Transcript B2 – Keeping Healthy

B2 – Keeping Healthy
Natural Barriers to Microorganisms
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Skin
Chemicals in tears
Sweat
Stomach acid
In suitable conditions (such as inside the body)
microorganisms can reproduce rapidly.
Infectious Diseases
• Microorganisms may enter the body and cause illness
before the immune system can destroy them.
• Symptoms of a disease are caused by:
– Damage done to cells by the microorganisms
– Poisons (toxins) they produce
White Blood Cells
• Our immune system defends against the invading
microorganisms
• White Blood Cells can destroy microorganisms by:
– engulfing and digesting them
– by producing antibodies
Antibodies
• A different antibody is needed to recognise each different
type of microorganism
• Once the body has made the antibody to recognise a
particular microorganism, it can make that antibody
again very quickly, therefore protecting against that
particular microorganism.
Vaccinations
• Vaccinations provide protection from
microorganisms by establishing antibodies
before infection
• Vaccination contains a usually safe form of
a disease-causing microorganism
Herd Immunity
• To prevent epidemics of infectious diseases, it is
necessary to vaccinate a high percentage of a
population
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http://www.immunisation.nhs.uk/About_Immunisation/Science/Herd_immunity_-_animation
Whose Choice?
• Vaccination can never be completely safe,
since individuals have varying degrees of
side effects from a vaccine
• Conflict between a person’s right to choose
and what will benefit the society as a whole
Influenza (Flu) & HIV
• New vaccines against Flu need to be
developed regularly as the virus changes
quickly
• Difficult to develop a vaccine against HIV
because this virus damages the immune
system and has a high mutation rate
Antibiotics
• Kills bacteria and fungi, but not viruses
• Over time may become resistant to antibiotics
• Random changes (mutations) in the genes of
microorganisms sometimes lead to varieties which are
less affected by the antibiotic
Reduce Antibiotic Resistance
• Only use antibiotics when necessary. Not
when you have the flu or common cold as
these are viruses.
• Always complete the full course of antibiotics.
Drug Testing
• First tests for safety and
effectiveness involve:
– Human cells grown in lab
– Animals
• Second tests are carried out
with humans:
– On healthy volunteers to test
for safety
– On people with the illness to
test for safety and
effectiveness
• Blind Trial: Patients do not know which
group they are in
• Double Blind Trial: Patients and Doctors do
not know who is in each group
http://www.youtube.com/watch?v=aSP2OMiFxhg&feature=PlayList&p=06CAD7DA2E77F66F&playnext=1&playnext_from=PL&index=32
Placebo
– A “fake” drug that does nothing. Eg: a
sugar (glucose) tablet.
– Compares the new drug to see if it
does any better than nothing.
– Patients don’t know which pill they
have taken though
– Placebos are not commonly used in
Human trials as they are unethical
Arteries
• Thick outer wall. Thick layers of muscles and
elastic fibres. Artery carry blood to the body
from the heart. Blood under high pressure.
Veins
• Thin outer wall. Thin
layers of muscle
and elastic fibres.
Carry blood from
the body back to the
heart. Blood is low
pressure
• Requires it’s own
blood supply to
deliver oxygen
and nutrients and
to take away
waste products
from heart cells.
• If blood vessels
supplying the
heart become
blocked by fatty
deposits it can
cause a heart
attack.
Heart
Heart Disease
• Caused by lifestyle and/or genetic factors.
Not microorganisms.
• Eg: Poor diet, stress, cigarette smoking,
excessive alcohol intake
Heart Disease
• More common in the
UK than nonindustrialised
countries
• Regular moderate
exercise reduces
the risk of
developing heart
disease