topic b3- infection and response

• communicable disease

  a disease that can be spread between people
• 4 main types of pathogens for a communicable disease

  • bacteria
  • protist
  • fungi
  • virus
  • air, direct contact, water
• bacteria- salmonella

  protist- malaria

  fungi- athlete's foot

  virus- TMV
• prevent disease

  • staying hygienic- washing hands
  • self isolation- if you have a disease (avoid infection)
  • vaccination- build up herd immunity
  • destroying vectors- using insecticides
• communicable disease

  simply a disease that can spread
• mains way of spreading

  • water- cholera
  • air- influenza virus
  • direct contact- athlete's foot
• bacteria

  • very small cells
  • produce toxins that damage your cells
  • salmonella and gonorrhoea are two examples
• virus

  • not cells
  • they use body cells as 'hosts' and replicate inside of them
  • antibiotics don't work on them
  • measles and HIV are two examples
• fungi

  • can be single celled or multi-cellular
  • have a body like structure called hyphae
  • rose back spot is an example, it causes black spots to form on plant leaves, causing reduced photosynthesis
• protist

  • eukaryotic cells, mostly single celled
  • some are parasites, that live on/in an organism, transferred there by a vector
  • malaria is the most common protist, where mosquitoes are the vector and transfer the malaria parasite onto organisms
• how many lines of defence are there

  three
• first line of defence

  • skin
  • hairs- nose + ears
  • mucus- throat + nose
  • stomach acid
  • enzymes in tears
• second line of defence

  • white blood cells- phagocytosis
  • phagocytes hunt down pathogens as they bind together by antibodies
  • phagocytes proceed to digest pathogens
• third line of defence

  • white blood cells- lymphocytes- help remember specific pathogens
  • lymphocytes- make antibodies + memory cells
  • if pathogen enters bloodstream again, quickly make antibodies + fight it off immediately
• explain how a vaccine works in preventing disease/ reducing the spread of disease

  • A vaccine contains a dead or weakened form of the pathogen.
  • The immune system detects (white blood cell engulfs the pathogen + remembers + store antibodies for that pathogen) the antigens on the pathogen and produces specific antibodies.
  • Memory cells are created, which remain in the bloodstream.
  • If the real pathogen enters the body later, the immune system responds quickly by producing (mass amounts of) antibodies, (to destroy pathogen + reduces harm to the body) preventing illness.
• drug development

  • stage 1- drug modelling on computer program
  • stage 2- testing on human cells + tissues- see reaction
  • stage 3- testing on animals- mimicking humans
  • stage 4- clinical trials with human volunteers, double blind + placebo
  • passed, put out to public, for prescriptions
• placebo

  • fake version of a drug
  • used to remove psychological effects of medication
• double blind trial

  • where patients + doctors both don't know who has the placebo or real medication
  • used to remove bias in results
  • used to test for:
  • efficacy
  • dosage
  • toxicity
• efficacy

  how effective it is
• dosage

  how much patients need
• toxicity

  to measure any side effects