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IB Biology notes on infection and the body's responses.

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IB BIOLOGY Notes From IB Biology HL Pearson I. What causes infectious disease? A. pathogen: an organism or virus that causes a disease 1. includes viruses, bacteria, fungi, parasitic worms etc. II. The Body's Defences Against Infection A. Non-specific Defences 1. Barriers to pathogen entry a. Skin and mucous membranes in the respiratory, digestive and urinary tracts are mechanical barriers b . cilia in upper respiratory tract sweep mucus and particles up to the throat to be swallowed c. Secretions from oil glands of the skin inhibit bacterial growth on skin d. low pH of stomach inhibits bacterial growth/kills bacteria 2. Phagocytes and Natural Killer Cells a. neutrophils are white blood cells that can leave the blood and phagocytize bacteria in connective tissue b. eosinophils are phagocytic but are mainly used to attack large animal parasites c. Natural killer cells kill virus-infected cells and tumour cells by cell-to cell contact 3. Inflammatory Response a. occurs when tissue gets damaged b. inflamed area becomes red, painful, swollen and hot c. Damaged tissue releases histamine i. along with mast cells (a type of white blood cell) causes vasodilation and increased permeability of nearby capillaries a. results in redness and increase in temperature ii. Swelling from escaped fluid and proteins occurs iii. ...read more.


Benefits of vaccination 1. total elimination of certain diseases 2. preventing epidemics/pandemics 3. decreased health care costs 4. preventing harmful side effects of disease F. Possible dangers of vaccination 1. Side effects such as soreness near the injection site, low-grade fever 2. allergic reactions to some of the vaccine's ingredients a. e.g. Some vaccines contain egg proteins, yeast proteins, antibiotics, (leftover from the production process), human serum albumin (help stabilize live virus), formaldehyde (eliminates the effects of bacterial toxins and makes viruses unable to replicate), aluminum salts (help the vaccine work better), or gelatin that may cause an allergic reaction 3. a preservative called thimerosol contains mercury and there have been concerns about its safety (in the US it "has been removed from or reduced to trace amounts in vaccines for children 6 years of age and younger with the exception of the inactivated influenza vaccine" (Iannelli, 2008)) 4. possible overload of the immune system 5. IB lists possible links to autism but... For a comprehensive list of side effects for many vaccines, try this website: http://www.cdc.gov/vaccines/vac-gen/side-effects.htm G. So...should you use vaccines? 1. Personal choice of informed individuals is the key V. Antibiotics A. antibiotic: a chemical that inhibits the growth of microorganisms, particularly bacteria 1. ...read more.


BLOOD CLOTTING (same as from Circulatory System package) A. Clotting: formation of a solid mass of platelets, red blood cells and fibrin (a protein) 1. also called coagulation 2. Fibrinogen: a protein found in blood that is the precursor of fibrin 3. Prothrombin: inactive form of thrombin found in blood a. Vitamin K is necessary for production of prothrombin 4. Serum: blood plasma without fibrinogen B. STEPS IN BLOOD CLOTTING 1. Blood vessel is damaged 2. platelets clump at the site and partially seal the leak 3. platelets and damaged tissue release prothrombin activating factor 4. prothrombin activating factor converts prothrombin to thrombin a. requires calcium ions (Ca2+) 5. thrombin acts as an enzyme that removes 2 short amino acid chains from each end of a fibrinogen molecule, making them "sticky" 6. shortened fibrinogen molecules join end to end forming long threads of fibrin 7. fibrin threads tangle themselves around the platelets that are plugging the leak 8. red blood cells are trapped in the network of fibrin and give colour to the clot 9. when repair of blood vessel initiated, the enzyme plasmin destroys fibrin network A cute video, some details are slightly different from the notes though: http://www.youtube.com/watch?v=9QVTHDM90io&feature=related C. Rewind: Thrombosis 1. thrombosis: formation of a clot in a blood vessel a. often the result of damage to the wall of a blood vessel as in atherosclerosis b. other causes are outlined below: http://www.nhs.uk/Conditions/Thrombosis/Pages/Causes. ...read more.

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