高级听力 Unit 11 Part 4

谈及是什么致使人们困乏和清醒，并指出目前青少年严重缺少睡眠，如果不加以重视，会造成可怕的后果。

Sleepy Teenagers

M: Teenagers, when allowed to, sleep nearly nine and a half hours every night, as much as young children. But unlike young children, even when teens do get their full sleep, they still have waves of sleepiness in the daytime, and then surges of energy in the evening, making them wide awake late at night. But not for the reasons most of us assume.

F: We kind of always thought that adolescents stayed up late because they liked to, and because there are plenty of things to do.

M: But there's also a big push from biology that makes teenagers such night owls. It comes from that mighty sleep hormone, melatonin.

F: Melatonin is a wonderfully simple signal that turns on in the evening, you’re getting sleepy, and it turns off in the morning.

M: And you awaken. During adolescence, melatonin isn’t secreted until around 11:00 P.M., several hours later than it is in childhood. So the typical teenager doesn’t even get sleepy until that melatonin surge signals the brain that it’s night, no matter how early the teen goes to bed. And the melatonin doesn’t shut off until 7:30. The result is all too evident. A teenager’s body may be in the classroom, but his brain is still asleep on the pillow.

F: One student says: I’ll wake up and I’ll just feel miserable.

M: An adolescent, and particularly the adolescent in high school, is almost bound to get severely sleep deprived.

F: I know as scientist, that’s William Dement of Stanford University. Bill Dement is Dr. Sleep, captivated by the mysteries of sleep for decades, creating the speciality of sleep medicine.

M: He’s been accepting every invitation that he gets to speak to high school students. So he goes to high school and it’ll be 10:30 in the morning, or 2:00 in the afternoon, whenever it is, several hundred students in an auditorium, and he’ll just watch them, as he’s talking.

F: Doing a little spontaneous field research.

M: And after ten minutes of sitting, particularly if the lights are dim, almost without exception, they are all struggling to stay awake. Ten minutes!

……

点击下载全文