跟读练习: Introduction to neural cell types | Organ Systems | MCAT | Khan Academy - 通过视频学习英语口语
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In this video, I want to introduce the different types of neural cells.
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The word neural, or the prefix neuro, just refers to the nervous system, so that neural cells are cells of the nervous system.
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Neural cells work with all the other cell types of the
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body to produce the amazing range of functions of the nervous system, including consciousness, social interactions, cognition,
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emotion, movement, sensory perception, and regulation of other functions such as circulation, respiration, and digestion.
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Neural cells are divided into two big categories.
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The first are neurons, which were traditionally called nerve cells.
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And the second are glia.
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Now these can also be called neuroglia or glial cells.
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That all means the same thing.
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Neurons are named from a Greek word for nerve, while glia are named from a Greek word for glue because they are once thought to do little except glue neurons together.
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The structure of the nervous system is divided into two main parts.
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The first part is mainly made up of the brain in the head and the spinal cord in the spine.
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And this part of the nervous system is called the central nervous system.
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The other part of the nervous system is called the peripheral nervous system.
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And that's made up mostly of nerves, these long stringy structures that come out of the brain and the spinal cord.
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And they go all over the body, like down into the arms and down into the legs and into every part of the body.
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And we'll cover a lot more detail about neuroanatomy in other videos, but I just need to bring up the central
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and peripheral nervous system because the neural cells are divided up differently amongst the different systems.
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Calling neurons nerve cells is a little problematic
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because these structures in the peripheral nervous system called nerves are made up of neurons, but they also contain glial cells,
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and they contain a number of other cells that aren't neural cells at all.
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However, you'll often hear people refer to neurons as nerve cells because that was the traditional name for them.
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Neurons are found both in the central nervous system, the brain and the spinal cord, and the peripheral nervous system, in the nerves.
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But the different types of glial cells are found only in one or the other.
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Most neural cells are derived from populations of cells called neural stem cells or neural crest cells.
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And both of those cell types arise early in development in the part of the embryo called the ectoderm.
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Most neurons in glia found in the central nervous system are derived from neural stem cells,
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while most neurons in glia found in the peripheral nervous system are derived from neural crest cells.
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Now we'll go into a lot more detail about what neural stem cells are
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and neural crest cells in other videos when we cover development of the nervous system.
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Most types of both neurons and glia share some structural features of the way their cell is shaped.
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Most of them have a main part to their cell called the soma, or the cell body, that contains the nucleus and most of the organelles.
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Coming out of the soma, most of these cell types have processes, long, thin extensions that come out of the soma.
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And the processes of the different neural cells vary in number and in length and thickness and degree of branching, because some of them will be unbranched,
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and some of them will have processes that branch, sometimes a little and sometimes a lot.
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They will also vary a lot in the terminal structures at the end of their processes
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and the function of these structures and the processes.
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The function of neurons is to process and transmit information, and the function of glia is to support them in a variety of ways.
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There are many structural and functional types of both the neurons and the glia, And there are large numbers of these cells making up the nervous system.
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There are billions of neurons that form trillions of connections in the adult human nervous system.
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And there are even more glia than there are neurons.
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In subsequent videos, we'll go over the most common glia, which are astrocytes, microglia, ependymal cells, oligodendrocytes, and Schwann cells.
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There are also less common glia, such as satellite cells and olfactory and sheathing cells.
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But we'll just go over the most common types here.
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本课的词汇与口语要点
这段视频共有 45 个句子、742 个单词可供跟读。 讲话部分时长为 4:10。 说话人语速自然，每分钟约 178 个词，接近日常对话。 只有 77% 的单词属于英语最常用的 3,000 词，词汇难度较高。
视频中的重点词汇
视频中 15 个值得学习的单词，附发音和释义：
| 单词 | 发音 | 释义 |
|---|---|---|
| nerve 名词 | /nɝv/ | 神經 /神经 |
| peripheral 形容词 | /pəˈɹɪf(ə)ɹ(ə)l/ | 边缘的 |
| divide 动词 | /dɪˈvaɪd/ | 分, 分裂 |
| cord 名词 | /ˈkoɹd/ | 繩 /绳, 繩子 /绳子 |
| spinal 形容词 | /spaɪ.nəl/ | 脊的 |
| crest 名词 | /kɹɛst/ | 冠 |
| refer 动词 | /ɹɪˈfɜː/ | 談到 /谈到 |
| glue 名词 | /ɡlu/ | 膠水 /胶水, 膠 /胶 |
| thin 形容词 | /ˈθɪn/ | бә, 薄 |
| subsequent 形容词 | /ˈsʌbsɪkwənt/ | 隨後的 /随后的 |
| regulation 名词 | /ˌɹɛɡjʊˈleɪʃən/ | 規則 /规则, 規例 /规例 |
| introduce 动词 | /ˌɪntɹəˈdus/ | 介紹 /介绍, 紹介 /绍介 |
| satellite 名词 | /ˈsætəlaɪ̯t/ | 衛星 /卫星 |
| terminal 名词 | /ˈtɚmɪnəl/ | 航站, 航廈 /航厦 |
| interaction 名词 | /ˌɪn.təˈɹæk.ʃən/ | 相互作用 |
视频中出现的短语动词
| 单词 | 发音 | 释义 |
|---|---|---|
| make up 动词 | /ˌmeɪk ˈʌp/ | 組成 /组成 |
| bring up 动词 | 撫養 /抚养, 養大 /养大 |
需要注意的发音
说话人用了 6 次缩略和弱读形式，例如 we'll, aren't, you'll。请按听到的简短形式来说。
- “th” 音: thin /ˈθɪn/, thickness /ˈθɪknəs/, sheath /ʃiθ/
- “sh” 和 “zh” 音: structural /ˈstɹʌk(t͡)ʃəɹəl/, extension /ɪkˈstɛnʃən/, regulation /ˌɹɛɡjʊˈleɪʃən/, interaction /ˌɪn.təˈɹæk.ʃən/, emotion /ɪˈməʊ.ʃən/
- 长单词——注意重音位置: peripheral /pəˈɹɪf(ə)ɹ(ə)l/, regulation /ˌɹɛɡjʊˈleɪʃən/, interaction /ˌɪn.təˈɹæk.ʃən/, differently /ˈdɪf.ə.ɹənt.li/, traditionally /tɹəˈdɪʃ.ə.nə.li/
如何用这段视频练习
- 先完整听一遍视频，不要开口，记下不认识的单词。
- 先用 0.75 倍速逐句跟读，熟练之后再回到正常速度。
- 录下自己的声音并与原声对比，特别注意 nerve, peripheral, divide 这类单词。
视频中的语法
说话人最常用的结构，并附上视频中的原话：
| 结构 | 视频中的用法 |
|---|---|
| 被动语态 be + 过去分词 — 强调发生了什么，而不是谁做的 | are divided · were traditionally called · be called |
| 定语从句 who / which + 从句 — 补充说明人或事物 | neurons, which were · glia, which are |
什么是跟读法？
跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。