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South Tuen Mun Government Secondary School Biology Revision Note 18 Health = a state of complete physical, mental and social well-being (World Health Organization) Disease = a condition in which any body part cannot function normally, showing symptoms. Lifestyle and health: (i) Diet Eating less deficiency symptoms e.g. deficiency of protein Kwashiorkor Eating too much Excess cholesterol / fat blocking and narrowing of coronary artery reduce transport of oxygen and nutrients to the cardiac muscle fail / weak to beat stop beating heart attack Excess cholesterol / fat blocking and narrowing of artery to the brain reduce transport of oxygen and nutrients to brain cells stop function stroke Excess sugar remains in the mouth bacteria break down the sugar to release acid acid dissolves enamel tooth decay Excess sugar / fat excess energy intake obese higher risks of heart diseases, diabetes, stroke, arthritis Excess salt higher blood pressure higher risks of heart diseases / stroke and breaking of artery (damage to the brain and kidney) (ii) Exercise Strengthen heart muscle and intercostal muscles, diaphragm better ventilation and circulation Keep bones and muscle strong and supple reduce the risks of injuries and osteoporosis Promote mental and social well being (iii) Rest allow the body and brain to recover physically and mentally better alertness, judgment, reaction time and memory + reduce the risks of depression / better mood allow growth hormone to work (iv) Personal hygiene of hair, hands, skin and mouth (oral hygiene) – reduce the chance of infection by microorganisms and the spread of diseases (v) Smoking, alcohol and drug abuse Smoking is hazardous to health: diseases associated with smoking – chronic bronchitis, emphysema, asthma, heart disease and heart attack miscarriage and premature birth in pregnant woman Alcohol: Short term effects – judgment, physical coordination blurred vision, slurred speech and loss of balance car accident death Long term effects – addiction and inflammation of liver, cirrhosis, higher blood pressure, heart disease, stroke, cancers of mouth, throat, oesophagus Drug e.g. heroin, cannabis, MDMA, Ketamine, Methylamphetamine, cough medicine abuse addiction withdrawal symptoms (e.g. nervousness, sleep problems, muscle pain) death Heroin breathing and menstrual problems, coma Cannabis, MDMA, Ketamine, Methylamphetamine, cough medicine reduced concentration, slow response Infectious diseases Pathogen Bad effects Examples Virus (non cellular, Act as a parasite of a host cell destroy Influenza, SARS, AIDS, dengue fever, not a living thing the cell membrane, stop the synthesis of nucleic acid or protein lysis of cell measles Bacteria Cholera dehydration and death Protist Acts as a parasite Malaria burst of red blood cells Fungi Acts as a parasite Athlete’s foot Worms Acts as a parasite Liver fluke inflammation of liver Acts as a parasite (food-borne disease) Production of toxins (food poisoning) Route of transmission Route Examples Preventive measures Droplets Influenza, common cold, Cover the mouth during coughing or sneezing SARS Wear surgical mask Avoid crowded places Air Measles, tuberculosis Good ventilation Contaminated water Cholera, gastroenteritis Drink clean water, distilled water, boiled water Proper disposal of faeces Contaminated food Cholera Proper handling of food Cook food thoroughly Body fluid (through wound, sharing of needle / Hepatitis B, AIDS Wear gloves when handling wounds Cover wounds with dressing Do not share needles / shaves Screen blood before blood transfusion Stay with one healthy sex partner Use condom during sex intercourse Remove the breeding ground of vectors e.g. remove or add oil to stagnant water Kill the vectors e.g. by insecticide Prevent contact with vectors e.g. wear long-sleeved clothes shaves, blood transfusion, sex intercourse,) Vector (e.g. mosquito, flies, cockroach) Cholera (flies, cockroach); Denger fever & malaria (mosquito) Direct contact Athlete’s foot, genital herpes Good personal hygiene Other preventive measures: Immunization programme + vaccination Community health – screening of infectious diseases e.g. Cervical Screening Programme; disease surveillance; health education Treatment of infectious diseases Killing bacteria by antibiotics destroy the formation of cell wall OR inhibit synthesis of nucleic acid, protein (bacteria cannot multiply or grow) / damage the cell membrane (lysis of bacteria) Killing bacteria by sulpha drugs acts as competitive inhibitors of certain enzyme in bacteria Cocktail therapy to kill HIV (virus that causes AIDS) Non infectious diseases Non infectious diseases Causes and bad effects Risk factors Allergy Overreaction of the immune system running nose, sneezing, itch, skin rash, swelling, shortness of breath, loss of consciousness, death Uncontrolled abnormal cell division in localized region (benign tumour) OR in certain region and spread to invade other regions through blood and lymph (malignant tumour) damage of tissue death Cancer Cardiovascular diseases High blood pressure / blocking and narrowing of coronary artery coronary heart disease Family history Chemical carcinogen e.g. tar in cigarette, nitrosamine in salted fish, asbestos Radiation e.g. UV light, X ray Virus e.g. HPV, Hepatitis B virus Diet (excess cholesterol, fat (trans fats, saturated fat), salt, sugar Smoking, alcohol Aging, family history, obese, diabetes, stress, lack of exercise Diabetes Family history (= inherited tendency) Allergens e.g. dust mites, pollens, animal hair, insect stings, certain food Type I (insulin-dependent): defective pancreas less insulin secretion excess blood glucose level glucose excreted in urine Family history Type II (non insulin-dependent) : body cells e.g. liver cells are insensitive to insulin excess blood glucose level glucose excreted in urine Family history Aging, obese, lack of exercise Preventive measures – to reduce the risk of non infectious disease Healthy lifestyle (balanced diet, regular exercise, enough rest, good personal hygiene, do not smoke and abuse alcohol / drugs, reduce contact of allergens and carcinogens) Disease surveillance e.g. data and mortality rate of cancers Health education (healthy lifestyle, diagnosis of non infectious disease and treatment) Non specific body defence mechanisms (i) Physical barrier (ii) Skin is made up of a layer of dead cell that forms a physical barrier to prevent the entry of pathogens. Hair in the nose forms a net to trap pathogens and prevent their entry into the respiratory tract. Mucus in the nose and trachea sticks pathogens and prevent their entry into the respiratory tract. Cilia in the trachea beats to move the sputum out of the trachea. Chemical barrier Oily secretion (sebum) by sebaceous gland of the skin can kill pathogens. Gastric juice contains hydrochloric acid that can kill most pathogens. Tear and saliva contains lysozyme that catalyses the breakdown of bacteria’s cell wall. Vaginal fluid is acidic to inhibit the growth of pathogens. (iii) (iv) Blood clotting – the formation of blood clot in the wounds, to prevent excess bleeding and the entry of pathogens Phagocytosis and inflammatory response Phagocytosis is carried out by a kind of white blood cell, called phagocytes. Phagocytosis at the wound leads to the inflammatory response Arteriole dilate more blood flows to the capillary around the wound red and hot at the wound Accumulation of tissue fluid, pathogens, phagocytes pus and swollen at the wound Swollen wound press on the pain receptors pain feeling Specific body defence mechanisms Antigens are chemical molecules (normally protein or polysaccharides) that are found on the surface of the cells. The antigens, if they are considered as “foreign” to a person, an immune response will be initiated. The cells of specific pathogen have specific antigen. The specific antigen can stimulate specific lymphocytes to respond in two different ways: humoral immune response (HIR) or cell mediated immune response (CMIR). B cells are formed and matured in the bone marrow. A pathogen has a specific antigen. Specific antigen stimulates specific B cell to respond. The specific plasma cell produces specific antibody that acts on the specific antigen. The memory cell is also specific. The specific antibody has a shape complementary to the specific antigen. It binds with the antigen leading to make a hole and the pathogen cell is lysed. [lysis] enhance phagocytosis, more pathogen cells are engulfed and killed. stick the cells of the pathogens into a clump, so the pathogen cannot reproduce. neutralize the toxins of the pathogens, so the pathogens become harmless to the body. T cells are made in bone marrow but matured in the thymus gland. The infected cells and cancer cells are specific. They stimulate specific helper T cell and specific T cell to respond. Thus the killer T cell and memory T cell are also specific. Primary response (first exposure to a pathogen) and secondary response (subsequent exposure to the same specific pathogen): The secondary response is carried out by the specific memory B cell / T cell formed after the first exposure. The secondary response has a shorter latent period, more antibody is produced at a faster rate and the higher level of antibody lasts longer duration to safe guard the body. Natural active immunity = natural secondary response of the formed memory cells after the first exposure Vaccination (artificial active immunity) – injection of vaccine that contains a specific antigen of a pathogen (cause a serious disease), the harmful effect of the antigen is already removed but it can stimulate the formation of specific memory cell. The specific memory cell can be stimulated to produce the secondary response. Types of vaccine: (i) live, weakened pathogens (e.g. measles); (ii) dead pathogens (poliomyelitis); (iii) the specific antigen chemical molecule (whooping cough); (iv) inactivated toxins of the pathogens (tetanus) Natural passive immunity = antibodies are obtained through natural processes e.g. through placenta, breast feeding Artificial passive immunity = injection of antibodies Note : active immunity can last for a longer period of time, sometimes, it can be life-long; while passive immunity is short-lifed.