大学英语综合教程 学生用书 U07_tA

[00:00.00]The Brain
[00:03.29]The brain is the most complicated  part of the human body,
[00:09.85]and yet less is known about it than any other part.
[00:15.60]It is quite small(a normal hunman brain weighs about one kilogram),
[00:22.65]and a bigger brain does not mean a better brain.
[00:28.60]The surface area of the cortex(the outside part)
[00:34.46]is more important than the actual size of the brain.
[00:40.62]Over the centuries,the cortex has grown,
[00:45.87]and it is now deeply folded in order to provide a larger surface
[00:53.21]area without requiring a greater total volume.
[00:59.48]The brain receives information
[01:04.13]from the outside world through the Sensory System.
[01:09.88]This information is gathered through the eyes,
[01:15.62]the nose,the ears,the mouth and the surface of the body.
[01:22.00]It is then stored in the memory which has a tremendous capacity.
[01:28.95]In fact,scientists do not fully understand how the memory works
[01:37.10]but they have not shown that there is any limit
[01:42.03]to the amount of information that the human brain can store.
[01:48.67]Also,it appears that the information is never lost.
[01:55.02]Very old people often remember incidents from their childhood
[02:02.25]which have not come to their minds for sixty to seventy years.
[02:08.52]If we have stored something in our memory,it is there.
[02:14.87]But can we get it out again to use it?
[02:20.12]That is the difficulty.
[02:24.38]Some of the information we receive only goes into the Short Term Memory;
[02:32.82]We only keep this information for a minute or two,then we lose it.
[02:41.28]Schoolchildren in class often seem to use only the Short Term Memory
[02:49.04]if they are not interested in the subject.
[02:54.29]Shoolteahcers have a description for this,
[03:00.04]saying that things go"in one ear and out the other".
[03:06.59]But if a child is interested,
[03:11.24]he puts the information in his Long Term Memory,and he never loses it
[03:18.50](though,of course,there are times when he cannot recall it).
[03:25.17]The brain sends instructions to the body through the Motor System.
[03:32.61]This tells the arms and the legs to move,
[03:38.07]the eyes to focus,the hands to open and close,
[03:44.42]the jaw to move up and down,etc.
[03:49.46]Through the Motor system
[03:53.30]we can even control our breathing for a short time.but not for long.
[04:00.04]It is very difficult,however,to make the body do something that is bad for it.
[04:07.88]Try to cut yourself with a knife,nor burn yourself with a match,
[04:15.03]and you will find it is very difficult to do.
[04:20.18]There is a third system which the brain controls,
[04:25.53]but not consciously;this is called the Homeostatic System.
[04:31.80]Through this system the brain tells the heart how fast to beat,
[04:38.44]it tells digestive system how much food to absorb,
[04:44.81]and it tells the glands in the body when to sweet,salivate,etc.
[04:52.36]This we cannot normally control,though some fakirs,
[04:58.50]or Hindu mystics,in the East have claimed that
[05:03.75]they can control parts of the Homeostatic System.
[05:09.99]So the brain is a complex and delicate part of the human organism,
[05:17.44]and in addition to the three systems that have been mentioned,
[05:23.60]the brain is able to work in special ways.
[05:29.04]It can use the information that is stored in it to think creatively,
[05:35.99]allowing the human race to make astonishing scientific,
[05:42.23]artistic and technical progress.
[05:47.09]It will be a long time before a computer is invented
[05:52.94]that can do this because imagination is a very difficult thing
[05:59.89]to build into integrated circuits and silicon ships.