電大開(kāi)放英語(yǔ)2考試小抄-預(yù)覽頁(yè)

　

【正文】 心臟病發(fā)作 rule out 排除 be posed of 由……組成 millennium 一千年 escape system （航天飛機(jī)）脫離系統(tǒng) go as planned 按計(jì)劃進(jìn)行 語(yǔ)法： 1） 同級(jí)比較往往由 as + 形容詞 / 副詞的原形 + as的句式表達(dá)；當(dāng)然也要注意它的否定形式、以及在第一個(gè) as前加倍數(shù)或程度副詞的情況。 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。在這兩種結(jié)構(gòu)中，第一個(gè) as是副詞，而第二個(gè) as是連詞；在第二個(gè) as 的后面接名詞、句子或代詞的主格（一般不要接代詞的賓格）。s. 他的寢室沒(méi)有他姐姐的整潔。 2）另外，在 as … as 的結(jié)構(gòu)中，第一個(gè) as的前面可以加上表示倍數(shù)的詞、或是某些副詞修飾語(yǔ)： twice , ( three ) times , nearly , almost , just , exactly , not nearly（根本不） , by no means（絕不） , quite 等等。 She hasn39。 He has learned as many English words as his brother (has ) . 他已學(xué)了和他哥哥一樣多的英文單字。 This street is narrower than that one. 這條街比那條街窄一些。ve been working much harder than I have. 你一直比我工作得努力多了。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。 He became less and less satisfied with the football team39。例如： The car runs faster than 110 miles. 那輛車(chē)時(shí)速為 110多英里。在這種情況下，往往是將一個(gè)人或是一件事與其他所有的人或事相比較。 9) no + 比較級(jí) + than 的結(jié)構(gòu)表示 A 和 B 一樣不 …… 。 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。 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。s turbulent yet elegant abstract paintings, which were created by spattering paint on huge canvases placed on the floor, brought abstract expressionism before a hostile public. Willem de Kooning39。 the adoption of an approach to space in which all parts of the canvas played an equally vital role in the total wo