Chapter 36 Defense against disease Mechanisms of Defense against disease Microbes bacteria protists fungi viruses When microbes cause disease they re pathogens Vertebrates have 3 major lines of defense Nonspecific external barriers prevents most disease o Two surfaces Mucous membranes of the digestive reparatory urogenital tracts Skin dead cells filled with tough proteins Sweat and sebaceous glands secrete natural antibiotics lactic acid Antimicrobial secretions mucus and ciliary action o Mucous membrane secretions trap microbes o Lysozyme kills bacteria by digesting their cell walls o Cilia sweep of mucus if swallowed they are killed in stomach acid urine inhibits bacterial growth Nonspecific internal defenses innate immunity o White blood cells leukocytes or phagocytes engulf foreign particles or infected cells and murders viciously 3 important phagocytes travel though blood steam patrol body eliminate macrophages neutrophils dendritic cells natural killer cells kill body s own cells that have become invaded or cancerous Kills any nonself cell major histocompatibility complex MHC o Inflammation recruits leukocytes phagocytes seals of injured area Promotes clotting Begins when damaged cells release chemicals causing mast cells to release histamine Initiates protective behavior by causing pain Histamine relaxes smooth muscle capillary walls become leaky Other chemicals are also released by mast cells initiate blood clotting o Fever Combats large scale infections Combats large scale infections Endogenous pyrogen released by macrophages travels to hypothalamus and raises body temp slows microbial reproduction and enhances bodies fighting abilities stimulates cells to produce interferon makes surrounding non infected cells more resistant to infection Specific internal defenses final line of defense particular organism o Adaptive immune response immune cells selectively destroy specific invading microbes and toxins and then remember the invader Allows rapid response if it reappears in the future 3 major components immune cells o macrophages and dendric cells o B cells stems cells completing their development in cone marrow o T cells migrate from marrow to thymus tissues and organs immune cells are produced and reside in the following o lymphatic system lymph extracellular fluid flows through lymph nodes contain masses of macrophages and lymphocytes o thymus gland beneath breastbone essential in development of some immune cells o spleen abdomen filters blood kills pathogens and aged red blood cells secreted proteins adaptive immune responses include three steps lymphocytes recognize an invading microbe and distinguish it launch attack retain memory of invader Adaptive immune system recognition system recognize complex molecules antigens antibody generating lymphocytes generate antibodies and T cell receptors recognize and bind to antigens o antibodies produced by B cells can be receptors binders or effectors killers Y shaped made of two peptide chains one heavy one small Consist of a constant region similar to all antibodies and variable region that different among individual antibodies Variable regions form sites that bind antigens Multiple modes of action Bind to pathogen and neutralize it Coat surface of pathogens to make it easier for phagocytic cells to destroy Interact with complement proteins in blood o Punch holes in plasma membranes o Promote phagocytosis o T cell receptor produced by T cell Recognize invaders and trigger immune response T cell receptors are never released into blood steam and don t contribute to destruction of invading microbes or toxic molecules Launches two types of attacks Binds to antigen o Humoral immunity provided by B cells and antibodies that they secrete into the blood that attack pathogens outside the body s cell large Antibodies found on only a few B cells bind to antigens Only binded cells divide rapidly Daughter cells differentiate into two cell types Memory B cells play important role in figure immunity to invader Plasma cells produce high quantity of specific antibodies in blood stream o Cell mediated immunity produced by cytotoxic T cell that kills cell and any pathogens inside it Cytotoxic T cell receptors bind to viral cancer protein punch holes in it Helper T cells enhance cell mediated immune response Impossible without them Bind to proteins on surfaces of dendritic cells or full macrophages Stimulates production of more B and cytotoxic T cells 1 2 weeks to mount a strong immune response after first exposure to invading microbe HIV kills helper T cells Adaptive Immune memory Antibiotics vaccines Cells differentiate to memory B and T cells Antibiotics Chemicals that combat infection by slowing down multiplication Vaccines stimulate development of memory cells o Mostly weakened or killed microbes of some pathogens antigens 40 of U S citizens get cancer Chapter 37 Endocrine System Methods of communication between cells fall into four broad categories Direct tissues such as heart muscle has gap junctions that directly link the insides of adjacent cells o Allows ions and electrical signal to flow between them o Very fast but short range Synaptic used in nervous system o Signal travels very quickly between other nerve cells o Synapse where nerve cell communicates with a target Communicates by releasing chemicals neurotransmitters Paracrine o Cells release chemicals to other cells in the immediate vicinity o Only influence a small group of close cells o Paracrine hormones Prostaglandins modified fatty acid hormones that contribute to inflammation and Aspirins relieve symptoms by blocking enzymes that synthesize prostaglandins pain sensations Endocrine hormones o Released through bloodstream o Move throughout body in seconds o Triggers responses that last from seconds to lifetime o 3 classes of endocrine hormones peptide chains of amino acids consists of hypothalamus pituitary parathyroid panceas thymus kidney heart fat digestive track amino acid derived composed to one or two modified amino acids steroid synthesized from cholesterol lipid soluble bind to receptors inside target cells diffuse through plasma membrane of target cells hormone receptor complex binds to DNA and affects protein synthesis o hormones act by binding receptors on or in target cells receptors found in two locations on target cells plasma membrane inside the cell within cytoplasm or nucleus o peptide and amino acid hormones usually bind to receptors on the surface of
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