B1 - Disease and infection

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  • B1 - Disease and infection
    • Infectious disease
      • Infectious diseases are caused by pathogens - microorganisms which cause disease.
        • fungi - causes athletes foot
        • Bacteria - causes cholera
        • Viruses - causes flu
        • Protozoa  (single celled organisms) - eg dysentry can be caused by protozoa.
      • Antibodies
        • Every pathogen has unique molecules on the surface- these are called antigens.
          • White blood cells produce a protein called an antibody - which lock on to and kill invading cells. They are specific to one pathogen meaning they can only lock on to one.
            • Some antibodies remain in the body after its done its job - this is called a memory cell. If the body becomes infected by the same pathogen again, the body will immediately produce antibodies to kill it - the person is immune.
      • White blood cells can engulf foreign cells and digest them.
        • Antitoxins counteract the effect of any poisons produced by the foreign pathogens.
    • Preventing and treating Infectious disease
      • When you're infected with a new pathogen, it takes a long time for the white blood cells to produce an antibody to fight it.
        • To avoid this you may be immunised  against the disease.
          • in this process inactive or dead pathogens are injected into the body. These carry antigens which are harmless however they will still trigger an immune response.
            • Your white blood cells will create antibodies to fight the disease. Some cells will remain as memory cells.
      • Active immunity is where the immune system makes its own antibodies after being stimulated by a pathogen. It involves being artificially immune and naturally immune . It is usually permanent.
      • Passive immunity is where you use antibodies produced by another organism, eg antibodies passed from a mother to her baby through breast milk. this is temporary.
      • Risks: swelling, redness, if you're already ill you can't have some vaccinations, it is thought that vaccinations can cause other diseases (the MMR vaccination is thought to have links with autism).
      • Antibiotics can be used to kill bacteria without killing body cells. However they cannot kill viruses.
        • Antivirals can be used to kill viral infections. they stop viruses from reproducing.
          • Some bacteria are naturally resistant to antibiotics and misuse can lead to increased rate of development of resistant strains. (eg MRSA)
    • Cancer and drug development
      • Cancer is caused by cells dividing out of control. Tumours can be benign or malignant.
        • Benign - This is where a tumour grows until theres no more room, the cells stay where they are. This type isn't usually dangerous.
          • Malignant - The tumour grows and can spread to other sites in the body. Malignant tumours can be fatal.
            • Healthy lifestyle can reduce the risk of getting cancer - not smoking can prevent lung cancer and eating less processed meat and more fibre could prevent colon cancer.
      • 77% of patients with breat cancer survive for at least 5 years
        • 6% of those with lung cancer do
      • New drugs to prevent or treat disease need to be thoroughly tested before use. Computer models are used first of all to simulate a humans response to the drug. This isnt always accurate.
        • The drug is tested on human tissue.
          • The drug must be tested on two different live mammals.
            • There is then a clinical trial. One patient is given the drug and one is given a placebo.
              • This tells the scientist the difference the drug makes. This allows rhe placebo affect
                • When the patient expects the treatment to work and so feels better.


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