1. The Immune System

2. Pathogens Defined: microorganisms that cause disease
Viruses: turn cells into virus making factories
Bacteria: prokaryotes that can release toxic chemicals
Fungi: pierce cells and absorb the nutrients
Protozoans: single cells protista (eukaryotes)
Parasites: grow and feed on a host

3. Pathogens (contd)
Some carried by wind, water, direct contact, indirect contact…
Some carried by vectors
Vector: object that carries a pathogen
Examples:
Malaria – mosquitos carry the protozoan
Black Death – carried by flea’s of mice
West Nile Virus – carried by birds, but spread by mosquitos

4. The Skin 1st line of defense: physical barrier
Oils & sweat destroy some pathogens
Some cells burst
Some cells shrivel

5. Mucus Membranes Coat the openings of the body
Nose, mouth, ears, eyes, genitals, anus
Lined with cilia & sticky fluids to trap pathogens

6. White Blood Cells Job: Search & destroy
Phagocytes: surround & engulf invaders
Phagocytosis
Lymphocytes:
T cells: destroy infected body cells
B cells: Inactivate invaders

9. Defense Proteins Complimentary Proteins Weaken cell membrane
Attract phagocytes
Cause microbes to stick to wall of blood vessel

10. Defense Proteins Antibodies Made by B cells
Bind to cell membrane of pathogen
Prevents pathogen from binding to host cells
Causes pathogens to clump
More susceptible to phagocytes
Weakens the cell membrane
Causes them to burst

12. Defense Proteins Interferon Produced by virus infected cells
Stimulates uninfected cells to create infection preventing enzymes

13. Vaccination Prevents infections (not a cure)
Memory cells developed without actually getting the disease
Vaccine
Contains antigens of a pathogen
Weakened pathogen is injected
Stimulates the production of memory cells
Speeds up immune response if you encounter the unweakened virus