Transcript Immune System: Bacteria & Viruses How They Infect and Cause

Immune System:
Bacteria & Viruses
How They Infect and Cause
Disease
Page 134
Pathogens
“Sickness-Makers!”
Disease-causing agent
Germ Theory of Disease
The idea that
infectious diseases
are caused by
microorganisms, or
germs
Koch’s Postulates
series of guidelines
used to identify the
microorganism that
causes a specific
disease
Koch’s Continued
1.
The pathogen NEEDS to be found in the Sick Patient
(and should not be found in a healthy one)
2.
The pathogen MUST be isolated and grown in the lab in pure
culture.
3.
When the cultured pathogens are placed in a new host, they
should cause the same disease.
4.
The injected pathogen should be isolated from the 2nd host. It
should be identical to the original pathogen.
Why are these rules important? Because identifying pathogens
that cause disease is the first step toward preventing or curing the
symptoms they produce.
Agents of Disease
1.
2.
3.
4.
5.
Viruses
Bacteria
Protists
Worms
Fungi
Virus
They invade and replicate
w/in living cells.
They 1.) attach to the
surface of a cell,2.) insert
their DNA, and 3.)take
over many of the
functions of the host cell
(e.g.; the common cold,
influenza, smallpox, and warts)
Bacteria
Bacteria cause disease
by breaking down the
tissues of the infected
organism for food or by
releasing toxins that harm
the body
(e.g.; streptococcus infections,
diphtheria, botulism, and
anthrax)
Most bacteria are harmless to humans
Protists
Protists live in the
bloodstreams of
vertebrate animals &
feeds off the nutrients
in the host organism's
blood.
(e.g.; Trypanosoma causes
African sleeping sickness –
found in the water, Malaria is
caused by Plasmodium –
injected by mosquitoes)
Worms
Flatworms and
roundworms are also
responsible for a number
of serious human
diseases
(e.g.; Contact worms directly
by stepping on them, eating
them out of raw meat, worms
frequently infect people
working in rice fields)
Fungi
Infects by penetrating the
outer layers of skin.
Other types of fungi infect
the mouth, the throat, and
even the fingernails and
toenails.
(e.g.; Ringworm and Athletes
Foot)
How Diseases are Spread
1. Physical Contact (coughing/ sneezing)
2. Contaminated Food or Water
3. Infected Animals
Vectors
animal that carries
disease-causing
agents from person to
person
Two types of lymphocytes
• B Lymphocytes (memory B Cells):
provide immunity against antigens and
pathogens in the bodily fluids
• T Lymphocytes (T cells): provide
defense against abnormal cells and
pathogens inside living cells
Concept Maps on page 133