问题 单项选择题 A1型题

高血压患者较正常人明显增高的心泵功能指标是()

A.心输出量

B.射血分数

C.心指数

D.心脏做功量

E.以上均正确

答案

参考答案:D

解析:动脉血压增高,就意味着心脏的后负荷增加,后负荷增加,即心室射血遇到的动脉阻力增大,等容收缩期室内压峰值必然也增高,左室射血速度减慢,致使每搏输出量减少,结果使心室剩余血量增加,使充盈体积增加,继发地启动Starling心脏调节机制,每搏输出量又可恢复正常水平,其做功量也增大。

单项选择题
单项选择题

D

American cities are similar to other cities around the world: In every country, cities reflect the values of the culture. American cities are changing, just as American society is changing.

After World War U , the population of most large American cities decreased ; however, the population in many Sun Belt cities increased. Los Angeles and Houston are cities where population shifts(转移) to and from the city reflect the changing values of American society. In the late 1940s and early 1950s, city residents (居民) became wealthier. They had more children so they needed more space. They moved out of their apartments in the city to buy their own homes. They bought houses in the suburbs (郊区).

Now things are changing. The children of the people who left the cities in the 1950s are now adults. Many, unlike their parents, want to live in the cities. They continue to move to Sun Belt cities and older ones of the Northeast and Midwest. Many young professionals are moving back into cities. They prefer the cities to the suburbs because their jobs are there; or they just enjoy the excitement and possibilities that the city offers.

This population shift is bringing problems as well as benefits. Countless poor people must leave their apartments in the city because the owners want to sell the buildings or make apartments for sale instead of renting, In the 1950s, many poor people did not have enough money to move to the suburbs; now many of these same people do not have enough money to stay in the cities.

Only a few years ago, people though that the older American cities were dying. Some city residents now see a bright, new future. Others see only problems and conflicts. One thing is sure: many dying cities are alive again.

We can conclude from the text that().

A. American cities are changing far the worse

B. people have different views on American cities

C. many people are now moving from American cities

D. the population is decreasing in older American cities