Fighting Disease

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  • Fighting Disease
    • Pathogens
      • Bacteria
        • Living Cells
        • 1/100th the size of body cells
        • Can reproduce rapidly
        • Make you feel ill by. . .
          • Damaging your cells
          • Producing toxins
      • Viruses
        • Not cells
        • 1/100th  the size of a bacterium
        • Replicate by...
          • Invading your cells
          • Using your cell's 'machinery' to produce many copies of themselves
          • The cell then bursts releasing all the new viruses
        • The bursting of the cell is what makes you feel ill
    • The body's defence system
      • Skin plus hairs and mucus in the respiratory tract stop a lot of microorganisms getting inside the body
      • Platelets (small fragments of cells) helps blood to clot quickly to seal a wound preventing microorganisms to get into the blood stream
      • Immune system
        • Consuming Microbes
          • White blood cells can engulf foreign cells and digest them
        • Producing Antibodies
          • Every invading cell has unique antigens on its surface
          • When a white blood cell comes across a foreign antigen it starts to produce proteins called antibodies
          • The antibodies will lock on to and kill the invading cell
          • The antibody is specific to that antigen and won't kill any others
          • Antibodies are produced rapidly and are carried around the body to kill any other similar bacteria or virus
          • The person is then naturally immune to that pathogen and won't get ill if they are infected by it again
        • Producing Antitoxins
          • White blood cells produce antitoxins to counter act the toxins produced by the invading bacteria
    • Vaccinations
      • The Vaccination
        • Dead or inactive microorganisms are injected into your body.
        • These carry antigens, which cause your body to produce antibodies to attack them
        • Your body remembers how to produce the antibodies so if the same but live microorganism got into your body the white blood cells could fight it off and you wouldn't become ill
        • The immunity may wear off after time or the bacteria or virus may mutate so booster vaccinations might be nesaccary
      • Advantages
        • Controls lots of infectious diseases
        • Epidemics can be prevented when large percentages of populations are vaccinated
      • Disadvantages
        • They don't always work
        • You can have a bad reaction to them
    • Drugs
      • Painkillers
        • They relieve pain and reduce symptoms
        • They don't tackle the cause of the disease
      • Antibiotics
        • They kill and prevent the growth of bacteria without killing body cells
        • Different antibiotics kill different bacteria
        • They don't kill viruses
        • Antibiotic resistance
          • Bacteria can mutate causing them to be resistant to antibiotics
          • If you have an infection some bacteria might be resistant so when you take antibiotics the resistant strains are left
          • These non-resistant strains will reproduce and the population will increase. This is an example of natural selection
          • This could lead to super bugs such as MRSA which is why doctors need to be careful that they don't over prescribe antibiotics


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