Disease: Bacteria and Viruses

Disease Contagious diseases are caused by pathogens: Pathogen- any disease-causing agent, especially bacteria and viruses

Immune Response 3 lines of defense against pathogens: Skin- acts as barrier Injured cells send chemical signal- increases blood flow to injured area T Cells/B Cells- weapon that destroys a specific pathogen

Human Immune System

T Cells A type of lymphocyte (or WBC) Main source of immunity 2 types: “helper” and “killer” Helper T Cell- recognizes virus infected cell, sends signal Killer T Cell- binds to infected cell and destroys it

B Cells Another type of lymphocyte Makes antibodies against pathogens Antibody- recognize antigens on surface of cell, bind to it, and destroy it

Antibodies recognize antigens Antigen- foreign substance on surface of cell that triggers an immune response (attack it!) When you fight off a disease, you develop antibodies against it to prevent getting disease again Also get antibodies from mother’s milk

Different types of Immunity Active Immunity- immune response triggered by your own body from actively having disease (usually life-long immunity) Passive Immunity- antibodies passed from mother’s milk to child’s body (usually not permanent but protects child for some time)

What is a bacteria? Bacteria- prokaryotic cell (no organelles) Unicellular Spherical, spiral, or rod shaped Reproduces asexually (fission)-identical copy

Common Diseases Caused by Bacteria: Streptococcus (Strep Throat) Conjunctivitis (Pink Eye) Lyme Disease (from infected Tick bites) Anthrax

What is a Virus? Virus- strand of DNA enclosed in a protein capsule that causes disease Non-living! Can only replicate in body of its host Has ability to mutate into different strains (Iike influenza and different flu shots)

Virus Structure DNA enclosed in capsid (protein coat)

Common Diseases Caused by virus: HIV (virus that causes AIDS) Influenza (the common flu) Smallpox (pretty much eradicated now)

Vaccinations Vaccines- injection of weakened or dead virus that triggers production of antibodies Increases immunity to a viral disease

Antibiotics Antibiotic- substance or compound that kills, or inhibits the growth of bacteria Ex. Penicillin Question: Should your doctor prescribe you an antibiotic for the common flu?

Protect Yourself!!! Protect Yourself! (List of ways to avoid common pathogens)