Fighting Disease

• The spread of diseases can be reduced by

  • Being hygienic
  • Destroying vectors
  • Isolating infected individuals
  • Vaccination
• The bodies defence system includes

  • Skin
  • Nose
  • Trachea and bronchi
  • Stomach
• The skin acts as a barrier to pathogens and also secretes antimicrobial substances which kill pathogens
• The nose has hair and mucus to trap particles that could contain pathogens
• The trachea and bronchi secrete mucus to trap pathogens
• The trachea and bronchi are lined with cilia (hair like structures) which waft the mucus up to the back of the throat where it can be swallowed
• The stomach produces hydrochloric acid which kills pathogens
• White blood cells help to defend against pathogens by

  • Phagocytosis
  • Antibody production
  • Antitoxin production
• If a pathogen enters the body the immune system tries to destroy the pathogen
• Phagocytosis

  • White blood cells can engulf foreign cells and digest them
• Antibodies

  • Every pathogen has unique molecules or antigens on its surface
  • When the white blood cells detect a foreign antigen they will produce proteins called antibodies rapidly to lock onto the pathogens
  • The antibodies cause the pathogens to clump together making it easier for phagocytes to engulf them
  • The person is naturally immune to this pathogen
• Antitoxins

  • White blood cells neutralise toxins produced by invading bacteria
• Vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the white blood cells to produce antibodies
• If the same pathogen re-enters the body after vaccination the white blood cells respond quickly to produce the correct antibodies, preventing infection
• Advantages of vaccination

  • Spread of pathogens can be reduced by immunising a large proportion of the population
• Disadvantages of vaccination

  • Vaccinees do not always work
  • Sometimes there may be a bad reaction to a vaccine but this is rare
• Antibiotics (such as penicillin) are medicines that help to cure bacterial disease by killing infective bacteria inside the body
• It is important that specific bacteria should be treated by specific antibiotics
• The use of antibiotics has greatly reduced deaths from infectious bacterial diseases however the emergence of strains resistant to antibiotics is of great concern
• Antibiotics cannot kill viral pathogens because viruses enter body cells
• Painkillers and other medicines are used to treat the symptoms of disease but do not kill pathogens
• It is difficult to develop drugs that kill viruses without also damaging the body’s tissues
• To slow down the rate of development of resistant strains of bacteria doctors avoid over prescribing antibiotics
• Bacteria can mutate and make resistant bacteria which can reproduce and will not be killed by antibiotics