论文部分内容阅读
大脑是人体代谢最活跃的器官。大脑的重量只占体重的四十七分之一,而它需要的氧气的量约占全身用氧量的四分之一,在人体各部位当中占首位。另外,大脑组织所需要的糖比其它器官要多得多,大脑所需要的大量氧气和糖,都是靠血液来输送的。大脑的血流量大约相当于心脏总排出量的五分之一,可见要维持大脑的活动,心脏和血液循环的负担是很大的。科学家做过这样一个实验:让一个人平躺在一个大天平上,然后让他做一道复杂的数学题,随着思考的不断深入,人们可以见到天平上人的头部所在的一侧逐渐下沉。这表明血液对大脑的工作有直接影响。人们在进行脑力劳动的时候,一般是静坐姿势,这时候神经组织中的化学成份在逐渐起变化,新陈代谢的废物逐渐增多。而人体的其它器官、如消化、呼吸、循环等系统都由于人体的相对静止,其机能状态跟不上大脑紧张活动的需要,
The brain is the body’s most active organ metabolism. The brain weighs only one-fourth of the body weight, and the amount of oxygen it needs is about a quarter of the body’s oxygen use, making up the top of every part of the body. In addition, the brain needs more sugar than any other organ, and the bulk of the brain’s oxygen and sugar are delivered by the bloodstream. The brain’s blood flow is roughly equivalent to one-fifth of the total cardiac output, showing that the burden of maintaining the brain’s activity, heart and blood circulation is substantial. Scientists have done such an experiment: a person lying on a large balance, and then let him do a complex math problems, with the deepening of thinking, people can see the balance on the side of the human head gradually sink. This shows that the blood has a direct effect on the work of the brain. People in mental work, usually sitting position, this time the chemical composition of nerve tissue is gradually changing, the gradual increase in metabolic waste. The body’s other organs, such as digestion, breathing, circulation and other systems are due to the body’s relative rest, its functional status can not keep up with the needs of brain activity,