04 22 2014 Chapter 36 Defenses Against Diseases Understand the three major lines of defense against disease that vertebrates have and be able to give examples of each Microbes include bacteria protists and fungi and viruses o When microbes cause disease they are called pathogens Vertebrate animals have three major lines of defense against disease o Nonspecific external barriers o Nonspecific internal defenses o Specific internal defenses Nonspecific external barriers o Prevent most pathogens from entering the body o Includes skin and cilia and secretions such as tears saliva and mucus Nonspecific internal defenses o If the external barriers are breached a variety of nonspecific internal defenses swing into action o Include White blood cells which engulf foreign particles or destroy infected cells Chemicals released by damaged cells and proteins released by white blood cells that trigger inflammation and fever These operate regardless of the nature of the invader neutralizing the threat Specific internal defenses o The final line of defense is the adaptive immune response in which immune cells selectively destroy specific invading microbes and toxins and then remember the invader o This allows for rapid response to the invader if it reappears in the future Understand Table 36 2 and be able to explain the role of each of these cell types in immunity Understand how the mucous membranes are able to protect your body against microbes Antimicrobial secretion mucus and ciliary action defend the mucous membranes against microbes o Mucous membrane secretions trap microbes entering the nose or mouth o They contain antibacterial proteins including lysozyme which kills bacteria by digesting their cell walls and defensing which makes holes in bacterial plasma membranes o Cilia on the membranes sweep up the mucus so it is swallowed coughed or sneezed out of the body Understand the 3 categories of the innate immune response Innate immune responses fall into three categories o White blood cells called leukocytes or phagocytes destroy invading cells or the body s own cells if they ve been infected by viruses o The inflammatory response recruits leukocytes to the site of a wound and sets off the injured area isolating the infected tissue from the rest of the body o Fever is produced when microbes cause a major infection in the body which both slows down microbial reproduction and enhances the body s own fighting abilities Understand the role of MHC proteins in the immune response Natural killer cells are another type of leukocyte which strike primarily at the body s own cells that have become cancerous or have been invaded by viruses o The surfaces of normal body cells display proteins of the major histocompatibility complex MHC identifying the cell as self o Natural killer cells kill any nonself cells they encounter by releasing proteins that bore holes in the infected or cancerous cell s membranes and then secrete enzymes through the holes that kill the infected cell Be able to explain what happens during the inflammatory response The inflammatory response attracts phagocytes to injured or infected tissue The inflammatory response causes tissues to become warm red swollen and painful o This defense mechanism has several functions It attracts phagocytes to infected or injured tissue It promotes blood clotting It initiates protective behavior by causing pain The inflammatory response begins when damaged cells release chemicals that cause certain cells in the connective tissue called mast cells to release histamine o Histamine relaxes the smooth muscle surrounding arterioles increasing blood flow and causing capillary walls to become leaky o Extra blood flowing through leaky capillaries drives fluid from the blood and into the wounded area causing redness warmth and swelling o Other chemicals released by the wounded cells mast cells and by the microbes themselves attract macrophages neutrophils and dendritic cells o These cells consume bacteria dirt and cellular debris o In some cases pus a thick whitish mixture of dead bacteria tissue debris and white blood cells may accumulate Other chemicals released by injured cells initiate blood clotting to reduce blood loss and prevent more microbes from entering the blood stream Understand how fever is initiated and what role it plays in the immune response Fever combats large scale infections o The human thermostat located in the hypothalamus of the brain is set at 97 99 F o During an infection macrophages release a protein called endogenous pyrogen that travels to the hypothalamus and raises the thermostat s set point o Elevated body temperature increases phagocytic activity and slows bacterial reproduction Fever also stimulates virus infected cells to produce a protein called interferon which makes surrounding non infected cells more resistant to infection o In an experiment volunteers were infected with a virus and given aspirin to reduce fever or a placebo o Those with aspirin had more viruses in their noses and coughed out more viruses than the controls because fevers in the controls helped reduce the viral infection Fever is NOT always a bad thing Be able to explain the roles of B cells and T cells in the adaptive immune response When the first 2 levels of defense are breached the body mounts a highly specific and coordinated adaptive immune response directed against a particular organism to destroy it and provide future protection against that microbe but no others The adaptive immune system consists of three major components immune cells tissues and organs and secreted proteins Macrophages and dendritic cells play a role in both the innate and adaptive immune responses The key cellular players in the adaptive immune response are B cells and T cells which arise from stem cells in the bone marrow o Some of the stem cells complete their development in the bone marrow becoming B for bone cells o Others migrate from the marrow to the thymus where they develop into T for thymus cells Be able to list the various tissues and organs that are part of the adaptive immune system Tissues and organs o The cells of the immune system are produced and reside in a variety of locations including the vessels of the lymphatic system the lymph nodes the thymus and the spleen o Lymph is extracellular fluid that flows through the lymph nodes which contain masses of macrophages and specialized white blood cells called lymphocytes o The thymus is a gland located beneath
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