1. The Immune System

2. 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.

3. 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

4. Different pathogens cause common infectious diseases

5. 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

6. Direct contact requires touching an infected individual.
Includes:
Kissing
Sexual intercourse
Hand shaking
tick

7. 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.

8. 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.

10. 3 types of proteins fight off invading pathogens
Complement proteins weaken pathogen membranes.
Antibodies make pathogens ineffective.
Interferons prevent viruses from infecting healthy cells.
antibody
pathogens

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12. 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 a specific immune response.
Having chicken pox
Acquired Immunity occurs after given a vaccine.
Flu shot

13. 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

14. 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 carries genes for antibiotic resistance on a plasmid.
A copy of the plasmid is transferred through conjugation.
Resistance is quickly spread through many bacteria.

15. Vaccines artificially produce acquired immunity
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.

16. How a vaccination provides immunity
Antigens in a vaccine trigger an immune response, and memory B cells are made. 1
memory B cells
Stimulates a specific immune response
Causes memory cells to be produced
A memory B cell is stimulated when the real pathogen binds to it. 2
Allows immune system to respond quickly to infection
The B cell quickly activates and makes antibodies that fight the pathogens before you get sick. 3
Has a fast response, a person will not get sick