1.1.1 VACCINATIONS involve injecting small amounts of DEAD or INACTIVE microorganisms.
these carry ANTIGENS which cause your body to produce ANTIBODIES to attack them -
even though the microorganisms is HARMLESS (since its dead or inactive). for example, the
MMR vaccine contains WEAKENED versions of the viruses that causes MEASLES, MUMPS
and RUBELLA (german measles) all in one vaccine.
1.1.2 when your infected with a new MICROORGANISM, it takes your white blood cells a few
days to LEARN how to deal with it. but by that time, you can be pretty ILL
1.1.3 but if live microorganisms of the same type appear
after that, the white blood cells can RAPIDLY
mass-produce antibodies to kill of the pathogen.
1.1.4 some vaccinations "wear off" over time. so BOOSTER injections may nee to be given to
increase levels of antibodies again
1.2.1 vaccines don't always work - sometimes they DONT give you
1.2.2 you can sometimes have a BAD REACTION to a vaccine (e.g. swelling, or maybe
something more serious like a fever or seizures). but bad reactions are very RARE
1.3.1 vaccines have helped CONTROL lots of infectious diseases that were once COMMON in the UK (e.g. polio,
measles, whooping cough, rubella, mumps, tetanus...). SMALLPOX no longer occurs at all, and POLIO infections
have fallen by 99%.
1.3.2 big outbreaks of disease - called EPIDEMICS - can be prevented if
a LARGE PERCENTAGE of the population is vaccinated. that way,
even the people who aren't vaccinated are UNLIKELY to catch the
disease because there are FEWER people able to pass it on. but if a
significant number of people ARENT vaccinated, the disease can
SPREAD quickly through them and lots of people will be ILL at the
2.1 some drugs just RELIVE SYMPTOMS - others CURE the problem
2.1.1 PAINKILLERS (e.g. aspirin) are drugs that relive pain. however, they don't actually
tackle the CAUSE of the disease, they just help to reduce the SYMPTOMS
2.1.2 other drugs do a similar kind of thing - reduce the symptoms without
tackling the underlying CAUSE, for example, lots of "cold remedies"
don't actually CURE colds.
2.1.3 ANTIBIOTICS (e.g. penicillin) work differently - they actually KILL (or prevent growth of) the
bacteria causing the problem without killing your own body cells. DIFFERENT ANTIBIOTICS
kill DIFFERENT TYPES of bacteria, so its important to be treated with the right one.
2.1.4 but antibiotics DON DESTROY VIRUSES (e.g. FLU or COLD viruses).
viruses reproduce USING YOUR OWN BODY CELLS, which makes it very
difficult to develop drugs that destroy just the virus without killing the body's
2.2 BACTERIA can become RESISTANT to ANTIBIOTICS
2.2.1 bacteria can MUTATATE - sometimes the mutations cause them to be RESISTANT to
(not killed by) an ANTIBIOTIC
2.2.2 if you have an INFECTION, some of the bacteria might be resistant to antibiotics
2.2.3 this mans that when you TREAT the infection, only the NON-RESISTANT strains of bacteria will be killed.
2.2.4 the individual RESISTANT bacteria will SURRIVE and REPRODUCE. and the population of the
resistant strain will INCREASE. this is an example of natural selection.
3 microorganisms that enter the
body are called pathogens
3.1 pathogens cause INFECTIOUS DISEASES
3.2 there are TWO MAIN TYPES of
PATHOGEN:BACTERIA and VIRUSES
18.104.22.168 are very small LIVING CELLS which
can reproduce rapidly inside your body
22.214.171.124 they make you FEEL ILL by doing TWO
things: a)DAMAGING YOUR CELLS,
b)PRODUCING TOXINS (poisons)
126.96.36.199 are NOT cells-they're much smaller
188.8.131.52 they REPLICATEBTHEMSELVES by invading YOUR
CELLS and using the cells' MACHINERY to produce
many COPIES of themselves. the cell will usually
then BURST, realising all the new viruses.
184.108.40.206 this CELL DAMAGE is what
makes you feel ill
4 Defence System
4.1 your SKIN, plus HAIRS an
MUCUS in your respiratory tract
(breathing pipework), stop a lot of
nasties getting inside your body
4.2 to try and prevent microorganisms getting into the body through
CUTS, small fragments of cells (called PLATELETS) help blood
clot quickly to seal wounds. if the blood contains LOW NUMBERS
of platelets it will CLOT MORE SLOWLY.
4.3 but if something does make it through, your IMMUNE SYSTEM kicks in. the
most important part is the WHITE BLOOD CELLS. they travel around in your
blood and crawl into every part of you, constantly patrolling for microbes.
when they come across an invading microbe they have three lines of attack.
4.3.1 1.CONSUMING them
220.127.116.11 white blood cells can ENGLUF
foreign cells and DIGEST them
4.3.2 2.producing ANTIBODIES
18.104.22.168 every invading cell has unique molecules (called
ANTIGENS) on its surface.
22.214.171.124 antibodies are then produced RAPIDLY and carried around the
body to kill all similar bacteria or viruses.
126.96.36.199 when your white blood cells come across a FOREIGN ANTIGEN (i.e. one they don't recognise), they
will start to produce PROTEINS called ANTIBODIES to lock onto and kill he invading cells. the
antibodies produced are specific to that type of antigen - they wont lock on to any others.
188.8.131.52 if the person is infected with the same pathogen again the white blood
cells will rapidly produce the antibodies to kill it - the person is
NATURALLY immune to that pathogen and wont get ill
4.3.3 3.producing ANTITOXINS
184.108.40.206 these counteract toxins produced by the INVADING BACTERIA