问题 多项选择题 X型题

抑制胃排空的主要因素是()

A.大量食物入胃的机械和化学刺激

B.十二指肠内的酸性刺激

C.十二指肠内的脂肪增加

D.十二指肠内渗透压增高

E.食糜进入十二指肠的机械和化学刺激

答案

参考答案:B, C, D, E

解析:胃内因素促进排空:胃内容物的量和排空速度呈线性关系。迷走一迷走反射与壁内神经丛反射可使胃运动增加,加快排空;排空常受情绪的影响,在激动、兴奋时加快,在忧虑、悲伤及疼痛时排空减慢;蛋白质产物,可促进促胃液素释放,促胃液素可以加强胃体和胃窦收缩,但由于它同时也增强幽门括约肌的收缩,所以其作用不是促进而是延缓排空。十二指肠内因素抑制排空:盐酸、脂肪、高渗溶液、蛋白消化产物、机械性扩张刺激,通过肠-胃反射和刺激小肠上段黏膜释放缩胆囊素、促胃液素、促胰液素、抑胃肽等,可抑制排空,进入十二指肠的盐酸被中和、消化产物被吸收,抑制胃排空因素被消除后,胃运动又增强,因此,胃排空表现为间断性。

阅读理解

阅读理解。

     We can see how the product life cycle works by looking at the introduction of instant coffee. When it

was introduced, most people did not like it as well as "regular" coffee, and it took several years to gain general

acceptance (introduction stage). At one point, though, instant coffee grew rapidly in popularity, and many

brands were introduced (stage of rapid growth). After a while, people became attached to one brand and

sales leveled off (stage of maturity). Sales went into a slight decline when freeze-dried coffees were

introduced (stage of decline).

     The importance of the product life cycle to marketers is this: Different stages in the product life cycle

call for different strategies. The goal is to extend product life so that sales and profits do not decline. One

strategy is called market modification. It means that marketing managers look for new users and market

sections. Did you know, for example, that the backpacks that so many students carry today were originally

designed for the military?

     Market modification also means searching for increased usage among present customers or going for a

different market, such as senior citizens. A marketer may re-position the product to appeal to new market

sections.

     Another product extension strategy is called product modification. It involves changing product quality,

features, or style to attract new users or more usage from present users. American auto manufacturers are

using quality improvement as one way to recapture world markets. Note, also, how auto manufacturers once

changed styles dramatically from year to year to keep demand from falling.

1. According to the passage, when people grow fond of one particular brand of a product, its sales will _____.

A. decrease gradually

B. remain at the same level

C. become unstable

D. improve enormously

2. Marketers need to know which of the four stages a product is in so as to _____.  

A. work out marketing policies

B. promote its production  

C. increase its popularity

D. speed up its life cycle

3. The author mentions the example of "backpacks" in paragraph two to show the importance of _____.

A. pleasing the young as well as the old

B. increasing usage among students

C. exploring new market sections

D. serving both military and civil needs

4. In order to recover their share of the world market, U.S. auto makers are _____.

A. improving product quality

B. increasing product features

C. modernizing product style

D. re-positioning their product in the market

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