【正文】 the adoption of an approach to space in which all parts of the canvas played an equally vital role in the total work。 and there are some of each type in the brain. These terms are used because nicotine mimics the action of acetylcholine at nicotinic receptors, whereas muscarine, an alkaloid from the mushroom Amanita muscaria, mimics the action of acetylcholine at the muscarinic receptors. Acetylcholine is the neurotransmitter produced by neurons referred to as cholinergic neurons. In the peripheral nervous system acetylcholine plays a role in skeletal muscle movement, as well as in the regulation of smooth muscle and cardiac muscle. In the central nervous system acetylcholine is believed to be involved in learning, memory, and mood. Acetylcholine is synthesized from choline and acetyl coenzyme A through the action of the enzyme choline acetyltransferase and bees packaged into membranebound vesicles . After the arrival of a nerve signal at the termination of an axon, the vesicles fuse with the cell membrane, causing the release of acetylcholine into the synaptic cleft . For the nerve signal to continue, acetylcholine must diffuse to another nearby neuron or muscle cell, where it will bind and activate a receptor protein. There are two main types of cholinergic receptors, nicotinic and muscarinic. Nicotinic receptors are located at synapses between two neurons and at synapses between neurons and skeletal muscle cells. Upon activation a nicotinic receptor acts as a channel for the movement of ions into and out of the neuron, directly resulting in depolarization of the neuron. Muscarinic receptors, located at the synapses of nerves with smooth or cardiac muscle, trigger a chain of chemical events referred to as signal transduction. For a cholinergic neuron to receive another impulse, acetylcholine must be released from the receptor to which it has bound. This will only happen if the concentration of acetylcholine in the synaptic cleft is very low. Low synaptic concentrations of acetylcholine can be maintained via a hydrolysis reaction catalyzed by the enzyme acetylcholinesterase. This enzyme hydrolyzes acetylcholine into acetic acid and choline. If acetylcholinesterase activity is inhibited, the synaptic concentration of acetylcholine will remain higher than normal. If this inhibition is irreversible, as in the case of exposure to many nerve gases and some pesticides, sweating, bronchial constriction, convulsions, paralysis, and possibly death can occur. Although irreversible inhibition is dangerous, beneficial effects may be derived from transient (reversible) inhibition. Drugs that inhibit acetylcholinesterase in a reversible manner have been shown to improve memory in some people with Alzheimer39。 9) no + 比較級(jí) + than 的結(jié)構(gòu)表示 A 和 B 一樣不 …… 。例如： The car runs faster than 110 miles. 那輛車時(shí)速為 110多英里。前一個(gè)句型結(jié)構(gòu)表示的意義是 越（怎么樣就）越（怎么樣） ，在這個(gè)結(jié)構(gòu)中的兩個(gè) 比較級(jí) 不要求一定詞性相同，它們各自的詞性要依句子的需要而定；后一個(gè)句型結(jié)構(gòu)表示的意義是 越來(lái)越（怎么樣） ，在這個(gè)結(jié)構(gòu)中的兩個(gè) 比較級(jí) 則要求詞性相同。 This street is narrower than that one. 這條街比那條街窄一些。 She hasn39。s. 他的寢室沒(méi)有他姐姐的整潔。 3) 形容詞的最高級(jí)前一般必須有定冠詞 the；但是也有不加定冠詞 the的幾種情況。學(xué)習(xí)目標(biāo)：學(xué)習(xí)與冒險(xiǎn)和度假活動(dòng)相關(guān)的詞匯；復(fù)習(xí)動(dòng)詞 to get 的用法；學(xué)習(xí)級(jí)別形容詞和極限形容詞；復(fù)習(xí)過(guò)去分詞和現(xiàn)在分詞用作形容詞。另外， every 可用于 [ every other (或 every +數(shù)詞 ) + 名詞 ]的結(jié)構(gòu)中，表示 每隔 …… 之意思： every other day 每隔一天 every three years 每隔三年 every third year 每隔三年 every other line 每隔一行 every ten miles 每隔十哩 Unit3136 學(xué)習(xí)內(nèi)容及目標(biāo) 課時(shí)分配：布置學(xué)習(xí)及內(nèi)容簡(jiǎn)介 1 課時(shí)；面授 3 課時(shí)；答疑解惑 2 課時(shí)。 Even if they were to fail, they wouldn39。學(xué)習(xí)目標(biāo)：學(xué)習(xí)描述科技發(fā)展的詞匯；復(fù)習(xí)被動(dòng)語(yǔ) 態(tài)；復(fù)習(xí)含有情態(tài)動(dòng)詞的被動(dòng)語(yǔ)態(tài)；學(xué)習(xí)議論文的結(jié)構(gòu)；復(fù)習(xí)連接詞語(yǔ)的用法。 Unit2530 學(xué)習(xí)內(nèi)容及目標(biāo) 課時(shí)分配：布置學(xué)習(xí)及內(nèi)容簡(jiǎn)介 1 課時(shí)；面授 3 課時(shí)；答疑解惑 2 課時(shí)。 We happened to have e across the article once .我們碰巧有一次見(jiàn)過(guò)這篇文章。 What shall we be doing next ? 我們干什么？ If you don39。 What will you be doing tomorrow morning? 明天上午你做什么？ It won39。例如： I may not e to see you recently unless I can plete the project ahead of time .除非我能提前完成那個(gè)項(xiàng)目，否則我最近不會(huì)來(lái)看你了。 在復(fù)合賓語(yǔ)結(jié)構(gòu)中，有些動(dòng)詞如： feel , hear , notice see , watch 等后面既可以用現(xiàn)在分詞作賓語(yǔ)補(bǔ)足語(yǔ)，也可用不帶 to的不定式來(lái)充當(dāng)。 My sister was heard singing that song in English outside. （主語(yǔ)補(bǔ)足語(yǔ)）有人聽(tīng)到我妹妹在外面用英文唱那首歌。例如： The game being over, the audience stood up and cheered for the winner. （表示時(shí)間）比賽結(jié)束時(shí)，觀眾站起來(lái)為勝者歡呼。 另外， 若想明確表示分詞動(dòng)作發(fā)生在謂語(yǔ)動(dòng)作之前，可用分詞的完成形式（其中包括主動(dòng)式和被動(dòng)式）： Having + 過(guò)去分詞 （主動(dòng)式）， Having + been + 過(guò)去分詞 （被動(dòng)式）。 Laughing and talking loudly, the audience left the stadium after the match. （表示伴隨性的方式）比賽結(jié)束后，觀眾們大聲說(shuō)著，笑著離開(kāi)了賽場(chǎng)。也就是說(shuō)，我們總是選一個(gè)最重要的動(dòng)作為句子的謂語(yǔ)，而把其它的次要?jiǎng)幼鲗懗煞衷~形式。 She looked disappointed after she lost the game. 輸?shù)裟菆?chǎng)比賽后，她看上去很失望。 另外，分詞作定語(yǔ)還有 being + 過(guò)去分詞 的形式。 1）作定語(yǔ) 單個(gè)分詞作定語(yǔ)，分詞一般說(shuō)來(lái)寫在被修飾的名詞、代詞之前；分詞短語(yǔ)作定語(yǔ)時(shí)，分詞放在被修飾詞之后。 Mother heard the door opened . 媽媽聽(tīng)見(jiàn)門打開(kāi)了。 現(xiàn)在我們用實(shí)例來(lái)說(shuō)明分詞的這兩大區(qū)別。 分清現(xiàn)在分詞與過(guò)去分詞的區(qū)別是我們決定用何詞形式的重要依據(jù)。因此，在討論分詞的句法作用之前，讓我們先討論一下這兩個(gè)概念問(wèn)題。學(xué)習(xí)目標(biāo)：學(xué)習(xí)與語(yǔ)言相關(guān)的詞匯；學(xué)習(xí)不定式的進(jìn)行式； be going to 表示預(yù)測(cè)；復(fù)習(xí) so 的用法；復(fù)習(xí)將來(lái)完成時(shí)； likely, probably 和 possibly 的用法。課時(shí)分配：布置學(xué)習(xí)及內(nèi)容簡(jiǎn)介 1 課時(shí)；面授 3 課時(shí)；答疑解惑 2 課時(shí)。 第 23 單元 在本單元中，你將學(xué)習(xí)了解世界媒體是如何 報(bào)導(dǎo)新聞的。 這里所說(shuō)的 分詞的動(dòng)作意義 是指拋開(kāi)它的形式，只談 動(dòng)作表達(dá)的意思 。下面我們看看這兩種分詞形式的區(qū)別： 現(xiàn)在分詞 : 1）分詞和與其相關(guān)的名詞、代詞之間構(gòu)成 一種 主謂關(guān)系 ，即 主動(dòng)態(tài) 。 例一 I don39。 例二 China belongs to developing countries . 中國(guó)屬于發(fā)展中國(guó)家。 現(xiàn)在分詞作定語(yǔ)，主要說(shuō)明 正在進(jìn)行的動(dòng)作 或是 一個(gè)在現(xiàn)在或過(guò)去某段時(shí)間內(nèi)的經(jīng)?；瘎?dòng)作 。這種表達(dá)形式的意義是 分詞動(dòng)作正在進(jìn)行；但分詞動(dòng)作與其所修飾的詞之間是動(dòng)賓關(guān)系 。 What he said sounds convincing. 他的話聽(tīng)起來(lái)很有說(shuō)服力。 上述的情況也可視為使用分詞作狀語(yǔ)的前提條件。 Surrounded by his students , the professor sat there cheerfully . （表示伴隨 性的方式）那位教授在學(xué)生們的簇?fù)硐拢d高采烈地坐在那兒。 分詞作狀語(yǔ)還有 being + 過(guò)去分詞 的形式。 The decision having been made, they began to think of how to carry it out . （表示時(shí)間）決議已經(jīng)作出，他們開(kāi)始考慮 怎樣執(zhí)行它。 They once heard the song sung in English. （賓語(yǔ)補(bǔ)足語(yǔ)）他們?cè)?tīng)見(jiàn)有人用英文唱那首歌。但這兩種情況在表達(dá)的意義上有所不相同：用現(xiàn)在分詞作賓語(yǔ)補(bǔ)足語(yǔ)，強(qiáng)調(diào)分詞動(dòng)作在發(fā)生和進(jìn)行之中；用不帶 to的不定式來(lái)充當(dāng)賓語(yǔ)補(bǔ)足語(yǔ)，則著重說(shuō)明不定式動(dòng)作從發(fā)生到結(jié)束的全過(guò)程?；蛘撸撼俏夷芴崆巴瓿赡莻€(gè)項(xiàng)目，我最近才會(huì)來(lái)看你了。t be long before that we will be making a new puter for more advanced calculation. 不久我們就要造一部新計(jì)算器進(jìn)行更高級(jí)的運(yùn)算。t do so , you will be facing great difficulties. 你如果不這樣做就會(huì)面臨很大的困難。 不定式的 完成式 則表示不定式的動(dòng)作業(yè)已發(fā)生 ，并 發(fā)生于謂語(yǔ)動(dòng)作之先 。