1 / 30

Defence Against Disease

Defence Against Disease. Noadswood Science, 2011. Defence Against Disease. To understand how the body defends itself against disease. Pathogen Barriers. Complete the pathogen barriers worksheet. Pathogen Barriers. Wax traps micro-organisms.

abel-kemp
Download Presentation

Defence Against Disease

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Defence Against Disease Noadswood Science, 2011

  2. Defence Against Disease To understand how the body defends itself against disease

  3. Pathogen Barriers Complete the pathogen barriers worksheet

  4. Pathogen Barriers Wax traps micro-organisms Tears contain an enzyme which kills micro-organisms Hairs and mucus stop micro-organisms from entering the body Saliva contains an enzyme which kills micro-organisms Blood contains white blood cells which kill any micro-organisms within the body Skin barrier stops micro-organisms from entering the body

  5. Defence The breathing organs produce mucus to cover the lining of these organs and trap the microbes The skin acts as a barrier If our skin is cut platelets seal the wound by clotting Our blood contains white blood cells How does our body defend us from micro-organisms?

  6. Passive & Active Defence • The body has different ways of protecting itself against pathogens • The first defence is passive immunity – aimed at stopping the pathogen getting into the body in the first place • The body’s passive immunity system includes: - • Skin • Mucus and cilia (tiny hairs) in the respiratory system • Acid in the stomach • Enzymes in tears • If a pathogen still manages to get into the body, the second defence takes over – this is called active immunity, and the white blood cells have key functions in this…

  7. White Blood Cells • White blood cells ingest pathogens (they do not eat them!) • White blood cells can: - • Ingest pathogens and destroy them • Produce antibodies to destroy pathogens • Produce antitoxins that neutralise the toxins released by pathogens • Pathogens are not the disease – they cause the disease!

  8. White Blood Cells • There are several different types of white blood cells, each with different functions, but they can be put into two main groups: - • Phagocytes or macrophages • Lymphocytes

  9. Phagocytes Phagocytes can easily pass through blood vessel walls into the surrounding tissue and move towards pathogens or toxins They then either ingest and absorb the pathogens or toxin; or release an enzyme to destroy them Having absorbed a pathogen, the phagocytes may also send out chemical messages that help nearby lymphocytes to identify the type of antibody needed to neutralise them

  10. Phagocytes

  11. Lymphocytes Pathogen (coated in antigens) Antibodies attach Pathogens contain certain chemicals that are foreign to the body and are called antigens Each lymphocyte carries a specific type of antibody - a protein that has a chemical 'fit' to a certain antigen When a lymphocyte with the appropriate antibody meets the antigen, the lymphocyte reproduces quickly, and makes many copies of the antibody that neutralises the pathogen White blood cell

  12. Lymphocytes

  13. Antibodies • Antibodies neutralise pathogens in a number of ways: - • They bind to pathogens and damage or destroy them • They coat pathogens, clumping them together so that they are easily ingested by phagocytes • They bind to the pathogens and release chemical signals to attract more phagocytes • Lymphocytes may also release antitoxins that stick to the appropriate toxin stopping it damaging the body

  14. Antibodies Step 1 – the white blood cell identifies the pathogen Step 2 – antibodies produced to ‘fit’ the pathogen Step 3 – antibodies fit the pathogen, ‘clumping’ them Step 4 – the white blood cell ingests the pathogen

  15. Antibodies

  16. Fighting Diseases Natural immunity – antibodies are produced by a person when needed or they are passed on by the mother during pregnancy Artificial immunity – a vaccine with dead microbes is injected tricking the body into producing antibodies ready for the real thing

  17. Vaccinations & Immunisation Vaccination – taking a vaccine as a precaution against a disease Immunisation – making an animal resistant (immune) to a disease by taking a vaccine

  18. Vaccination • People can be immunised against a pathogen through vaccination • Vaccination involves putting a small amount of an inactive form of a pathogen, or dead pathogen, into the body • Vaccines can contain: - • Live pathogens (treated to make them harmless) • Harmless fragments of the pathogen • Toxins produced by pathogens • Dead pathogens • These all act as antigens – when injected into the body, they stimulate white blood cells to produce antibodies against the pathogen

  19. Vaccination Because the vaccine contains only a weakened or harmless version of a pathogen, the vaccinated person is not in danger of developing disease - although some people may suffer a mild reaction If the person does get infected by the pathogen later, the required lymphocytes are able to reproduce rapidly and destroy it

  20. Boosters Vaccines in early childhood can give protection against many serious diseases Sometimes more than one vaccine is given at a time, like the MMR triple vaccine against mumps, measles and rubella Sometimes vaccine boosters are needed, because the immune response 'memory' weakens over time (anti-tetanus injections may need to be repeated every ten years)

  21. Vaccine Example Complete a cartoon strip to show how a vaccine works… The discuss the pros / cons of vaccines within your groups

  22. Vaccine Real pathogen for disease Vaccine for disease ( a weakened version) A preparation of dead or weakened pathogens, that is used to induce formation of antibodies or immunity against the pathogen

  23. Vaccine Injection Vaccine (pathogen) injected into the bloodstream

  24. Vaccine skin White blood cells Vaccine (pathogen) Red blood cells Blood vessel Vaccine enters the blood stream

  25. Vaccine White blood cells detect a foreign body and surround it

  26. Vaccine Antibody – this is specific to this particular vaccine (pathogen) White blood cells make antibody against the vaccine (pathogen)

  27. Vaccine White blood cells that destroy pathogens The antibody acts as a marker for other white blood cells to come along and engulf the vaccine (pathogen)

  28. Vaccine • *In passive immunity the body is actually given the antibodies – this only lasts at most a few years The vaccine (pathogen) has been destroyed and the antibody is left in the blood stream (active immunity)

  29. Vaccine Pros & Cons

  30. MMR Controversy • Research the measles, mumps rubella (MMR) vaccination controversy – was there any scientifically significant link between the MMR jab and autism… • How did Andrew Wakefield collect the data, and should he have conducted the study? • Was 12 individuals enough to warrant the study? • How should he have collected the data, and how much data should he have taken? • What long term problems has this study caused?

More Related