Transcript The Immune System - Liberty Union High School District

The Immune System
Nonspecific and
Specific Defense
You do not need to write down anything in blue.
What is a pathogen?
•
Pathogen: disease causing agent
• Harmful to living things
Check out this slow
motion sneeze!
http://www.youtube
.com/watch?v=e2QA
GVMlns4
Examples of Pathogens include
•
Bacteria
•
Viruses
•
Parasites,
like fungi,
protists, &
worms
How are Pathogens Spread?
• Soil
• Water
• Infected animals
• Food
• Animal Bites
– This includes mosquitoes (West Nile Virus), ticks
(Lyme Disease), fleas (Bubonic plague), flies
(various infections)
• Person-to-person contact
Q: How do bacteria cause damage to host cells?
A: By releasing poisonous substances called toxins.
•
Did you know?…the Tetanus bacteria is
found in soil and one drop of the toxin,
the size of a period, can kill 30 people.
These images are of two men
undergoing an extreme muscle
spasm caused by toxins produced by
tetanus bacteria.
The Immune System
 Immune
System: body system that
fights off invading pathogens
 Two types of defense:
• Nonspecific Defense
• Specific Defense
st
1 line of
Non-Specific Defense
Skin: A physical barrier to
pathogens.
• Any break in the skin allows
entry.
• Releases sweat, oils, and
waxes that contain
chemicals toxic to bacteria.
 Mucous membranes:
Tissues that line internal body
surfaces that are in contact
with the environment.
• Mucous: Sticky fluid that
traps pathogens.

1st line of Defense:
Types of Non-specific Defense
Stomach: Has acid that
destroys potential pathogens
that are swallowed
 Phagocytes: WBC’s that
ingest (eat) pathogens
• Macrophages: Ingest and
Phagocytes and their relatives
destroy pathogens.
• Neutrophils: Ingest
pathogens, then secrete
deadly toxic chemicals to
kill them

• Short video clip on phagocytes:
http://www.youtube.com/watch?v=CEOV-SFTlpY.
Macrophage
Neutrophils
1st line of Defense:
Types of Non-specific Defense

Moderate Fevers (< 103O F):
Inhibit growth of pathogens
and recruit macrophages

Inflammation: Reaction to
tissue damage. Phagocytes
consume foreign substances.
(Symptoms: swollen, redness,
heat, pain)
Inflammation
Figure 24.2
Swelling
Pin
Skin
surface
Bacteria
Phagocytes and
fluid move
into area
Chemical
signals
Phagocytes
WBC
1
Tissue injury;
release of
chemical signals
such as
histamine.
2
Dilation and
increased leakiness
of local blood
vessels; migration
of phagocytes to the
area.
3
Phagocytes
(macrophages and
neutrophils)
consume bacteria
and cell debris;
tissue heals.
Specific Defense: The Immune System

Organs of the Immune
System:
• Bone Marrow: makes
WBC
• Thymus gland:
where T cells mature
• Lymph nodes:
contain lots of WBC
• Spleen: removes
pathogens from blood
The Immune System involves many types of
White Blood Cells (aka Leukocytes / WBCs).
Here are a few types:
B lymphocytes: Secrete antibodies.
Antibodies: Y-shaped molecules
that grab and block certain
pathogens.
T lymphocytes: Help stimulate an immune
response.
You can call
them B cells and
T cells for short!
Specific Defense: Recognizing Pathogens


Immune Response: your wbcs attack something
Antigen: anything that causes a response
Recognition:
– Lymphocytes have receptor proteins all over
them.
– Receptor proteins recognize and bind to
antigens that match the receptor.
Immune Response gets
stronger over time
Immune Response: 1st time a
certain pathogen is encountered by the
body
• After infection is fought, some B and T
cells stay alive for years as memory
cells.
• Memory cells can divide to fight
pathogens that they “remember” if they
ever meet again.
 Primary
 Secondary
Immune Response: a
later exposure to the same pathogen
• Response is faster and stronger
due to memory cells.
Draw this graph!