(10) diseases and immunity

• pathogen


  disease causing organism
• transmissible disease


  disease where pathogen can be passed from one host to another
• pathogen transmitted by


  • direct contact: blood, sex, share needles
  • indirect contact: contaminated surfaces, food, animals and air
• prevention


  • clean water supply
  • good personal hygiene
  • waste disposal
  • hygienic food preparation
  • sewege treatment
• body's defences


  • mechanical: skin, nose hair
  • chemical: mucus, stomach acid
  • white blood cells: phagocytes, lymphocytes
• active immunity


  defence against pathogen by antibody production in body
• active immunity is gained


  after an infection or vaccination
• vaccination


  pathogens infect again, higher concentration of correct antibodies produced
• vaccination


  1. weakened pathogens/antigens are put in the body

  2. antigens stimulate an immune response by lymphocytes which produce antibodies

  3. memory cells produced, long term immunity
• pathogen


  has its own antigens with specific shapes
• antibodies


  proteins that bind with antigens leading to destruction of pathogens or marking of pathogens for destruction by phagocytes
• specific antibodies


  have complementary shapes which fit specific antigens
• passive immunity


  short term defence against a pathogen by antibodies acquired from another individual
• passive immunity in infants

  1. antibodies pass from mother to infant through breast milk

  2. babies immune system not well developed

  3. antibodies from mother protect it from diseases (mum is immune)
• cholera


  diseases caused by bacterium transmitter in contaminated water
• cholera


  1. cholera bacteria attach to wall of small intestine

  2. produce a toxin

  3. causes secretion of chloride ions into small intestine

  4. osmotic movement of water into the gut

  5. causing diarrhoea, dehydration and loss of ions from blood