, both inprecipitating potentially dangerous hyponatremia and exposure to pollutants, and also in making many people feelguilty for not drinking enough," he wrote in his 2002 review for the American Journal of Physiology—Regulatory,Integrative and Comparative Physiology.
And since he published his findings, Valtin says, "not a single scientificreport published in a peer-reviewed publication has proven the contrary."Most cases of water poisoning do not result from simply drinking too much water, says Joseph Verbalis,chairman of medicine at Georgetown University Medical Center. It is usually a combination of excessive fluid intakeand increased secretion of vasopressin (also called antidiuretic hormone), he explains. Produced by thehypothalamus and secreted into the bloodstream by the posterior pituitary gland, vasopressin instructs the kidneysto conserve water.
Its secretion increases in periods of physical stress—during a marathon, for example—and maycause the body to conserve water even if a person is drinking excessive quantities.Every hour, a healthy kidney at rest can excrete 800 to 1,000 milliliters, or 0.21 to 0.26 gallon, of water andtherefore a person can drink water at a rate of 800 to 1,000 milliliters per hour without experiencing a net gain inwater, Verbalis explains. If that same person is running a marathon, however, the stress of the situation willincrease vasopressin levels, reducing the kidney's excretion capacity to as low as 100 milliliters per hour.
Drinking800 to 1,000 milliliters of water per hour under these conditions can potentially lead to a net gain in water, evenwith considerable sweating, he says.While exercising, "you should balance what you're drinking with what you're sweating," and that includessports drinks, which can also cause hyponatremia when consumed in excess, Verbalis advises. "If you're sweating500 milliliters per hour, that is what you should be drinking." But measuring sweat output is not easy.
How can amarathon runner, or any person, determine how much water to consume? As long as you are healthy andequipped with a thirst barometer unimpaired by old age or mind-altering drugs, follow Verbalis's advice, "drink toyour thirst. It's the best indicator." (From Scientific American Online, June 21, 2007)Exercise 6. Are the following statements true or false, according to the text? Why? Explain your choice.1. Water is the basic substance in the human organism.2. Drinking excessive amounts of water can lead to death.3. Hyponatremia is a Latin word which means “water overdose”.4.
Hyponatremia is a serious disorder characteristic for sportsmen.105.6.7.8.9.Liver filters water and plays the key role in excreting wastes.Excessive amounts of water are particularly damaging for the brain.A considerable body of evidence confirms the advice to drink much.Excessive water intake combined with physical exercise may result in serious health problems.It’s not recommended to drink while exercising.Exercise 7. These sentences all give very good advice, but they have been divided into separate halves.Match the half-sentences in Column A with the half-sentences in Column B to make 14 sentences whichare correct, complete and true.Write five other pieces of advice for healthy life.A1. Regular exercise is ...2.
A balanced diet should ...3. Medicines should ...4. A patient in shock should ...5. Not taking any exercise is ...6. Reading in bad light can ...7. You should do ...8. A normal adult should drink ...9. HIV can be transmitted ...10. Bad posture can ...11. People with fair complexions ...12. Surgical instruments must ...13.
Babies should ...14. Hemorrhage control routinely should ...Вa) ... burn easily in the sun.b) ... cause back pain.c) ... be inoculated against diphtheria.d) ... be kept out of the reach of children.e) ... be kept warm and lying down.f) ... about 2.5 litres of fluid each day.g) ... good for the heart.h) ... five minutes' exercise every morning.i) ... be sterilised before use.j) ... make the eyes ache.k) ... provide all the nutrients needed, in the correct proportions.l) ...
an unhealthy way of living.m) ... be by pressure and elevation.n) ... by using non-sterile needlesExercise 8. Summarize everything you now know about significance and effects of water into one report.11Unit 3. FungiEvery man carries a parasite somewhere.Japanese proverbExercise 1. What do you know about fungi?1.
What is a fungus? Why are fungi classified into a separate Kingdom?2. Are fungi unicellular or multicellular organisms?3. Are fungi stationary or moving organisms?4. What is the difference between a fungus and a mushroom? Do all fungi have a fruiting body?5.
Are fungi hetero- or autotrophs?6. What ecological functions are performed by fungi?7. What cases of symbiotic relationship between fungi and other organisms do you know? Give examples ofmutualism and parasitism.8. What is the significance of fungi for humans?Exercise 2. Explain the following terms in English:chitinextracellular digestionyeastsaprophytemoldmutualisthypha (hyphae)parasitemyceliumhaustoriaasexual reproductionsexual reproductionsporefragmentationbuddingExercise 3.
Can you believe that fungi are the largest and fastest organisms on Earth? Why? Why not?Read the following two texts (Text A and Text B) to find out.Text A. The Largest Organism on Earth Is a FungusThe blue whale is big, but nowhere near as huge as a sprawling fungus in eastern OregonBy Anne CasselmanNext time you purchase white button mushrooms at the grocery store, just remember, they may be cute andbite-size but they have a relative out west that occupies some 2,384 acres (965 hectares) of soil in Oregon's BlueMountains. Put another way, this humongous fungus would cover 1,665 football fields, or nearly four square miles(10 square kilometers) of turf. The discovery of this giant Armillaria ostoyae in 1998 heralded a new record holderfor the title of the world's largest known organism, believed by most to be the 110-foot- (33.5-meter-) long, 200-tonblue whale.
Based on its current growth rate, the fungus is estimated to be 2,400 years old but could be as ancientas 8,650 years, which would earn it a place among the oldest living organisms as well.A team of forestry scientists discovered the giant after setting out to map the population of this pathogenicfungus in eastern Oregon. The team paired fungal samples in petri dishes to see if they fused, a sign that they werefrom the same genetic individual, and used DNA fingerprinting to determine where one individual fungus ended.This one, A.
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