Lecture 17 BIO 311D 1st Edition Outline of Last Lecture I Blood Components II Partial Pressure Gradients in Gas Exchange III Respiratory Surfaces IV How other animals breathe V Lungs VI Pathway of the Respiratory System VII Control of Breathing in Humans Outline of Current Lecture I Hemoglobin II Carbon Dioxide Transport III Respiratory Adaptations IV The Immune System VI Barrier Defenses VII Inflammatory Responses Current Lecture Hemoglobin A single hemoglobin molecule can carry four molecules of O2 one molecule for each iron containing heme group Higher affinity for carbon dioxide and carbon monoxide The hemoglobin dissociation curve shows that a small change in the partial pressure of oxygen can result in a large change in delivery of O2 CO2 produced during cellular respiration lowers blood pH and decreases the affinity of hemoglobin for O2 this is called the Bohr shif Carbon Dioxide Transport Hemoglobin also helps transport CO2 and assists in buffering the blood CO2 from respiring cells diffuses into the blood and is transported in blood plasma bound to hemoglobin or as bicarbonate ions HCO3 Fully oxygenated hemoglobin arriving in capillaries near active muscles where PO2 is about 40 mm Hg would likely unload of its O2 at that point A 10 B 30 C 50 D 70 E 90 Respiratory Adaptations of Diving Mammals Diving mammals have evolutionary adaptations that allow them to perform extraordinary feats For example Weddell seals in Antarctica can remain underwater for 20 minutes to an hour For example elephant seals can dive to 1 500 m and remain underwater for 2 hours These animals have a high blood to body volume ratio Deep diving air breathers stockpile O2 and deplete it slowly Diving mammals can store oxygen in their muscles in myoglobin proteins Diving mammals also conserve oxygen by Changing their buoyancy to glide passively Decreasing blood supply to muscles Deriving ATP in muscles from fermentation once oxygen is depleted Innate immunity is present A Only in mammals B Only in vertebrates C Only in animals D In eukaryotes but not in prokaryotes E In all three domains of life including eubacteria and Achaea The Immune System Innate immunity is present before any exposure to pathogens and is effective from the time of birth It involves nonspecific responses to pathogens Innate immunity consists of external barriers plus internal cellular and chemical defenses Adaptive immunity or acquired immunity develops after exposure to agents such as microbes toxins or other foreign substances It involves a very specific response to pathogens In innate immunity recognition and response rely on traits common to groups of pathogens Innate immunity is found in all animals and plants In vertebrates innate immunity is a first response to infections and also serves as the foundation of adaptive immunity In insects an exoskeleton made of chitin forms the first barrier to pathogens The digestive system is protected by a chitin based barrier and lysozyme an enzyme that breaks down bacterial cell walls Hemocytes circulate within hemolymph and carry out phagocytosis the ingestion and digestion of foreign substances including bacteria Hemocytes also secrete antimicrobial peptides that disrupt the plasma membranes of fungi and bacteria Innate Immunity of Invertebrates The immune system recognizes bacteria and fungi by structures on their cell walls An immune response varies with the class of pathogen encountered The immune system of mammals is the best understood of the vertebrates Innate defenses include barrier defenses phagocytosis antimicrobial peptides Additional defenses are unique to vertebrates natural killer cells interferons and the inflammatory response Barrier Defenses Barrier defenses include the skin and mucous membranes of the respiratory urinary and reproductive tracts Mucus traps and allows for the removal of microbes Many body fluids including saliva mucus and tears are hostile to many microbes The low pH of skin and the digestive system prevents growth of many bacteria Pathogens entering the mammalian body are subject to phagocytosis Phagocytic cells recognize groups of pathogens by TLRs Toll like receptors A white blood cell engulfs a microbe then fuses with a lysosome to destroy the microbe There are different types of phagocytic cells Neutrophils engulf and destroy pathogens Macrophages are found throughout the body Dendritic cells stimulate development of adaptive immunity Eosinophils discharge destructive enzymes Cellular innate defenses in vertebrates also involve natural killer cells These circulate through the body and detect abnormal cells They release chemicals leading to cell death inhibiting the spread of virally infected or cancerous cells Many cellular innate defenses involve the lymphatic system Antimicrobial Peptides and Proteins Peptides and proteins function in innate defense by attacking pathogens or impeding their reproduction Interferon proteins provide innate defense interfering with viruses and helping activate macrophages About 30 proteins make up the complement system which causes lysis of invading cells and helps trigger inflammation Inflammatory Responses The inflammatory response such as pain and swelling is brought about by molecules released upon injury of infection Mast cells a type of connective tissue release histamine which triggers blood vessels to dilate and become more permeable Activated macrophages and neutrophils release cytokines signaling molecules that enhance the immune response Pus a fluid rich in white blood cells dead pathogens and cell debris from damaged tissues Inflammation can be either local or systemic throughout the body Fever is a systemic inflammatory response triggered by pyrogens released by macrophages and by toxins from pathogens Septic shock is a life threatening condition caused by an overwhelming inflammatory response Evasion of Innate Immunity by Pathogens Some pathogens avoid destruction by modifying their surface to prevent recognition or by resisting breakdown following phagocytosis Tuberculosis TB is one such disease and kills more than a million people a year
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