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BC Science 8 Chapter 3 3.1 The Immune System Infectious Diseases - are caused by pathogens Pathogen - an organism or substance that can cause a disease Antigen - is a non-living particle or substance that the body cannot recognize (ex. A virus) Phagocytes - white blood cells that fight Infections 4 Ways to Transmit Infectious Diseases Transmission Method Example Direct Contact Shaking hands or sharing drinking containers or bodily fluids with an infected person Indirect Contact Being near an infected person who sneezes without covering his or her mouth. Some pathogens can travel up to 5 m and infect people within that range Water and Food Eating foods, such as eggs and some meats that are infected with Salmonella bacteria. Drinking water infected with E. Coli bacteria can also result in serious illness. Animal Bites Being bitten by an animal carrying the rabies virus Eric Hamber Secondary BC Science 8 – Chapter 3 1 How does the Immune System protect the body? The immune system is the body’s defence system. The immune system attacks and destroys invaders such as pathogens entering the body 2 lines of defence First Line of Defence The first line of defence is the skin and the linings of the body’s internal systems. The skin stops many pathogens from entering the body. Sweat and oils on your skins can kill pathogens. Gastric juice can destroy pathogens that enter the stomach. Mucus and cilia in your nose prevent pathogens from entering your respiratory system. Figure 3.3 Eric Hamber Secondary BC Science 8 – Chapter 3 2 The Second Line of Defence The second line of defence is to respond to pathogens by attacking them. 2 ways the immune system attacks pathogens are an innate immune response and an acquired immune response. Innate Immune Response Is a quick, general response that all living things are born with. When pathogens attack, the body makes more white blood cells or phagocytes (the blood cells that fight infections) The white blood cells are sent to the infected part of the body, causing a fever, swelling, and redness in the area (inflammation). The white blood cells (phagocytes) swallow up the invading pathogens. Figure 3.5 Eric Hamber Secondary BC Science 8 – Chapter 3 figure 3.6 3 Acquired Immune Response An acquired immune response is a specific attack on a particular pathogen, or antigen and there are 2 ways the body can mount an attack. Both ways involve types of white blood called B cells and T cells B cells Recognize antigens in the body Produce antibodies to fight the antigens Antibodies attach to and destroy antigens and pathogens carrying antigens. Figure 3.7 Eric Hamber Secondary BC Science 8 – Chapter 3 4 T Cells – Helper T Cell and Killer T Cells White blood cells recognize an antigen or pathogen and signal for helper T cells which activate B cells to produce antibodies to attack them The antibodies then destroy the antigen or pathogen Some of the antibodies stay in the body to protect against future infections (immunity) Figure 3.8 Killer T cells can work independently and directly destroy antigens or pathogens Figure 3.9 Eric Hamber Secondary BC Science 8 – Chapter 3 5 Active Immunity All Acquired immune responses help give you active immunity. This means your body remembers which antibodies should be used to attack a pathogen that has infected it before After the first infection, your body stores some of the newly produced antibodies on B cells B cells or memory B cells can be re-activated if the antigen or pathogen reappears. 3.2 Factors Affecting the Immune System Mary Montagu - discovered a way or protecting children from smallpox by making a scratch on a child’s arm and placing a drop of pus from a mildly infected person onto the scratch. Children would recover quickly from a milder version of smallpox Edward Jenner - 1796, discovered that people who milked cows seemed to be immune to smallpox because they had previously had cowpox. (If people got cowpox; they could not get smallpox) Vaccine - is a weakened or dead form of a disease pathogen. A vaccine is a special version of an antigen that gives you immunity against a disease Eric Hamber Secondary BC Science 8 – Chapter 3 6 Allergy - your immune system is very substance, such as dust, mould, or some foods Allergen - any substance that causes an allergic reaction (ex. Runny nose, watery eyes) Histamine - a chemical the immune system releases to combat allergens when they enter the body Anaphylactic shock - a severe reaction from exposure to Allergens (ex. Bee sting venom and Peanuts) ….reactions like swelling, Breathing difficulty, and sometimes Death. Carrying an adrenaline autoInjector to inject adrenaline into the Body to counter the allergic reaction AIDS (Acquired Immunodeficiency Syndrome) - a disease that is caused by a type of virus called HIV HIV (Human Immunodeficiency Virus) - a pathogen that attacks the helper T cells of the immune system and without helper T cells, the body cannot trigger the action of killer T cells or B cells (a person can get very sick or die from infections) diagram Eric Hamber Secondary BC Science 8 – Chapter 3 7 Taking Care of Your Immune System Eat a well balanced diet. Maintain your personal hygiene – brush your teeth, shower or bathe, and wash your hands often. Keep your home clean. Avoid tobacco and other non-prescription drugs. Get plenty of rest and exercise. Keep your vaccinations up to date. Do not engage in activities that involve sharing body fluids with others. Eric Hamber Secondary BC Science 8 – Chapter 3 8