BR__The Body Bill Bryson P. 2 Flashcards
Card one: P262:
Extraordinarily, some birds and marine mammals are able to switch off one half of their brain at a time, so that one half remains alert while the other is snoozing.
Newborn babies spend at least 50 percent of their sleep time (which is most of their time anyway) in the REM phase. For fetuses it may be as much as 80 percent.
Most men have erections during REM sleep. Women likewise experience increased blood flow to the genitals. No one knows why, but it seems not to be overtly associated with erotic impulses. Typically, a man will be erect for two hours or so a night. We are more restless at night than most of us realize. The average person turns over or significantly changes position between thirty and forty times in the course of a night. We also wake up far more than you might think. Arousals and brief awakenings in the night can add up to thirty minutes without being noticed.
As well as normal overnight sleep, we also commonly indulge in snatches of wakeful-hours sleep in a state known as hypnagogia, a netherworld between waking and unconsciousness, often without being aware of it. Alarmingly, when a dozen airline pilots on long-haul flights were studied by sleep scientists, almost all were found to have been asleep, or all but asleep, at various times during the flight without realizing it.
“What’s really interesting about these third receptors,” Foster told me when we met in his office at Brasenose College, just off the High Street, “is that they function completely independently of sight. As an experiment, we asked a lady who was completely blind—she had lost her rods and cones as a result of a genetic disease—to tell us when she thought the lights in the room were switched on or off. She told us not to be ridiculous because she couldn’t see anything, but we asked her to try anyway. It turned out she was right every time. Even though she had no vision—no way of ‘seeing’ the light—her brain detected it with perfect fidelity at a subliminal level. She was astonished. We all were.”
How exactly melatonin relates to sleep is still not understood. Melatonin levels within us rise as evening falls and peak in the middle of the night, so it would seem logical to associate them with drowsiness, but in fact melatonin production also rises at night in nocturnal animals when they are most active, so it is not promoting sleepiness.
The pressure to sleep grows more intense the longer we stay awake. This is in large part a consequence of an accumulation of chemicals in the brain as the day goes by, in particular one called adenosine, which is a by-product of the output of ATP (or adenosine triphosphate), the little molecule of intense energy that powers our cells. The more adenosine you accumulate, the drowsier you feel.
Between 10 and 20 percent of adults in the world suffer from insomnia, according to various studies.
About 50 percent of people who snore have some degree of sleep apnea.
That said, men and women unquestionably are very unalike in many important ways. Women (and we are talking here about healthy, fit women) carry about 50 percent more fat on their frames than fit, healthy men. This not only makes the woman more agreeably soft and shapely to suitors but also gives her reserves of fat she can call upon for milk production during times of hardship. Women’s bones wear out sooner, particularly after menopause, so they suffer more breaks in later life. Women get Alzheimer’s twice as often (partly because they also live longer) and experience higher rates of autoimmune diseases. They metabolize alcohol differently, which means they get intoxicated more easily and succumb to alcohol-related diseases like cirrhosis faster than men do.
Men have their own differences. They get Parkinson’s disease more often and commit suicide more, even though they suffer less from clinical depression.
Women are anatomically different in one other very significant way: they are the sacred keepers of human mitochondria—the vital little powerhouses of our cells. Sperm pass on none of their mitochondria during conception, so all mitochondrial information is transferred from generation to generation through mothers alone. Such a system means that there will be many extinctions along the way. A woman endows all her children with her mitochondria, but only her daughters have the mechanism to pass it onward to future generations. So if a woman has only sons or no children at all—and that happens quite often, of course—her personal mitochondrial line will die with her. All her descendants will still have mitochondria, but it will come from other mothers on other genetic lines. In consequence, the human mitochondrial pool shrinks a little with every generation because of these localized extinctions. Over time, the mitochondrial pool for humans has shrunk so much that, almost unbelievably but rather wonderfully, we are all now descended from a single mitochondrial ancestor—a woman who lived in Africa about 200,000 years ago. You might have heard her referred to as Mitochondrial Eve. She is, in a sense, mother of us all.
The rest of the clitoris plunges into the interior and extends down both sides of the vagina for about five inches.
Chapter 18. IT’S A LITTLE hard to know what to make of sperm. On the one hand, they are heroic: the astronauts of human biology, the only cells designed to leave our bodies and explore other worlds. But on the other hand, they are blundering idiots. Shoot them into a womb and they seem curiously ill-prepared for the one task evolution has given them. They are terrible swimmers and appear to have almost no sense of direction. Unaided, it could take a sperm ten minutes to swim across a space the width of one of the words on this page. That’s why a male orgasm is such a vigorous endeavor. What seems to the man purely a burst of pleasure really is a kind of rocket launch. Once the sperm are expelled, it isn’t known whether they move about randomly until one strikes lucky or whether they are drawn to the waiting egg by some chemical signal.*1 In either case, overwhelmingly they fail. The chances of a successful fertilization from a single randomly timed act of sex have been calculated to be only about 3 percent. And matters seem to be getting worse across the Western world. About one in seven couples now seek help in conceiving.
A twenty-week-old fetus will weigh no more than three or four ounces but will already have 6 million eggs inside her. That number falls to 1 million by the time of birth and continues to fall, though at a slower rate, through life. As she enters her childbearing years, a woman will have about 180,000 eggs primed and ready to go.
by the age of thirty-five a woman’s stock of eggs is 95 percent exhausted and those that remain are more liable to produce faults or surprises, like multiple births. Once women pass thirty, they are much more likely to have twins.
Just since 1980, the age of puberty has fallen in America by eighteen months. About 15 percent of girls now begin puberty by age seven.
Perhaps as many as half of all conceptions are lost without being noticed. Without this, the rate of birth defects would be 12 percent instead of 2 percent.
thalidomide. Read note in book for long story.
In 1847, a medical instructor in Vienna named Ignaz Semmelweis realized that if doctors washed their hands before conducting intimate examinations, the disease all but vanished. “God knows the number of women whom I have consigned prematurely to the grave,” he wrote despairingly when he realized it was all a matter of hygiene. Unfortunately, no one at all listened to him. Semmelweis, who was not the most stable of persons at the best of times, lost his job and then his mind and ended up stalking through the streets of Vienna, ranting at thin air. Eventually, he was confined to an asylum where he was beaten to death by his guards. Streets and hospitals should be named for him, poor man. (What an interesting story.) (nobody would listen to this genius)
The average cost of childbirth in the United States is about $30,000 for a conventional birth and $50,000 for a Cesarean, about three times the cost for either in the Netherlands. Yet American women are 70 percent more likely to die in childbirth than women in Europe and about three times more likely to suffer a pregnancy-related fatality
On P 297, I reached copy limit for this book. Refer to actual book highlights for remainder.
P 387 is last actual reading page of the book.
P326 amazing story about smallpox being super contagious.
we now know, most miscarriages and other setbacks in pregnancy are because of problems with the placenta, not the fetus.
As well as nurturing symbiotic bacteria, breast milk is full of antibodies. There is some evidence that a nursing mother absorbs a little of her suckling baby’s saliva through her breast ducts and that this is analyzed by her immune system, which adjusts the amount and types of antibodies she supplies to the baby, according to its needs. Isn’t life marvelous?
If you want to imagine what a disease might do if it became bad in every possible way, you could do no better than consider the case of smallpox. Smallpox is almost certainly the most devastating disease in the history of humankind. It infected nearly everyone who was exposed to it and killed about 30 percent of victims. The death toll in the twentieth century alone is thought to have been around 500 million. Smallpox’s astounding infectiousness was vividly demonstrated in Germany in 1970 after a youthful tourist developed it upon returning home from a trip to Pakistan. He was placed in hospital quarantine but opened his window one day to sneak a cigarette. This, it has been reported, was enough to infect seventeen others, some two floors away.
She had contracted smallpox via an air duct from a lab one floor below her office. There, a virologist named Henry Bedson had been studying one of the last smallpox samples on Earth still allowed for research. He was frantically working against a deadline before his own stocks were to be destroyed and evidently grew careless in keeping them safe. Poor Janet Parker died about two weeks after being exposed and in so doing became the last person on Earth to be killed by smallpox. She had actually been vaccinated against the disease twelve years earlier, but smallpox vaccine doesn’t last. When Bedson learned that smallpox had escaped from his lab and killed an innocent person, he went out to his garden shed and committed suicide, so in a sense he was smallpox’s last victim. The hospital ward on which Parker was treated was sealed off for five years.
The idea, roughly, is that we are born with the bodies of hunter-gatherers but pass our lives as couch potatoes. If we want to be healthy, we need to eat and move about a little more like our ancient ancestors did. That doesn’t mean we have to eat tubers and hunt wildebeest. It means we should consume a lot less processed and sugary foods and get more exercise. Failure to do that, however, is what is giving us the disorders like type 2 diabetes and cardiovascular disease that are killing us in great numbers.
70 percent of the diseases that kill us could easily be preventable if we would just live more sensibly.
Cancer is actually not one disease, but a suite of more than two hundred with lots of different causes and prognoses. Eighty percent of cancers, known as carcinomas, arise in epithelial cells—that is, the cells that make up the skin and the linings of organs.
Lifestyle is a huge factor in determining which of us get cancer. More than half of cases, by some calculations, are caused by things we can do something about—smoking, drinking to excess, and overeating primarily. The American Cancer Society found a “significant association” between being overweight and incidence of cancer
In the United States alone, 2.4 million fewer people have died of cancer in the last thirty years than would have if the rates had stayed unchanged.
life expectancy on Earth improved by as much in the twentieth century as in the whole of the preceding eight thousand years.
When we read that life expectancy was forty-six years for American men in 1900, that doesn’t mean that most men got to forty-six and then keeled over. Life expectancies were short because so many children died in infancy, and that dragged the average down for everyone. If you got past childhood, the chances of living to a reasonably advanced age weren’t bad.
In 1950, 216 children in every thousand—nearly a quarter—died before the age of five. Today the figure is just 38.9 early childhood deaths in a thousand—one-fifth what it was seventy years ago
. In St. Louis, Missouri, make a twenty-minute drive from prosperous Clayton to the inner-city Jeff-Vander-Lou neighborhood and life expectancy drops by one year for every minute of the journey, a little over two years for every mile.
Americans lead more unhealthy lifestyles than most other people, and that is true at all levels of society. As Allan S. Detsky observed in The New Yorker, “Even wealthy Americans are not isolated from a lifestyle filled with oversized food portions, physical inactivity, and stress.” The average Dutch or Swedish citizen consumes about 20percent fewer calories than the average American, for instance. That doesn’t sound massively excessive, but it adds up to 250,000 calories over the course of a year. You would get a similar boost if you sat down about twice a week and ate an entire cheesecake.
Where America really differs from other countries is in the colossal costs of its health care. An angiogram, a survey by The New York Times found, costs an average of $914 in the United States, $35 in Canada. Insulin costs about six times as much in America as it does in Europe. The average hip replacement costs $40,364 in America, almost six times the cost in Spain, while an MRI scan in the United States is, at $1,121, four times more than in the Netherlands. The entire system is notoriously unwieldy and cost-heavy. America has about 800,000 practicing physicians but needs twice that number of people to administer its payments system. The inescapable conclusion is that higher spending in America doesn’t necessarily result in better medicine, just higher costs.
Many cancers have long sojourn times and progress so slowly that the victims almost always die of something else before the cancer gets them.
Between 20 and 70 percent of men suffer impotence or incontinence after treatments. One in five experience complications from the biopsy alone. Talking prostrate surgery.
for every 1,000 men screened for prostate cancer, about one life was saved—great news for that individual, but not so good for the large numbers of others who may spend the rest of their lives incontinent or impotent, the majority of them having undergone serious but possibly ineffectual treatments.
a quarter of all health-care spending—is wasted on pointless precautionary maneuvers. A similar study in Washington State put the amount of waste even higher, at nearly 50 percent, and concluded that as much as 85 percent of preoperative lab tests are completely unnecessary.
Alzheimer’s disease. Eradicating it altogether, according to the biologist Leonard Hayflick, would add just nineteen days to life expectancy.
nearly half of people aged fifty or more suffer from some chronic pain or disability.
The average person born before 1945 could expect to enjoy only about eight years of retirement
With each cell division, telomeres shorten until eventually they reach a predetermined length (which varies markedly from one cell type to another) and the cell dies or becomes inactive.
As we age, the bladder becomes less elastic and cannot hold as much, which is why one of the curses of aging is being forever on the lookout for a restroom.
After the age of forty, the volume of blood going to the kidneys decreases by an average of 1 percent a year.
Most animals die soon after they cease to be reproductive,
She outlived her husband by more than half a century and her only child, a daughter, by sixty-three years. Calment smoked all her life—at the age of 117, when she finally gave up, she was still smoking two cigarettes a day—and ate two pounds of chocolate every week.
Every day, around the world 160,000 people die. That’s about 60 million fresh bodies a year, roughly equivalent to killing off the populations of Sweden, Norway, Belgium, Austria, and Australia year after year.
Getting old is the surest route to dying. In the Western world, 75percent of deaths from cancer, 90 percent from pneumonia, 90percent from flu, and 80 percent from all causes occur in people sixty-five years of age or older.
decomposition in a sealed coffin takes a long time—between five and forty years, according to one estimate, and that’s only for those who are not embalmed. The average grave is visited for only about fifteen years, so most of us take a lot longer to vanish from the earth than from others’ memories.
reaching 80 is largely a consequence of following a healthy lifestyle, but after that it is almost entirely a matter of genes.
It is an extraordinary fact that having good and loving relationships physically alters your DNA. Conversely, a 2010 U.S. study found, not having such relationships doubles your risk of dying from any cause.
Alzheimer’s accounts for between 60 and 70 percent of all dementia cases and is thought to affect some fifty million people around the world, but Alzheimer’s is only one of about a hundred types of dementias,
