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Summary Chapter 9Overview of the Body's Defense Mechanisms-Defense mechanisms include-Barriers to entry of pathogens (disease-producing microorganisms)-Skin, Stomach acid, Tears, Vomiting-Nonspecific defense mechanisms-Phagocytosis, inflammation-Specific defense mechanisms-Immune response-Antibodies-T cellsPathogens Cause Disease -Disease-causing agents include-Living Organisms-Bacteria: unicellular prokaryotes-Fungi: unicellular and multicellular eukaryotes-Parasites: unicellular and multicellular eukaryotes-Nonliving infectious “particles”-Viruses-PrionsBacteria: Single-celled Living Organisms-Characteristics-Prokaryotic-Single-celled-Use a variety of resources for growth and reproduction-Infections-Pneumonia, tonsillitis, tuberculosis, botulism, toxic shock syndrome, syphilis, Lyme disease, etc.-Generally treated with antibioticsViruses: Tiny Infectious Agents-Extremely small, much smaller than bacteria-Living? Open to debate-Unable to reproduce outside of a host cell -No metabolic activity-Structure-Contain DNA or RNA, not both-Nucleic acid is surrounded by a protein coat-Diseases-AIDS. Hepatitis, encephalitis, rabies, influenza, colds, warts, chicken poxPrions: Infectious Proteins-Infectious proteins-Normal brain proteins that are not folded correctly-This mis-folding becomes self-propagating, filling and disabling the cell with protein debris-Resist cooking, freezing, drying-Diseases-Bovine spongiform encephalitis (BSE, “mad cow disease”)-Creutzfeldt-Jakob disease (CJD)Transmissibility, Mode of Transmission, and Virulence Determine Health Risk-Transmissibility-How easily a pathogen is passed form person to person-Mode of transmission-Respiratory, fecal-oral, body fluids-Virulence-How much damage is caused by the infection Lymphatic System Defends the Body-Functions-Maintenance of blood volume in cardiovascular system-Transport of fats and fat-soluble material from digestive system-Filtration of foreign material to defend against infectionLymphatic System: Components-Lymphatic vessels transport lymph-Lymph nodes cleanse the lymph-The spleen cleanses the blood-Thymus gland facilitates maturation of T lymphocytes-Tonsils and adenoids protect the throatKeeping Pathogens Out: The First Line of Defense-Skin, and effective deterrent-Tears and saliva – contain lysozyme (antibacterial enzyme)-Ear wax – entraps microorganisms-Mucus – entraps microorganisms-Stomach – highly acidic, inhibits microorganisms-Vagina – Slightly acidic, inhibits some microorganisms-Vomiting, urination, and defecation – remove microorganisms-Resident Bacteria – Outcompete pathogensNonspecific Defenses: Phagocytes Engulf Foreign Cells-Phagocytic cells: white blood cells that surround and engulf invading bacteria-Neutrophils, macrophages, eosinophils-Inflammation-Redness, warmth, swelling, pain-Natural killer cells: a type of lymphocyte that attacks tumor cells and virus-infected cells-Complement proteins: lyse invading bacteria-Interferons: antiviral proteins-Fever ResponseSpecific Defense Mechanisms: Third Line of defense (The Immune Response)-Characteristics-Recognizes and targets specific pathogens and foreign substances-Has “memory”- “remembers” initial exposure and responds more quickly and aggressively on subsequent exposures-Able to distinguish between-Self cells and foreign invaders-Healthy cells and abnormal (tumor) cellsSpecific Defense Mechanisms: Immune Response Targets Antigens-Antigen: any substance that triggers an immune response-Usually protein of polysaccahride on outer surface of invading cell or virus -MHC (major histocompatibility complex) proteins-Self-antigens that are on human cell surfaces enabling recognition of “self”-Enable immune system to distinguish “self” from “nonself”Specific Defense Mechanisms: Lymphocytes Are Central to Specific Defenses-B lymphocytes: Antibody-mediated immunity-Antibodies: proteins made by B lymphocytes that bind with and neutralize specific antigens-Active against viruses, bacteria, and soluble foreign molecules-T lymphocytes: Cell-mediated immunity-Directly attack foreign cells -Coordinate the immune response-Active against parasites, viruses, fungi, intracellular bacteria, cancer cells, cells with “nonself” MHCSpecific Defense Mechanisms: B cells: Antibody-Mediated Immunity-B cells activated when they recognize an antigen-Divide into two cell types-Memory Cells – store information for future immune responses-Plasma Cells – actively secrete antibodies, which will bind to antigenT Cells: Cell-Mediated Immunity-T cells-Originate from stem cells in the bone marrow-Mature in the thymus-Types of T cells-CD4 T cells-Helper T cells and Memory T cells-CD8 T cells-Cytotoxic T cells and Suppressor T cells-T cells must be presented with antigen by antigen-presenting cells (APCs)-APCs include-Macrophages-B cells-Helper T cells-Secrete cytokines, which stimulate other immune system cells-Play a key role in directing the immune response-Are target of HIV infection-Cytotoxic T cells-Directly attack and destroy abnormal (tumor or viral-infected) cells and foreign cells-Memory T cells-Reactivate during later exposuresImmune Memory Creates Immunity-Primary immune response-Occurs on first exposure to antigen -Characteristics-Lag time of 3-6 days fro antibody production-Peak at 10-12 days-Secondary immune response-Occurs on second and subsequent exposure to antigen -Characteristics-Lag time in hours -Peak in daysMedical Assistance in the War Against Pathogens: Immunization-A strategy for causing the body to develop immunity to a specific pathogen-Active immunization-Intentionally expose individual to a form of the antigen that doesn't produce disease -Also known as vaccination-Passive immunization-Administer protective antibodies to an individualMedical Assistance in the War Against Pathogens: Monoclonal Antibodies-Specific antibodies produced in the laboratory by a hybrid B cell clone-Commercial applications of monoclonal antibodies-Home pregnancy tests -Prostate cancer screening test-Diagnostic testing for hepatitis, influenza, HIVMedical Assistance in the War Against Pathogens: Antibiotics Combat Bacteria-Antibiotics kill bacteria or inhibit their growth-Antibiotics are selectively toxic for bacteria by targeting features of bacterial cells that are different form eukaryotic cells-Antibiotics are not effective against virusesTissue Rejection: A Medical Challenge-Tissue rejection – May occur following tissue or organ


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OHIO BIOS 1030 - Summary Chapter 9

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