【正文】 ponse to activation of this nerve supply, smooth muscle contracts (notably in the gut), the frequency of heart beat is slowed, and glands secrete. Acetylcholine is also an important transmitter at many sites in the brain at nervetonerve synapses. To understand how acetylcholine brings about a variety of effects in different cells it is necessary to understand membrane receptors. In postsynaptic membranes (those of the cells on which the nerve fibres terminate) there are many different sorts of receptors and some are receptors for acetylcholine. These are protein molecules that react specifically with acetylcholine in a reversible fashion. It is the plex of receptor bined with acetylcholine which brings about a biophysical reaction, resulting in the response from the receptive cell. Two major types of acetylcholine receptors exist in the membranes of cells. The type in skeletal muscle is known as ‘nicotinic’。t get sick pay when I am ill. But I can work extra hours. I often do overtime at the weekend if the restaurant is busy. At Christmas the boss gives us extra money—a bonus. 1. How often do temporary employees get their pay? Every week. 2. ―Tip‖ is closest in meaning (意義 ) to __ money for good service _. 3． What does the writer do? He serves customers in a restaurant 4. The writer __ often works on Saturdays and Sundays __ 5. The writer doesn’t have enough money to __ see his parents in Italy ___ 短文 四 2 In schools all over the world, boys and girls are learning foreign languages. Everyone knows his own language, but another one is very useful especially(尤其 ) when you travel to other countries. If you go to France, you should be able to speak French, and in Germany, people will expect you to understand German. How many languages are there in the world? There are about fifty hundred, but a lot of them are not very important. English is one of the most important because so many people use it, not only in England and America but also in other parts of the world. About 200,000,000 people speak it as a second language. It is difficult to say how many people are learning it. Many millions of schoolboys and schoolgirls are trying to do so. 3 learning foreign languages is very useful. Right 3 There are about 1,5oo languages in the world Wrong 3 A lot of languages in the world are very important . Wrong 3 People in Brazil(巴西 )also apeak English . Dosen’t say. 35 、 About 200,000,000 people are learning English , Wrong 4 請(qǐng)您刪除一下內(nèi)容， O(∩ _∩ )O謝謝?。?！ 2021年中央電大期末復(fù)習(xí)考試小抄大全，電大期末考試必備小抄，電大考試必過(guò)小抄Acetylcholine is a neurotransmitter released from nerve endings (terminals) in both the peripheral and the central nervous systems. It is synthesized within the nerve terminal from choline, taken up from the tissue fluid into the nerve ending by a specialized transport mechanism. The enzyme necessary for this synthesis is formed in the nerve cell body and passes down the axon to its end, carried in the axoplasmic flow, the slow movement of intracellular substance (cytoplasm). Acetylcholine is stored in the nerve terminal, sequestered in small vesicles awaiting release. When a nerve action potential reaches and invades the nerve terminal, a shower of acetylcholine vesicles is released into the junction (synapse) between the nerve terminal and the ‘effector’ cell which the nerve activates. This may be another nerve cell or a muscle or gland cell. Thus electrical signals are converted to chemical signals, allowing messages to be passed between nerve cells or between nerve cells and nonnerve cells. This process is termed ‘chemical neurotransmission’ and was first demonstrated, for nerves to the heart, by the German pharmacologist Loewi in 1921. Chemical transmission involving acetylcholine is known as ‘cholinergic’. Acetylcholine acts as a transmitter between motor nerves and the fibres of skeletal muscle at all neuromuscular junctions. At this type of synapse, the nerve terminal is closely apposed to the cell membrane of a muscle fibre at the socalled motor end plate. On release, acetylcholine acts almost instantly, to cause a sequence of chemical and physical events (starting with depolarization of the motor endplate) which cause contraction of the muscle fibre. This is exactly what is required for voluntary muscles in which a rapid response to a mand is required. The action of acetylcholine is terminated rapidly, in around 10 milliseconds。t get holiday pay. It39。t work. I want to go to Italy to see my parents. But I haven39。6 an hour, and I don39。 復(fù)習(xí)自測(cè)題（ 3） —— 閱讀理解 一、閱讀下列短文，從 A、 B、 C三個(gè)選項(xiàng)中選出一個(gè)正確答案。 3. How about playing football tomorrow afternoon? 明天下午去踢球怎么樣？ 4. The bank is on the corner. It’s opposite the newsagent. 銀行在拐角處，在報(bào)攤的對(duì)面。 交際用語(yǔ) 1. What do your parents do? My father is a manager. My mother is a murse. 2. Can I help you? — Yes, I’d like some apples, please. 3. Hello, Linda, how are you? Very well, thank you . Are you good. 4. What does her boyfriend look like? —He is quite tall with fair curly hair. 5. Could you ring them up please? I’m sometimes quite nervous on the phone. —Yes, of course. I will phone them for you. 詞匯與結(jié)構(gòu) 1. I’m a deputy manager. I work about an IT pany. 2. What is your job? —I’m an accountant. 3. Who is that man over there? Do you know his name? 4. This is his bock. Could you give it to him? 5. How much yine do you need for the party? 6. Would you like a drink? Wine? Beer? 7. How do I get to the gym? 8. I’d like to invite you to a party this Saturday. 9. I like documentaries on TV. So do I. 10. The Business Banking Department is on the second floor. 11. The shop closes at six every day. 12. He is a good student. He always es early. 13. What’s wrong with your clock? 14. Pandas and m