简述神经-肌肉接头处兴奋的传递过程。
动作电位沿运动神经传导,神经末梢外膜上发生去极化,引起该处电压依赖式门控式Ca2+通道开放,细胞外Ca2+内流,(1分)轴突小体内Ca2+浓度升高,促使囊泡前移,与前膜融合、破裂、释放Ach。(1分)Ach经接头间隙与终板膜上的N2受体结合,(1分)使终板膜对Na+、K+和少量Ca++透性增大,引起Na+内流、K+外流,尤其是Na+内流,在终板膜上产生去极化电紧张电位。即终板膜电位。(1分)终板膜电位总和达到阈电位水平,在终板膜上爆发动作电位。(1分)
暂无解析
不能满足过分的自我要求,有强烈不满感,对比自己嫉妒成功的竞争者,性格谨小慎微、拘泥细节、至善主义和雄心勃勃,不能达到时便导致自我惩罚。这是下述哪种疾病的心理特征()
Importance of Education
汉译英:茶 花(camellia)的自然花期在 12 月至翌年 4 月,以红色系为主,另有黄色系和白色系等,花色艳丽。本届花展充分展示了茶花的品种资源和科研水平,是近三年来本市规模最大的一届茶花展。为了使广大植物爱好者有更多与茶花亲密接触的机会,本届茶花展的布展范围延伸至整个园区,为赏花游客带来便利。此次茶花展历时2个月,展期内 200 多个茶花品种将陆续亮相。
At each of its 20 buildings at its 200-acre campus in Raleigh, North Carolina, SAS Institute provides coffee break rooms stocked with free soda, fresh fruit, M&Ms and pastries.
California is a land of variety and contrast. Almost every type of physical land feature , sort of arctic ice fields and tropical jungles can be found within its borders. Sharply contrasting types of land often lie very close to one another. People living in Bakersfield , for instance,can visit the Pacific Ocean and the coastal plain , the fertile San Joaquin Valley , the arid Mojave Desert , and the high Sierra Nevada, all within a radius of about 100 miles. In other areas it is possible to go snow skiing in the morning and surfing in the evening of the same day , without having to travel long distance. Contrast abounds in California. The highest point in the United States (outside Alaska ) is in California , and so is the lowest point (including Alaska )。 Mount Whitney , 14,494 feet above sea level,is separated from Death Valley , 282 feet below sea level,by a distance of only 100 miles. The two areas have a difference in altitude of almost three miles. California has deep , clear mountain lakes like Lake Tahoe , the deepest in the country, but it also has shallow, salty desert lakes. It has Lake Tulainyo , 12,020 feet above sea level, and the lowest lake in the country , the Salton Sea, 236 feet below sea level. Some of its lakes , like Owens Lake in Death Valley , are not lakes at all: they are dried up lake beds. In addition to mountains ,lakes, valleys,deserts, and plateaus,California has its Pacific coastline, stretching longer than the coastlines of Oregon and Washington combined.
1. Which of the following is the lowest point in the United States?
A. Lake Tulainyo B. Mojave desert C. Death Valley D. The Salton Sea
2. Where is the highest point in the United States located ?
A. Lake Tahoe.
B. Sierra Nevada. C. Mount Whitney.
D. Alaska.
3. How far away is Death Valley from Mount Whitney?
A. About 3 miles.
D. 14,494 feet.
4. Which of the following is NOT mentioned in the passage as being within a radius ofabout 100 miles of Bakersfield ?
A. The Pacific Ocean.
B. San Joaquin Valley.
C. Mojave Desert.
D. Oregon andWashington.
5. Which statement best demonstrates that California is a land of variety and contrast ?
A. The highest lake in California is Lake Tulainyo.
B. It is possible to go surfing and snow skiing in some parts of California without having totravel long distance.
C. Sierra Nevada, San Joaquin Valley, Mojave Desert and the Pacific Ocean all lie withina radius of about 100 miles.
D. Owens Lake , in Death Valley , is not really a lake at all.
Scattered through the seas of the world are billions of tons of small plants and animals called plankton. Most of these plants and animals are too small for the human eye to see. They drift about lazily with the currents, providing a basic food for many larger animals. Plankton has been described as the equivalent of the grasses that grow on the dry land continents, and the comparison is an appropriate one. In potential food value however, plankton far outweighs that of the land grasses. One scientist has estimated that while grasses of the world produce about 49 billion tons of valuable carbohydrates each year. The sea’s plankton generates more than twice as much.
Despite its enormous food potential, little effort was made until recently to farm plankton as we farm grasses on land. Now marine scientists have at last begun to study this possibility, especially as the sea’s resources loom even more important as a means of feeding an expanding world population.
No one yet has seriously suggested that “planktonburgers” may soon become popular around the world. As a possible farmed supplementary food source, however, plankton is gaining considerable interest among marine scientists.
One type of plankton that seems to have great harvest possibilities is a tiny shrimplike creature called krill. Growing to two or three inches long, krill provide the major food for the giant blue whale, the largest animal ever to inhabit the Earth. Realizing that this whale may grow 100 feet and weigh 150 tons at maturity, it is not surprising that each one devours more than one ton of krill daily.
Krill swim about just below the surface in huge schools sometimes miles wide, mainly in the cold Antarctic. Because of their pink color, they often appear as a solid reddish mass when viewed from a ship or from the air. Krill are very high in food value. A pound of these crustaceans contains about 460 calories—about the same as shrimp or lobster, to which they are related.
If the krill can feed such huge creatures as whales, many scientists reason, they must certainly be contenders as new food source for humans.
1.Which of the following best portrays the organization of the passage?
A.The author presents the advantages and disadvantages of plankton as a food source.
B.The author quotes public opinion to support the argument for farming plankton.
C.The author classifies the different food sources according to amount of carbohydrate.
D.The author makes a general statement about plankton as a food source and then moves to a specific example.
2.According to the passage, why is plankton regarded to be more valuable than land grasses?
A.It is easier to cultivate.
B.It produces more carbohydrates.
C.It does not require soil.
D.It is more palatable.
3.Why does the author mention “planktonburgers”?
A.To describe the appearance of one type of plankton.
B.To illustrate how much plankton a whale consumes.
C.To suggest plankton as a possible food sources.
D.To compare the food values of beef and plankton.
4.What is mentioned as one conspicuous feature of krill?
A.They are the smallest marine animals.
B.They are pink in color.
C.They are similar in size to lobsters.
D.They have grass like bodies.
5.The author mentions all of the following as reasons why plankton could be considered a human food source except that it is ___.
A.high in food value.
B.in abundant supply in the oceans.
C.an appropriate food for other animals.
D.free of chemicals and pollutants.
As the number of people involved in an organization increase, the use of written communication rises even faster. Instead of a quick conversation to sort something out numerous messages can be passed backwards and forwards. This can lead to a tremendous amount of paperwork and is often less effective than face-to-face communication. When you are actually talking to someone you can discuss things until you are happy that they have understood and feedback is immediate. With written messages, however, you are never quite sure how it will be received what you think you have said and what the other person thinks you have said can be very different.
The amount of written information generated in large organizations today can lead to communication overload. So much information is gathered that it gets in the way of making decisions. Take a look at the average manager's desk and you will see the problem -- it is often covered with letters, reports and memos. This overload can lead to inefficiencies. For example, managers may not be able to find the information they want when they need it. Communication is also becoming more difficult with the changes occurring in employment patterns. With more people working part-time and working at home, managing communication is becoming increasingly complex.
1.In the first paragraph the writer recommends that communication with staff should includeA. some feedback on their job performance.
B. an explanation of how company targets have been set.
C. information on promotion prospects within the company.
D. an indication of which duties they can expect assistance with.areas they could improve
2.According to the writer, the best way of achieving effective communication is toA. adapt the message to suit a particular audience.
B. make the content of messages brief and direct.
C. select the most suitable means of conveying a particular message.
D. ensure that information is targeted at the appropriate group of people.
3.What does the writer say about the communication options available to senior managers?A. Sending memos to staff is one of the most efficient methods.
B. It is important to find the time to discuss certain matters with staff.
C. They should increase the range of options that they use.
D. Getting junior managers to talk to staff can create different problems.
4.What advice is given about the communication tools made available by technology?A. Aim to limit staff use of certain communication tools.
B. Evaluate them in terms of the expenditure involved.
C. Select them on the basis of the facilities they offer.
D. Encourage more staff to attend training courses in their use.
5.According to the writer, a problem with written communication is thatA. the message can be interpreted differently to what was intended.
B. it can be easy for people to ignore the contents of a written message.
C. most people are more comfortable with face-to-face communication.
D. it is possible for correspondence to get lost within a large organization.
6.According to the article, what is the effect of receiving large amounts of written information?A. It is counter-productive. "
B. It causes conflict in a company.
C. It leads to changes in work patterns.
D. It makes the main points more difficult to identify.
试题">The Importance of Good Communications
Effective communication is essential for all organizations. It links the activities of the various parts of the organization and ensures that everyone is working towards a common goal. It is also extremely important for motivating employees. Staff need to know how they are getting on, what they are doing right and in which areas they could improve. Working alone can be extremely difficult and it is much easier if someone takes an interest and provides support. Employees need to understand why their job is important and how it contributes to the overall success of the firm. Personal communication should also include target setting. People usually respond well to goals, provided these are agreed between the manager and subordinate and not imposed.
However, firms often have communication problems that can undermine their performance. In many cases,these problems occur because messages are passed on in an inappropriate way. There are, of course, several ways of conveying information to others in the organization which include speaking to them directly, e-mailing, telephoning or sending a memo. The most appropriate method depends on what exactly it is you are communicating. For example, anything that is particularly sensitive or confidential, such as an employee's appraisal, should be done face-to-face.
One of the main problems for senior executives is that they do not have the time or resources needed to communicate effectively. In large companies, for example, it is impossible for senior managers to meet and discuss progress with each employee individually. Obviously this task can be delegated but at the cost of creating a gap between senior management and staff. As a result, managers are often forced to use other methods of communication, like memos or notes, even if they know these are not necessarily the most suitable means of passing on messages.
The use of technology, such as e-mail, mobile phones and network systems, is speeding up communication immensely. However, this does not mean that more investment in technology automatically proves beneficial: systems can become outdated or employees may lack appropriate training. There are many communications tools now available but a firm cannot afford all of them. Even if it could, it does not actually need them all.The potential gains must be weighed up against the costs, and firms should realize that more communicationdoes not necessarily mean better communication."
As the number of people involved in an organization increase, the use of written communication rises even faster. Instead of a quick conversation to sort something out numerous messages can be passed backwards and forwards. This can lead to a tremendous amount of paperwork and is often less effective than face-to-face communication. When you are actually talking to someone you can discuss things until you are happy that they have understood and feedback is immediate. With written messages, however, you are never quite sure how it will be received what you think you have said and what the other person thinks you have said can be very different.
The amount of written information generated in large organizations today can lead to communication overload. So much information is gathered that it gets in the way of making decisions. Take a look at the average manager's desk and you will see the problem -- it is often covered with letters, reports and memos. This overload can lead to inefficiencies. For example, managers may not be able to find the information they want when they need it. Communication is also becoming more difficult with the changes occurring in employment patterns. With more people working part-time and working at home, managing communication is becoming increasingly complex.
1.In the first paragraph the writer recommends that communication with staff should includeA. some feedback on their job performance.
B. an explanation of how company targets have been set.
C. information on promotion prospects within the company.
D. an indication of which duties they can expect assistance with.areas they could improve
2.According to the writer, the best way of achieving effective communication is toA. adapt the message to suit a particular audience.
B. make the content of messages brief and direct.
C. select the most suitable means of conveying a particular message.
D. ensure that information is targeted at the appropriate group of people.
3.What does the writer say about the communication options available to senior managers?A. Sending memos to staff is one of the most efficient methods.
B. It is important to find the time to discuss certain matters with staff.
C. They should increase the range of options that they use.
D. Getting junior managers to talk to staff can create different problems.
4.What advice is given about the communication tools made available by technology?A. Aim to limit staff use of certain communication tools.
B. Evaluate them in terms of the expenditure involved.
C. Select them on the basis of the facilities they offer.
D. Encourage more staff to attend training courses in their use.
5.According to the writer, a problem with written communication is thatA. the message can be interpreted differently to what was intended.
B. it can be easy for people to ignore the contents of a written message.
C. most people are more comfortable with face-to-face communication.
D. it is possible for correspondence to get lost within a large organization.
6.According to the article, what is the effect of receiving large amounts of written information?A. It is counter-productive. "
B. It causes conflict in a company.
C. It leads to changes in work patterns.
D. It makes the main points more difficult to identify.
Part IV Translation
As the source of aluminum is almost inexhaustible, we can expect that more and more uses will be found for this versatile metal. (Passage Two)
题目:Reassessment of job satisfaction
汉译英:手机改变了人与人之间的关系。 通常有注意到会议室的门上的告示,写着―关闭手机。‖然而,会议室仍然充满着铃声。我们都是普通人,没有很多重要的事情。但是,我们也不愿轻易关闭手机。打开手机象征着我们与世界的联系。 手机反映出我们的社交饥渴。我们经常看到,一个人走着走着,就突然停下来了,眼睛盯着他的手机,不管他在那里,无论是在道路中心或旁边有厕所。
Many people believe that scientific research should be carried out and controlled by the government rather than private companies. To what extent do you agree or disagree?