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B2: Keeping Healthy Answers
1. Human body barriers to stop harmful MOs getting inside:
Chemicals in tears destroy microorganisms
Your skin produces chemicals that make it hard for microorganisms to grow
If microorganisms get in through your mouth, acid in the stomach destroys most of them
The skin is a physical barrier to microorganisms
2. Microorganisms: Invade the body and cause infections. They are viruses, bacteria and fungi. When disease MOs get
inside your body, they reproduce very quickly and this causes symptoms. In warm, moist and nutritious conditions, such
as inside the body, these MOs can produce very rapidly.
3. Bacteria: living cells that can multiply rapidly in favourable conditions. Once inside the body, they release poisons or
toxins that can make us feel ill.
Viruses: only reproduce inside host cells, damaging them when they do so. Once inside, they take over the cell and make
hundreds of thousands of copies of themselves. Eventually, the virus copies fill the whole host cell and it bursts open. The
viruses then pass out through the bloodstream, the airways, or by other routes. It is difficult to develop drugs that kill
viruses without damaging the body's tissues.
4. Symptoms are caused by:
Damage done to your cells when the MOs reproduce
Poisons made by the MOs
5. Immune System: The part of the body that fights infections and destroys the invading MOs. White blood cells are an
important part of your immune system.
6. The Functions of White Blood Cells:
Engulf and digest pathogens and destroy them (phagocytosis)
Produce antibodies to destroy pathogens
Produce antitoxins that neutralise the toxins released by pathogens
7. Antibodies: A group of proteins made by white blood cells to fight dangerous microorganisms. A different antibody is
needed to fight each type of microorganism. Antibodies bind to the surface of the microorganism, which triggers other
white blood cells to digest them. Once the body has made the antibody, it can make that antibody again very quickly,
therefore protecting it against that particular microorganism. However, the microorganisms may enter the body and cause
illness before the immune system can destroy them.
8. Antibiotics: Chemicals that kill or stop the growth of bacteria and fungi, but not viruses. However, they can kill of both
`good' and harmful bacteria, which can allow harmful fungi, like thrush, to grow. Over a period of time bacteria and fungi
may become resistant to antibiotics because random mutations in the genes of these microorganisms sometimes lead
to new strains which are less affected by the antibiotic so they can reproduce and pass on their resistance.
9. Vaccines can contain:
Live pathogens treated to make them harmless
Harmless fragments of the pathogen
Toxins produced by pathogens
10. Vaccines: Act as antigens. When injected into the body, they stimulate the production of white blood cells to produce
antibodies to fight the pathogen. If the person later becomes infected with the pathogen, the required lymphocytes are
able to reproduce rapidly and destroy it.
11. The vaccine contains only a weakened or harmless version of a pathogen, which means that the vaccinated person is in
no danger of developing the disease. Some people, however, may suffer a mild reaction.
12. Sometimes vaccine boosters are required because the immune response `memory' weakens over time. Anti-tetanus
injections may need to be repeated every ten years, for example.
13. Vaccinations can never be completely safe because side-effect levels vary. So, when making a decision, these are some
of the factors that should be considered:
When fewer people are vaccinated, the number of cases of the disease increases.
The chance of falling seriously ill or dying from the disease may be far greater than the chance of experiencing a
Using a vaccine may be much cheaper than treating a very ill person.
How high the risk of infection is.
The people who are most at risk from the illness
If the vaccination is safe
14. People may refuse to have a vaccination because:
It may conflict with religious/ personal beliefs
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Society gives us the right to choose
Some people may be more prone to side effects.
15. To stop a large outbreak of a disease, almost everyone must be vaccinated because if they are not large numbers of the
disease causing MOs will be left in infected people. If the vaccination rate drops just a little, lots of people will get ill.
16. Some common diseases like influenza (flu) and the common cold are caused by viruses.…read more
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Arteries: Thick, muscular and elasticated wall means that it can strongly pump blood through the body. Narrower lumen
increases blood pressure so blood can flow much faster, which means that respiration can happen quicker.
Veins: Thinner wall and wider lumen because there is a lower blood pressure as no need to reach the heart quickly.
28. Fat can build up in the coronary arteries. A blood clot can form on the fatty lump.…read more