Fighting Disease
Pathogen
• An organism that causes diseases
• All infectious diseases are caused by
pathogens
• When you have an infectious disease a
pathogens have gotten inside your body
and caused harm
4 major pathogens
1. Bacteria-damage cells by producing a
toxin (tetanus, strep throat)
2. Viruses- destroy cells as they reproduce
inside (flu, colds)
3. Fungi- athletes foot, ringworm
4. Protists- malaria, African Sleeping
Sickness, dysentery.
Spread of Pathogens
- Infected people- directly (kissing) or
indirectly (sneezing, coughing)
- Soil, food, water- contagen in the food,
soil, or water
- Contaminated object- indirect contact
- Infected animals- ticks, mosquitoes,
raccoons, etc (biting a person)
The Body’s Defenses
• Skin is first line of defense
• Breathing passages have cilia
• Mouth and stomach have chemicals to
destroy pathogens
Immune system response
• White blood cells- phagocyte (engulfs
pathogen)
• Inflammation- Increases blood flow to
infected area (white blood cells)
• Fever- Pathogens can’t grow at higher
temperatures
• TCells- distinguishes one pathogen from
another
Immune system cont..
• B Cells- Produce proteins that help
destroy pathogens (antibody)
• Antibodies bind to the pathogen and stop it
from making you sick
AIDS
• Caused by the virus HIV
• Attacks T cells and shuts down the
immune system
• Body loses ability to fight disease
• Spread by body fluids- not shaking hands,
hugging, toilet seat etc…
Immunity
• Active- bodies response to presence of
pathogens.
- result of getting the disease or a
vaccine
• Passive- Antibodies come from another
source other than body (immunity passed
from mother to baby at birth)
Cancer
• Non-infectious
• Cells multiply uncontrollably
• Carcinogen- cancer causing agent (tar in
cigarette, uv radiation in sunlight)
Vaccination
• Antibodies and memory cells form
• When real pathogen enters the body the
memory cells help produce antibodies to
fight it
Antibiotic
• Slows growth or kills bacteria
• Totally ineffective against viruses
Vector
• Carries the disease but does not actually
have the disease (ticks, mosquitoes)
Carrier
• Has the disease but shows no sign of the
disease (some people carry strep throat
but never have any symptoms)
• Are still contagious even without
symptoms