immune system

• what are some natural body defences?

  • skin
  • hair and mucus
  • hydrochloric acid
• lymphocytes produce antibodies or antitoxins, which attach to and kill pathogens
• antibiotics dont kill viruses because viruses live inside cells
• phagocytes engulf pathogens
• memory cells recognise pathogens on reinfection
• what are some physical plant defences?

  • waxy cuticle
  • cell walls
• what are some chemical plant defences?

  • production of antibacterial chemicals
  • production of poisons that deter herbivores
• what are some mechanical defences of plants?

  • thorns or hairs
  • mimicking other organisms
• what are symptoms of plant diseases?

  • stunted growth
  • spots on leaves
  • patches of decay
  • discolouration
• drugs are trialled to test for:

  • dose
  • toxicity
  • efficacy
• in a double blind trial the patients are split into two different groups, one is given the placebo and one the actual drug, neither patients or doctors know which is which
• Skin is a tough, dry outer layer of the body that acts as a physical barrier to pathogens. Skin also has sebum or oil on the surface that repels pathogens. Scabs also form over cuts which involve platelets which also forms a barrier to pathogens.
• Eyes produce tears which are antiseptic and contain enzymes to kill bacteria.
• The trachea, bronchi and nose produce mucus, which is sticky. This traps bacteria and is carried away by cilia.
• Antitoxins neutralise toxins produced by pathogens. Memory cells can also be formed which give a ore rapid response if the pathogen re-enters the body.