Section 3.3. Maintaining Healthy Systems

Section 3.3
Maintaining Healthy Systems
The Enemies of our Immune System
 Pathogens are harmful organisms that can invade
the body and cause disease.
Includes viruses, bacteria, parasites, and fungi
(pox virus)
E.g. Bacteria - Cholera
E.g. Fungi – Athletes Foot (Tinea pedis)
E.g. Parasite – Common roundworm (Ascaris
Our Body’s Immune System
 Innate Immune System
1st immune response (within
Phagocytes in the body attack
the parasites at the site of
They recognize pathogens by
identifying their antigens and
then engulf the parasites.
Antigens are proteins that are located
on the surface of a pathogen (each
pathogen has a unique antigen)
 Adaptive Immune System
2nd immune response (days to
weeks after parasite enters)
The adaptive immune system
produces antibodies which will
attack the pathogens
They will also form memory cells to
protect the body from the same
Vaccinations – E.g. Virus
 A vaccine for the flu is
composed of antigens from
the influenza virus.
 The body will then produce
antibodies that are specific
to the influenza virus.
If the flu virus infects an
individual after the flu shot,
their body will have a stronger
immune response
therefore killing the virus.
Vaccine Controversy - Pros
 If used widespread, the vaccine can eliminate a
harmful pathogen
E.g. smallpox virus
E.g. rubella virus (German measles)
 Vaccines allow the human body to prepare for
infection in a manner that is more safe than being
exposed to the pathogen without vaccination.
Vaccination Controversy - Cons
 Vaccines tend to produce side effects.
 The side effects vary between vaccine but range from:
Redness, swelling, itching, bruising, headache, nausea, severe allergic reactions,
tiredness, vomiting, seizure, fevers, coma & brain damage (rare),
 Vaccines are expensive to produce
The Canadian government spent 2 billion in vaccines against H1N1
 Vaccinations can be dangerous for children
 Vaccines may accelerate the rate of pathogen evolution
Super bugs
The Community Immunity Dilemna
 If a small percentage of the population receives a
vaccination, then the virus (or other pathogen) will
be able to survive and harm many people.
All the individuals who took the vaccine were susceptible to the
side effects.
 If a large percentage of the population receives a
vaccination, then everyone is protected. Even
those that did not receive the vaccination.
Independent Reading – Stopping the Spread of
Disease (page 112-114)
 Read pages 112-114
 Answer questions 5-8 (page 115)
Thursday Work Activity 3-C
 Read pages 119-120
 Answer all questions on page 120
 Include a title page

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