Download 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
1700’s
E.g.
Smallpox
(pox virus)
E.g. Bacteria - Cholera
E.g. Fungi – Athletes Foot (Tinea pedis)
E.g. Parasite – Common roundworm (Ascaris
lumbricodois)
Our Body’s Immune System
 Innate Immune System

1st immune response (within
hours)

Phagocytes in the body attack
the parasites at the site of
infection.

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
pathogen
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