germ theory germ theory proposes that microorganisms cause diseases (not spirits, as once believed)....
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The Immune System
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Germ Theory• Germ theory proposes that microorganisms cause diseases (not spirits, as
once believed).– Proposed by Louis Pasteur
– Led to rapid advances in understanding disease• Supported by Koch’s postulates.– Disease-causing agents, or particles, are called pathogens.
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There are different types of pathogens • Bacteria are single-celled organisms:
– Cause illness by destroying cells, release toxic chemicals
– Ex: Food poisoning, MRSA
• Viruses are genetic material surrounded by a protein coat:
– Force host cells to make more viruses, small– Ex: Flu, Cold, HIV
• Fungi can be multicellular or single-celled:– Take nutrients from host cells by piercing healthy cells– Occur in warm and damp places – Ex: Athlete’s foot
• Protozoa are single-celled organisms.– Use host cells to complete their life cycles– Take nutrients from host cell– Ex: Malaria
Review: Parasite
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Different pathogens cause common infectious diseases
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Pathogens can enter the body in different ways
• Pathogens can be transferred by indirect or direct contact.• Indirect contact does not require touching an infected
individual. – Touching an infected
surface– Breathing in infected
air
• Vectors :Carry a pathogen and transmit into healthy cells– Ex: Insects (ticks, mosquitoes, fleas), food
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• Direct contact requires touching an infected individual. – Includes:
• Kissing• Sexual intercourse • Hand shaking
tick
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Many body systems protect you from pathogens
• The immune system is the body system that fights off infection and pathogens.
• Many other tissues and systems help the immune system.– Skin is the (first) physical barrier to infection.– Mucous membranes trap pathogens entering the body.– The circulatory system transports immune cells.
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Cells and proteins fight the body’s infections• White blood cells attack infections inside
the body.– Phagocytes engulf and destroy
pathogens. – T cells destroy infected cells.– B cells produce antibodies, which
deactivate the pathogen.
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antibody
pathogens
3 types of proteins fight off invading pathogens
– Complement proteins weaken pathogen membranes.
– Antibodies make pathogens ineffective. – Interferons prevent viruses from infecting
healthy cells.
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Immunity prevents a person from getting sick from a pathogen
• In all types of immunity, pathogens are destroyed before you get sick.– Passive immunity occurs without
an immune response.• Mother’s milk• Genetics
– Active immunity occurs after aspecific immune response.• Having chicken pox
– Acquired Immunity occurs after given a vaccine.• Flu shot
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Artificial methods are used to control pathogens
Antibiotics and antiseptics cause pathogens to burst
• Antiseptics kill pathogens outside of the body– Do not target specific
pathogens– Ex: Vinegar, Soap, Rubbing
Alcohol, Purel
• Antibiotics kill pathogens inside the body.– Target one specific bacterium
or fungus– NOT effective against viruses
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Antibiotic Resistance• Overuse and misuse of antibiotics can cause medicines to
become ineffective.– Some bacteria in a population have genes that make them
immune to antibiotics.– These bacteria spread the gene, making the antibiotics
useless.A bacterium carriesgenes for antibioticresistance on a plasmid.
A copy of the plasmid is transferredthrough conjugation.
Resistance is quicklyspread throughmany bacteria.
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• Vaccines control pathogens and disease– Injected with antibodies that have been exposed to the
pathogen. • Gives instant but short- term protection.
– Given mild or dead version of the pathogen. • Your body makes the antigens itself for long-term protection.• Memory B cells stay for a long time, ready for another attack from the
same organism.
Vaccines artificially produce acquired immunity
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– Stimulates a specific immune response
– Allows immune system to respond quickly to infection
– Causes memory cells to be produced
– Has a fast response, a person will not get sick
A memory B cell isstimulated when the real pathogen binds to it.
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The B cell quickly activates and makes antibodies that fight the pathogens before you get sick.
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Antigens in a vaccinetrigger an immune response, and memory B cells are made.
1memory B cells
How a vaccination provides immunity