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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 Some carried by wind, water, direct contact, indirect contact… Some carried by vectors • Vector: object that carries a pathogen • Examples: 1) Malaria – mosquitos carry the protozoan 2) Black Death – carried by flea’s of mice 3) West Nile Virus – carried by birds, but spread by mosquitos 1st line of defense: physical barrier Oils & sweat destroy some pathogens • Some cells burst • Some cells shrivel Coat the openings of the body Nose, mouth, ears, eyes, genitals, anus Lined with cilia & sticky fluids to trap pathogens Job: Search & destroy Phagocytes: surround & engulf invaders • Phagocytosis Lymphocytes: • T cells: destroy infected body cells • B cells: Inactivate invaders Blood stream Complimentary Proteins • Weaken cell membrane • Attract phagocytes • Cause microbes to stick to wall of blood vessel Antibodies • Proteins made by B cells • Attach to antigens found on surface of cells • How they help: 1) Bind to antigens of pathogen (like handcuffs) Causes pathogens to clump Easy targets for phagocytes 2) Weakens the cell membrane of pathogen Causes them to burst B CELLS MAKE ANTIBODIES ANTIBODIES ATTACH TO ANTIGENS OF THE PATHOGEN Y Y Y Y Y Y YY YY Y Y Blood Stream Y Y Y Y Y Y Y phagocyte Y Y Y ANTIBODIES CAUSE THE PATHOGENS TO CLUMP TOGETHER PHAGOCYTE DESTROYS PATHOGENS Y Defense Proteins • Interferon – Cell becomes infected by virus – Infected cell releases interferon to neighbors – Healthy cell (right) absorbs the interferon and creates defense enzymes – Healthy cell able to fight virus virus Virus RNA New virus New virus New virus New virus Interferon proteins New virus Vaccination • Prevents infections (not a cure) • Vaccination process – Weakened pathogen is injected – Antigens of pathogen cause your immune system to attack • Immune system response: – Production of memory cells (for future infections) – Antibodies bind to antigens (for current infection) • Goal: Speed up immune response if you encounter the actual virus