跟讀練習: Understanding the Immune System in One Video - 通過影片學習英語口語
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Hi, this is Tom from zerodefinals .com.
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This video was designed to give an overview of immunology, so that you understand all the basic features of the immune system.
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It will also help you to return to this video once you've already learned the details,
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so that you can again fit those details back into the bigger picture about how the immune system works.
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The immune system can be categorized into the innate immune system and the specific immune system.
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The innate immune system consists of the components that are already at the location of the infection
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and respond immediately with a generalized response.
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The specific immune system involves specialized T and B cells
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that are waiting in places away from the site of infection
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and then when they're activated they launch a specialized system
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that fights the specific invading pathogen the specific immune system takes a little
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while longer to recognize the infection particularly
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when a pathogen is invading the body for the first time
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so in this video we're going to cover both of these systems
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and also talk about a system called the complement system
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that works alongside the innate and specific immune systems let's look at what happens
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when a pathogen invades the body initially there are physical barriers that need to be broken before an infection can take place.
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The skin is an example of one of these barriers.
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Most invaders will get stuck at this barrier, however occasionally an invading pathogen will get through, such as when there's a cut in the skin.
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As well as the skin, there's other physical barriers, such as the mucosa of the respiratory system, the gastrointestinal tract, and the urinary tract.
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There are also chemical barriers that help destroy harmful pathogens before they can cause any infection, such as the hydrochloric acid in the stomach,
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lysozyme in sweat and tears, and lactic acid in the vagina.
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Let's look at the initial responses of the immune system once an invading pathogen has broken through the physical
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and chemical barriers to infection.
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Three things happen.
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Number one, macrophages recognize the pathogen and activate the innate immune system.
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Number two, dendritic cells pick up antigens from the pathogen
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and then head off in the blood
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and lymphatic systems to track down the relevant T and B cells of the specific immune system and activate them.
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And number three, the invading pathogen activates the complement system directly via the lectin pathway and the alternative pathway
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And we'll talk a bit more on those later
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First let's look at how the innate immune system provides an immediate response to infection
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The first to respond are the macrophages
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They recognise pathogens by specific characteristics that occur on pathogens but don't occur on cells of the body
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These characteristics are called pathogen -associated molecular patterns, or PAMPs.
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They recognise PAMPs using various receptor types, including toll -like receptors.
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At this point, I need to talk briefly about a process called phagocytosis.
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Now, phagocytosis is the process that macrophages and other phagocytes like neutrophils use in order to destroy pathogens.
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So what happens is once they've recognized the pathogen they start to wrap their cell membrane around
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that pathogen and absorb them to with inside their cell.
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The pathogen is then left inside something called a phagosome
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and this phagosome fuses with surrounding lysosomes that provide digestive enzymes
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that then break down that pathogen destroying it and also processing all of the components into harmless waste products.
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If the invading pathogens are harmless enough
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that the macrophages can deal with them alone then they're cleared and it goes no further.
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If the attacking army is too great the macrophages need help
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so they release cytokines which are signaling proteins sort of like local hormones
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that sound the alarm of an infection in the local area.
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This leads to a process called inflammation.
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One of the most important actions of these cytokines is to recruit and activate more cells of the immune system, such as macrophages, monocytes and neutrophils.
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Monocytes are precursors to macrophages that float around in the blood.
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Once they enter tissues, they differentiate into macrophages and can then carry out all the processes that macrophages normally carry out.
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Neutrophils are another type of phagocyte that circulate in the blood and can enter the tissues and help by destroying invading pathogens.
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The inflammatory response also involves a number of other processes that help to contain and fight the infection.
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These are vasodilation, increased vascular permeability, mast cell activation and degranulation,
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releasing more cytokines that further stimulate the inflammatory response, activation of the clotting system, and activation of the kinin system.
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Inflammation itself actually stimulates macrophages and neutrophils to secrete more cytokines, notably chemicals called interleukins.
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This is known as the acute phase response, and it leads to a more systemic inflammatory response.
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this involves sending cytokines specifically interleukin 1 to the brain to tell it to produce a fever
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that leads to high temperatures that are poorly tolerated by many pathogens
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and cause reduced appetite and lethargy so that the person conserves more energy
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that can be used to fight the infection
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it also involves sending interleukin 6 to the liver to produce acute phase protein
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that act as something called opsonins and remember this word
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because we'll talk about opsonins in a minute additionally interleukin 8 is released
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that recruits and activates more neutrophils interleukin 2
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and 12 activate natural killer cells and tumor necrosis factor alpha is released
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that does all of these effects by itself as i just mentioned
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i want to take a quick look at opsonins as these are very important in the immune system.
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Opsonins are complex molecules that attach themselves to pathogens
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and make it easier for macrophages and neutrophils to recognize and phagocytose that pathogen.
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I think of them a bit like a fork
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that spears the pathogen so that macrophage can attach to the other end of the fork
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and then use it to eat the pathogen.
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An example of an opsonin that you may have heard of is C -reactive protein or CRP.
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CRP is produced by the liver in response to interleukin -6
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and we actually measure the level of CRP in our patients to assess how much inflammation
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there is in the body
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and it can be a really good indicator of the severity of the infection
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that our patient is suffering with so
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that summarizes the innate immune system a generalized system that recognizes
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and responds to an invading pathogen by causing an inflammatory response
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and recruiting cells
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that destroy the pathogens by phagocytosis next let's look briefly at
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the complement system the complement system works alongside the innate and the specific immune system to help them destroy pathogens
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This involves a series of complement proteins labelled C1 to C9.
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Once the complement system is triggered, the proteins start to activate each other in something called the complement cascade.
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Various products of the complement cascade have important functions such as acting as opsonins,
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triggering further inflammation and directly attacking and destroying the pathogens.
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The complement system is triggered in one of three ways
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The lectin and the alternative pathway are activated directly by pathogens
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and the classical pathway is activated by antibody -antigen complexes that arise from the specific immune system
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And that brings us nicely onto looking at the function of the specific immune system
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The specific immune system involves two characters the T and the B cells and these are both types of lymphocyte.
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They are free to float around the lymphatic system and the blood
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but they spend most of their time in the lymph node and the mucosa -associated lymphoid tissue.
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Think of these lymphoid tissues as army barracks that are full of soldiers
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that are all sat around waiting to get word of an enemy that they've specifically been trained to fight.
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Each pathogen has molecules that are unique to them.
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They're known as antigens.
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Each T cell has T cell receptors that are specific to a single type of antigen.
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B cells have antibodies on their cell membrane that, just like T cell receptors, are specific to a single type of antigen.
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The result is there's millions of different T and B cells that are all specific to a single type of antigen.
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When a new pathogen arrives and causes an infection, The T and B cells that are specific to that pathogen need to be alerted.
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The trouble is they're sat in lymphatic tissue such as lymph nodes while the infection is happening somewhere completely different.
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This is where the dendritic cell comes in.
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These cells are like messengers and they pick up the antigens at the site of the invasion,
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display them on their cell surface and then bring them through the blood and lymphatic system into the lymphatic tissue.
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When they're there all the T and B cells have a look at the antigen and see whether they recognize it.
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When the T and B cells are found that specific to that antigen, those cells become activated.
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So the specific immune response starts with the dendritic cell presenting
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the antigens on the HLA class II molecules to the CD4 cells.
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These CD4 cells, which are a type of T cell, then proliferate and become T helper cells.
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The T helper cells present antigens on their HLA class 1 molecule that can be recognized by CD8 cells, another type of T cell.
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They also secrete cytokines that are responsible for making the CD8 cells proliferate and differentiate into cytotoxic T cells.
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These T helper cells also release cytokines that stimulate B cells to proliferate
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and differentiate into plasma cells that can release large quantities of antibodies
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and memory B cells
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that hang around as part of the immune memory to respond quickly in future inflections with that specific pathogen.
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The T helper cells also travel to areas of infection and
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secrete cytokines that help to recruit monocytes and macrophages to the infected tissue
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and activate the macrophages to cause inflammation and start the process of phagocytosis.
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Cytotoxic T cells are responsible for killing cells that have been infected by pathogens, such as virally infected cells.
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To do this, they need to attach themselves to the infected cell via the T cell receptor
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and the HLA class 1 molecule expressing the relevant antigen protein on the infected cell.
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once they're attached to the virally infected cell they have two killing mechanisms
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that they can choose from the first is called granule exocytosis where they basically spray the infected cell with enzymes
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that destroy the membrane and lead to cell lysis and cell death
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the second is they can activate the fast molecule the fast molecule is like a self -destruct switch
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that once it's activated it causes the cell to undergo apoptosis.
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Plasma cells and antibodies are an essential part of the specific immune system.
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Plasma cells are B cells that have differentiated and become antibody producing cells
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and their job is to produce tons of antibodies that are specific to the invading pathogen.
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These antibodies are proteins
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that are shaped like a Y one end is variable in
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shape to match different antigens whereas the other end is fixed in shape
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and can be recognized by many cells of the immune system these proteins float around the blood
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and attach themselves to antigens that match their specific variable region
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and these antibodies help the immune system fight pathogens in a number of different ways firstly
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they can attach themselves to enemy toxins which themselves are antigens and neutralize their toxic effect.
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Secondly antibodies can attach themselves to the receptors of viruses and bacteria and prevent them from carrying out their function.
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For example it can stop viruses from being able to recognize cells
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that it may want to invade and therefore prevent the viral invasion of that cell.
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Thirdly antibodies can attach themselves to pathogens then clump together to slow the spread of that pathogen down this is called agglutination.
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Finally it can be very difficult for the simplistic receptors of macrophages and neutrophils to recognize certain pathogens.
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Antibodies can act as opsonins that are highly specific to the invading pathogen
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and by attaching themselves to that pathogen acting as upsonins they can help the macrophages
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and neutrophils to recognize and destroy that pathogen.
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That summarizes an overview of the immune system.
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I hope you found this video helpful.
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It was created as part of a set of videos
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that covers everything you need to know about the immune system for medical school
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and practicing as a doctor so go ahead and check out the rest of those videos.
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If you like this one then please like, comment
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and subscribe for more videos to you achieve success in your medical career
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you can also check out the zero to finals website where you'll find notes illustrations practice questions
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and a blog and i hope it's all useful for you and i'll see you in the next video
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本課的詞彙與口語要點
這節口語課以影片“Understanding the Immune System in One Video”為素材。 影片中反覆出現的詞有：cell, pathogen, immune, specific, macrophage。 這段影片共有 157 個句子、2165 個單詞可供跟讀。 講話部分時長為 15:11。 說話人語速平穩，每分鐘約 143 個詞，很適合跟讀。 只有 73% 的單詞屬於英語最常用的 3,000 詞，詞彙難度較高。
影片中的重點詞彙
影片中 15 個值得學習的單詞，附發音和釋義：
| 單詞 | 發音 | 釋義 |
|---|---|---|
| infection 名詞 | /ɪnˈfɛkʃən/ | 傳染 /傳染 |
| activate 動詞 | /ˈæktɪˌveɪt/ | 啟用 |
| invade 動詞 | /ɪnˈveɪd/ | 入侵, 侵入 |
| attach 動詞 | /əˈtæt͡ʃ/ | 附上, 附 |
| tissue 名詞 | /ˈtɪʃ.(j)u/ | 紙巾 |
| receptor 名詞 | /ɹɪˈsɛp.tə/ | 受體 /受體 |
| molecule 名詞 | /ˈmɑ.lɪ.kjul/ | 分子 |
| barrier 名詞 | /ˈbæɹi.ə/ | 障, 柵欄 /柵欄 |
| inflammation 名詞 | /ɪnfləˈmeɪ̯ʃən/ | 炎症, 發炎 /發炎 |
| recruit 動詞 | /ɹɪˈkɹut/ | 招聘, 徵兵 /徵兵 |
| inflammatory 形容詞 | /ɪnˈflæmət(ə)ɹi/ | 激發性 /激發性 |
| trigger 名詞 | /ˈtɹɪɡɚ/ | 扳機 /扳機 |
| plasma 名詞 | /ˈplæzmə/ | 等離子體 /等離子體 |
| float 動詞 | /fləʊt/ | 浮, 漂浮 |
| activation 名詞 | /ˌæktəˈveɪʃən/ | 啟用 |
影片中出現的短語動詞
| 單詞 | 發音 | 釋義 |
|---|---|---|
| carry out 動詞 | /ˈkæ.ɹi aʊt/ | 進行 /進行 |
| check out 動詞 | 退房 | |
| pick up 動詞 | 拾取, 撿 /撿 | |
| break down 動詞 | 壞了 /壞了, 出故障 | |
| get through 動詞 | /ɡɛt ˈθɹu/ | 度過 /度過 |
| go ahead 動詞 | /ˌɡoʊ əˈhɛd/ | 請便 /請便 |
| hang around 動詞 | 逗留 | |
| track down 動詞 | 找到, 查獲 /查獲 |
影片中的語法
說話人最常用的結構，並附上影片中的原話：
| 結構 | 影片中的用法 |
|---|---|
| 被動語態 be + 過去分詞 — 強調發生了什麼，而不是誰做的 | was designed · can be categorized · be broken |
| 現在完成時 have/has + 過去分詞 — 過去發生但與現在仍有關聯的事 | you've already learned · has broken · they've recognized |
| 定語從句 who / which + 從句 — 補充說明人或事物 | cytokines which are · cells, which are |
需要注意的發音
說話人用了 15 次縮略和弱讀形式，例如 they're, they've, we'll。請按聽到的簡短形式來說。
- “th” 音: pathway /ˈpæθˌweɪ/, pathogen /ˈpæθəd͡ʒn̩/, lethargy /ˈlɛθ ər dʒi/, thirdly /ˈθɚdli/
- “sh” 和 “zh” 音: infection /ɪnˈfɛkʃən/, tissue /ˈtɪʃ.(j)u/, inflammation /ɪnfləˈmeɪ̯ʃən/, differentiate /dɪf.əˈɹɛn.ʃi.eɪt/, activation /ˌæktəˈveɪʃən/
- 長單詞——注意重音位置: inflammation /ɪnfləˈmeɪ̯ʃən/, inflammatory /ɪnˈflæmət(ə)ɹi/, differentiate /dɪf.əˈɹɛn.ʃi.eɪt/, activation /ˌæktəˈveɪʃən/, characteristic /ˌkæɹ(ə)ktəˈɹɪstɪk/
中文母語者容易讀錯的音：
- /v/ — 不要讀成 /w/，上齒輕觸下唇: activate /ˈæktɪˌveɪt/, invade /ɪnˈveɪd/, involve /ɪnˈvɑlv/, activation /ˌæktəˈveɪʃən/, virus /ˈvaɪ.ɹəs/
- 詞尾子音 — 要讀清楚，後面不要加母音: activate /ˈæktɪˌveɪt/, invade /ɪnˈveɪd/, complement /ˈkɑmpləmənt/, attach /əˈtæt͡ʃ/, involve /ɪnˈvɑlv/
- /r/ 和 /l/ 的區別: inflammatory /ɪnˈflæmət(ə)ɹi/, briefly /ˈbɹiːfli/, variable [ˈvæɹ.i.ə.bl̩], harmless /ˈhɑɹmləs/, alarm /əˈlɑɹm/
如何用這段影片練習
- 先完整聽一遍影片，不要開口，記下不認識的單詞。
- 用正常速度逐句跟讀，每句重複到你的節奏與說話人一致為止。
- 錄下自己的聲音並與原聲對比，特別注意 infection, activate, invade 這類單詞。
什麼是跟讀法？
跟讀法 (Shadowing) 是一種有科學依據的語言學習技巧，最初開發用於專業口譯員的培訓，並由多語言者Alexander Arguelles博士普及。這個方法簡單而強大：您在聽英語母語原聲的同時立即大聲重複——就像是一個延遲1-2秒緊跟說話者的影子。與被動聽力或語法練習不同，跟讀法強迫您的大腦和口腔肌肉同時處理並模模擬實的講話模式。研究表明它能顯著提高發音準確性，語調，節奏，連讀，聽力理解和口語流利度——使其成為雅思口語備考和真實英語交流最有效的方法之一。