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Chapter 43 THE BODY’S DEFENSE I. Innate Immunity-Nonspecific mechanisms provide general barriers to infection A. The skin and mucous membranes (Barrier defenses) pH 3-5 Lysozymes B. Phagocytic white cells and natural killer cells (Internal defenses) Neutrophils - become phagocytic Monocytes - become macrophages Macrophages - large amoeboid cells use pseudopodia Eosinophils - use cytoplasmic granules to attack outer covering of large invaders Natural killer cells - destroys body’s own infected cells C. Antimicrobial proteins two nonspecific protein groups (Internal defenses) Complement system - 30 proteins interact which results in lysis of invading microbes (Internal defenses) Interferons - secreted by infected cells to produce proteins that inhibit viral replication D. The inflammatory response (Internal defenses) 1. Localized inflammatory response Dilated vessels become more permeable Chemical signals 2. Chemical signals Histamine released from Basophils and Mast cells Prostaglandins released from white blood cells Neutrophils arrive first kill microbe and then die Macrophages destroy pathogens and clean up II. The immune system defends the body against specific invaders A. Key features of the immune system (Adaptive Immunity) Specificity - recognize and eliminate specific microorganisms Antigen Antibody Diversity responds to numerous kinds of invaders which are recognized by their antigenic markers Memory - recognize previous antigens Self/nonself recognition B. Active versus passive acquired immunity C. Humoral immunity and cell-mediated immunity Humoral produces antibodies to free bacteria, viruses and toxins Cell-mediated response of lymphocytes to intracellular parasites D. Cells of the Immune System (lymphocytes) Early B and T cells develop from multipotent stem cells B cells mature in bone marrow and are responsible for humoral immunity T cells migrate to thymus gland and are responsible for cell-mediated response 2 Concentrated in lymph glands, spleen and other lymphatic glands Effector cells Activated B cells produce plasma cells to produce antibodies Activated T cells produce two types Helper T cells Cytotoxic T cells III. Clonal selection of lymphocytes is the cellular basis for immunological specificity and diversity IV. Memory cells in secondary immune response 3 V. Molecular markers on cell surface function in self/nonself recognition MHC = Major Histocompatibility Complex - contains glycoproteins VI. In the humoral response, B cells defend against pathogens in body fluids by generating specific antibodies A. Activation of B cells (two steps) 1. Antigen attaches to specific receptor on B cells 2. B cell activation involves macrophages and helper T cells to produce plasma cells B. T-dependent and T-independent antigens C. Molecular basis of antigen-antibody specificity Epitope = antigen’s surface recognized by antibody Comprised a specific class of proteins called immunoglobulins Y shaped molecule comprised of four polypeptide chains D. How antibodies work 4 E. Monoclonal antibodies are defense proteins that descend from a single cell VII. Cell mediated response; T cells defend against intracellular pathogens A. Activation of T cells T cells respond only to antigenic epitopes displayed on the surfaces of the body’s own cells The presence of a T cell surface molecule called CD4 enhances the interactions between the cells and antigen presenting cells (APC) The MHC-antigen complex displayed on the infected body cell stimulates T cells with the proper receptor to multiply and form clones of activated TH and TC cells which recognized the pathogen 5 The cells stimulate B cells to make antibodies The cells activate other T cell for cell-mediated response B. How cytotoxic cells work Cytotoxic cells TC actually destroy infected host cells Releases perforin which is a protein that form lesions in the infected cells membrane Cytotoxic cells also function to destroy cancer cells which develop periodically in the body VIII. Complement proteins participate in both nonspecific and specific defenses 30 or so complement proteins circulate in the blood and these proteins become activated in a series fashion IX. The immune system can distinguish between self and nonself A. Blood groups B. Tissue grafts and other organ transplants X. Abnormal immune function leads to disease A. Autoimmune diseases react against itself Lupus Erythematosus Rheumatoid Arthritis Diabetes Heart valve damage from strep infections 6 Grave’s Disease B. Allergy C. Immunodeficiency deficient in either humoral or cell mediated immune defense D. Acquired immunodeficiency syndrome (AIDS) E. Cancer and Immunity 7 Controlling The Internal Environment Chapter 44 I. Homeostatic mechanisms protect an animal’s internal environment II. Cells require a balance between water uptake and loss A. Osmoconformers and osmoregulators Osmoconformers = animals that do not actively adjust their osmolarity Osmoregulators = animals that regulate internal osmolarity by discharging excess water or taking in additional water B. Maintaining water balance different environments Most marine invertebrates are osmoconformers Marine bony fish are hypotonic to seawater Freshwater animals are hypertonic to their environment and constantly take in water by osmosis Terrestrial animals live in a dehydrating environment that cannot survive desiccation III. Osmoregulation depends on transport epithelia IV. Tubular systems function in osmoregulation and excretion in many invertebrates A. Protonephridia: the flame-bulb system of flatworms B. Metanephridia of earthworms C. Malpighian tubules of insects 8 V. The kidneys of most vertebrates are compact organs with many excretory tubules A. The mammalian excretory system Blood enters each kidney via the renal artery and exits the renal vein Urine exits each kidney through a ureter and both ureters drain into a common urinary bladder Urine leaves the body from the urinary bladder though the urethra B. The nephron and associated structures (functional unit of kidney) Water, salts, urea and other small molecules are separated from the blood passing through the glomerulus by blood pressure The filtrate enters the Bowman’s Capsule Filtrate then passes through the proximal tubule, the Loop of Henle, and the distal tubule, which empties into a collecting tubule VI. The kidneys transport epithelia regulate the composition of blood 9 A. Production of urine from blood filtrate 1. Filtration of blood 2. Secretion adds plasma at proximal and distal tubules 3. Reabsorption of sugar, vitamins, organic materials B. Transport properties of the nephron and collecting duct 1. Proximal tubules alters volume and composition of filtrate 2. Descending Loop of Henle is freely permeable to water but not salts 3. Ascending Loop of Henle is very permeable to salts but not to water 4. Distal tubule regulates K+, NaCl and pH 5. The collecting duct carries filtrate back through the medulla into the renal pelvis VII. The water-conserving ability of the kidney is a key terrestrial adaptation A. Conservation of water by two solute concentrations B. Regulation of kidney function by feedback circuits Antidiuretic hormone Juxtaglomerular apparatus Atrial Natriuretic Factor VIII. Diverse adaptations of the vertebrate kidney have evolved in different environments 10 IX. An animal’s nitrogenous wastes are correlated with its phylogeny and habitat X. Thermoregulation maintains body temperature within a range conducive to metabolism Conduction Convection Radiation Evaporation XI. Ectotherms derive body heat mainly from their surroundings and endotherms derive it mainly from metabolism XII. Thermoregulation involves physiological and behavioral adjustments 1. Adjusting the rate of heat exchange between the animal and its surrounding Vasodilation Countercurrent Heat Exchanger 11 2. Cooling by evaporative heat loss 3. Behavioral responses 4. Changing the rate of metabolic heat production XIII. Comparative physiology reveals diverse mechanisms of thermoregulation A. Invertebrates B. Amphibians and reptiles C. Fishes D. Mammals and birds Rate of heat may be increased Contraction of muscles Hormones increase the production of heat instead of ATP Cooling the body by vasodilation, panting, and sweat glands E. Thermoregulation in humans Hypothalamus controls thermoregulation F. Torpor = metabolism decreases and the heart and respiratory system slow down G. Acclimatization = temperature range adjustment XIV. Roles of liver in homeostasis 12