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Class: Name: ( ) Date: 20 Defence against diseases 20.1 What is body defence? (Book 3, p.86) (1) Body defence (身體防衛) is the protective function of our body against diseases. (2) Pathogens are micro-organisms which cause diseases. Examples include bacteria and viruses. The two main types of defence methods: 1 those that prevents pathogens from entering the body 2 those that fight against the invading pathogens Our body protects us against pathogens 20.2 What are the non-specific defence methods? (Book 3, p.87) (3) Non-specific defence methods (非專一性的防衛方法) prevent all types of pathogens from causing diseases. Their actions are non-specific (非專一性的). Possible entrances through which pathogens may enter our body: Reproductive systems Respiratory system Digestive system Physical barriers and chemical barriers form the (4) of defence first line (第一道防線). Certificate Biology - New Mastering Basic Concepts Oxford University Press 2005 33 Class: Name: ( ) Date: Physical barriers (Book 3, p.87) (1) Physical barriers (物理屏障) are the physical structures that prevent pathogens from entering the body. Physical barriers include: Skin covers the whole body. Its outer layer of (2) dead cells in the epidermis stops the entry of pathogens. Skin In the ciliated epithelium of the respiratory tract, (3) mucus from the mucus-secreting cells trap pathogens. The beating action of (4) cilia moves the trapped pathogen to the pharynx for swallowing or coughing out. Respiratory tract Chemical barriers (Book 3, p.87) (5) Chemical barriers (化學屏障) are chemical secretions that may kill or stop the growth of pathogens, hence preventing them from entering the body. Chemical barriers include: (6) Sebum secreted by the sebaceous glands of the skin acts as a natural (7) antiseptic (消毒劑) to kill pathogens on the skin. Skin 34 Certificate Biology - New Mastering Basic Concepts Oxford University Press 2005 Class: Name: ( ) Date: Gastric juice secreted in stomach contains (1) hydrochloric acid to kill pathogens in food. Stomach (2) Tears secreted by the tear glands of the eyes acts as a natural antiseptic to kill pathogens on the conjunctiva. Eye Phagocytosis (Book 3, p.88) (3) Phagocytosis (4) phagocytes is the process in which pathogens are engulfed by (吞噬細胞). Phagocytes kill the engulfed pathogens by digesting them with (5) enzymes . Phagocytosis and digestion of a pathogen Certificate Biology - New Mastering Basic Concepts Oxford University Press 2005 35 Class: Name: ( ) Date: Inflammatory response (Book 3, p.89) Events in an inflammatory response: 1 (1) 2 wound on skin Arterioles in the infected area dilate . Blood capillaries (2) pathogen increases their permeability. phagocyte 3 More blood flows into the infected area. 4 More (3) phagocytes come out of the capillaries to engulf and kill the capillary invading pathogens. Inflammatory response (4) Inflammation painful. (5) (發炎) Pus occurs when the infected area becomes red, swollen and (膿) may form inside the wound. Go To … Section concept diagram (Student’s Book 3 p.90) Quick check (Student’s Book 3 p.90) 20.3 What are the specific defence methods? (Book 3, p.91) (6) Specific defence immune responses (免疫反應) in which (7) methods antibodies (專一性的防衛方法) are the (抗體) are produced to act against antigens. They are more powerful than the non-specific methods. Production of antibodies (Book 3, p.91) (8) (9) Lymphocytes antigens in blood and lymph nodes detect (抗原) on the surfaces of pathogens to produce antibodies. Each kind of antibodies is (10) in action. 36 specific (專一性的) The Y-shaped antibodies Certificate Biology - New Mastering Basic Concepts Oxford University Press 2005 Class: Name: ( ) Date: Antibodies can act against pathogens in the following ways: 1 (1) Lysis (溶菌作用) of a pathogen antigen antibodies hole pathogen (bacterium or virus) 2 Helping in (2) antibodies attach to pathogen and start processes to make holes pathogen is lysed (被溶解) and killed phagocytosis phagocyte pathogen antibody antibodies attach to the pathogen phagocyte detects and engulfs the pathogen 3 Making pathogens into (3) antibodies 4 Acting as (4) clumps pathogens antitoxins antibodies Certificate Biology - New Mastering Basic Concepts Oxford University Press 2005 pathogen is killed by phagocytosis (抗毒素) to toxins pathogens stuck together by antibodies cannot reproduce or enter cells neutralize toxins antibodies act as antitoxins to neutralize toxins 37 Class: Name: ( ) Date: Primary and secondary immune responses (Book 3, p.93) When a type of pathogen enters the body for the first time, it stimulates the production of antibodies. This response is called the (1) Some lymphocytes become (2) primary memory response cells (原發反應). to memorize the kind of pathogens that have entered the body. antigen undergo cell divisions first encounter produce antibodies against antigens pathogen lymphocyte activated by antigen become memory cells The primary response Next time when the same pathogen enters the body, it is recognized by the memory cells which then quickly initiate a (3) secondary The secondary response produces a (4) antibodies of the same kind in much (5) response larger shorter (繼發反應). amount of lymphocytes and time to destroy the pathogen. Changes in antibody level in the blood during primary and secondary responses to the same pathogen 38 Certificate Biology - New Mastering Basic Concepts Oxford University Press 2005 Class: Name: ( ) Date: Go To … Quick check (Student’s Book 3 p.94) STS connection 20.1 Enhancement of immunity by the intake of ‘health food’ (Student’s Book 3 p.94) E 20.4 What is the principle of vaccination? (Book 3, p.95) (1) Vaccination (疫苗接種) is the injection of controlled amounts of a weakened or dead pathogen, or an altered form of a pathogen, which has been made harmless. These injections, called (2) vaccines (疫苗), contain the antigens normally present on the surface of the pathogen. Vaccination makes use of the specificity and memory abilities of the immune system. The vaccine produces a (3) primary active pathogen of the vaccine will lead to a (4) response . Any subsequent infection by the secondary response , giving enhanced resistance to the disease. Go To … STS connection 20.2 Stories of the development of vaccination (Student’s Book 3 p.95; Activity Book 3 p.45) Section concept diagram (Student’s Book 3 p.96) Quick check (Student’s Book 3 p.96) STS connection 20.3 Relation of immunization programmes to the control of infectious diseases (Student’s Book 3 p.97; Activity Book 3 p.48) Review (Student’s Book 3 p.97) Summary concept diagram (Student’s Book 3 p.98) Note: In the 18th century, many people died of an infectious disease called smallpox (天花). Edward Jenner (17491823), a British doctor, noticed that milkmaids never came down with smallpox but a similar disease called cowpox (天花). This inspired him to put some pus collected from the boils (皮下膿腫) of a cowpox patient into the wound of a healthy boy. The boy did catch cowpox but it was only a mild disease. When the boy had recovered, Jenner put some pus collected from the boils of a smallpox patient into the wound of that boy again. Interestingly, the boy was protected against smallpox. The basis of vaccination was formed on these experiments. Certificate Biology - New Mastering Basic Concepts Oxford University Press 2005 39 Class: Name: ( ) Date: Practice question Answer the questions below with reference to the following article. China is ready to begin the second phase of human trial on vaccines against SARS (嚴重急性呼吸系統綜合症). The vaccines, containing inactivated SARS-causing viruses, were proven effective in monkeys. In 2004, the vaccines were put on first human trial. None of the healthy volunteers had abnormal reactions and SARS-neutralizing antibodies were detected in their blood. In the coming trial, researchers hope to find out how long the antibodies can remain in the volunteers. a Explain why SARS-neutralizing antibodies were detected in the blood of the volunteers. (2 marks) With the injection of vaccines, the antigens of the inactivated SARS-causing viruses (1m) stimulate the body to produce a primary response in which antibodies are produced (1m). E b How may the vaccines mentioned in the article provide protection against SARS? (4 marks) With the injection of vaccines, memory cells are produced which can memorize the type of pathogen (1m).When the body is infected later on by the SARS-causing viruses again, the body will develop a secondary response (1m). A larger amount of specific antibodies (1m) are produced in a shorter time (1m). Therefore, the body will show enhanced resistance to the SARS. E c Apart from inactivated SARS-causing viruses, suggest one other active ingredients for making vaccines against SARS. (1 mark) Dead SARS-causing viruses / Pieces of DNA of the SARS-causing viruses. (1m) E d Explain why the volunteers chosen for the trials must not be sick at the time of vaccination. (2 marks) When the volunteers are sick at the time of vaccination, the immunity of their bodies are weak (1m). They may be infected by the inactivated viruses (1m). Total: 9 marks - END - 40 Certificate Biology - New Mastering Basic Concepts Oxford University Press 2005