Biology 1- Keeping Healthy 2

Pathogens and disease
1. Pathogens are microorganisms that cause disease
  1. Pathogens reproduce rapidly inside the human body and produce toxins
    1. This makes them hard to destroy
2. Most pathogens are either bacteria or viruses
  1. Viruses reproduce inside human cells and damage them
    1. The damage to cells makes you feel ill
  2. Viruses are much smaller than bacteria
3. Washing hands removes pathogens from them
  1. Semmelweiss was the first doctor to realise this
    1. Doctors then didn't take him seriously
Defence mechanisms
1. The body prevents most pathogens from getting into the body
  1. Through skin
  2. Through mucus
  3. Through stomach acid
2. Pathogens which enter the body can be destroyed by white blood cells
  1. White blood cells...
    1. ...ingest pathogens (digest and destroy them)
    2. ...produce antibodies which attach to particular pathogens and destroy them
    3. ...produce antitoxins to counteract the toxins that pathogens produce
    4. White blood cells are part of the immune system
      1. The immune system is a body system which recognises and destroys foreign cells or proteins such as invading pathogens
Using drugs to treat disease
1. Pain killers are medicines that relieve symptoms of a disease but don't kill the pathogen
2. Antibiotics cure bacterial diseases by killing bacteria
  1. They can't kill viruses
Growing and investigating bacteria
1. Bacteria can be grown on agar jelly
2. All the materials and equipment must be sterilised- this ensures that unwanted microorganisms do not infect the culture
3. Uncontaminated cultures can be used to investigate the effects of antibiotics and disinfectants on the bacteria
Immunity
1. Dead or inactive forms of a disease are injected into a person's body
  1. White blood cells react by producing antibodies
    1. The antibodies recognise the antigen on the pathogen
  2. This makes the person immune
    1. It prevents further infection as the body responds quickly by producing more antibodies
  3. The MMR vaccine is one of several- it prevents measles, mumps and rubella
2. Vaccines protect against bacterial and viral pathogens
Changing pathogens
1. If a pathogen changes by mutation the new strain may spread rapidly
2. Some new strains can cause epidemics and pandemics
3. Some bacteria have developed resistance to antibiotics by natural selection
  1. Random mutations of pathogens produce new strains- some strains are resistant to antibiotics
    1. Antibiotics kill individual pathogens of the non-resistant strain
      1. The resistant bacteria survive and reproduce a whole population of resistant strains- natural selection
        Antibiotics should not be used for mild infections in order to slow down the rate of development of resistant strains
How do we deal with disease?
1. Vaccination protects individuals and society from the effects of disease
2. The treatment of disease has changed as our understanding of antibiotics and immunity has increased

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