Download How do we fight disease?

How do we fight
disease?
Immune System
Pathogens
• Microorganisms that make us sick are
called pathogens
• Diseases caused by pathogens are called
infectious diseases
Types of pathogens
• Bacteria
– example: strep, tetanus
• Viruses:
– colds, flu
• Fungi:
– athlete’s foot & ringworm
• Protists:
– amoebic dysentery
How are pathogens spread?
A. Contact with an infected person
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•
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1. Direct contact: kissing, shaking hands
2. Indirect contact: sneezes
B. Contaminated food, water & soil
C. Contaminated objects
D. Infected animals
Body Defenses
• Barriers (First Line of Defense)
– 1. Skin
– 2. Breathing passages
• Mucus
• Cilia
– 3. Mouth & stomach
• Saliva
• Stomach acid
If something gets through the
barriers:
• Invaders cause damage to cells which trigger
an inflammatory response (Second Line
of Defense)
– Fluid & white blood cells leak into tissues to
fight the pathogens
– Phagocyte- engulfs pathogens and digests them
– Fever- higher temperature kills pathogens
Immune System (3rd Line of
Defense)
• If pathogen is bad enough for a fever, then
the 3rd line of defense is triggered, the immune
response
• Immune system has cells to target specific
pathogens
Immune System Cells
• T-Cells- identify the pathogens
• B-Cells- produce antibodies in response to
the antigens on the pathogen to fight each
different type of pathogen
• Go to p. 571 sketch the diagram in your book
explaining how the T cells and the B cells
fight off infection. (yes, I want you to copy
the exact diagram and labels)
Preventing Infection
• Immunity: the bodies ability to destroy
pathogens before the cause the disease
• Two types:
– Active
– Passive
Active Immunity
• your own body produces antibodies in
response to the presence of a pathogen
– When you get sick and the T & B cells fight off
the pathogen, the remember it, if it comes back
they are ready (chicken pox)
– OR
– Vaccination- when you are vaccinated some of
the disease is injected into you to trigger an
immune response
Passive immunity
• When antibodies to fight disease come from
some place other than your own body
– Example: babies get antibodies through breast
milk & from mothers blood before birth