a. Personal Health Health refers to a person s physical, mental and social condition. Good health is determined by physiology, environment, lifestyle and the provision of healthcare services. Healthy lifestyles include balanced diet and nutrition, regular exercise, adequate rest and good personal hygiene. s How often do you do physical exercise? Do you think it is adequate? When do you usually go to bed? Is it scientific to say that one will age faster if he/she stays late at night? Compare the average life span of people living in developed and developing countries. Suggest reasons to explain the phenomena. Compare the major causes of death in 1950s and 2000s in Hong Kong. What is the meaning of health according to the World Health Organisation? How do diet, exercise and rest affect our health? What are the long term effects of smoking on our body? What are the health hazards posed by alcohol and drug abuse? What types of diseases may possibly be caused by poor personal hygiene? 1
b. Diseases Infectious Diseases Some diseases are infectious. They are caused by pathogenic agents such as viruses, bacteria, fungi, protoctists, worms and insects. There are different ways of transmission of an infectious disease. Some infectious diseases can be transmitted from the host to another individual by direct contact. Others are transmitted through water, air, droplets, food, body fluids, excretion or vectors (e.g. insects). Diseases caused by bacterial infection can be cured by antibiotics. Indiscriminate use of antibiotics would lead to the development of drug-resistant bacteria. s Comment on the saying Wearing masks is the most effective method to stop the spread of SARS. in 2003? Why does the government suggest us not to feed wild pigeons and birds? How was antibiotic first discovered? Why do we need to finish a full course of antibiotic treatment? What are the causative agents of infectious diseases in humans? Suggest ways by which infectious diseases are transmitted. Give examples on each case. How can the spread of diseases be reduced in the light of their ways of transmission? Explain the action of antibiotics on treating infections or diseases caused by bacteria. How is the development of antibiotic-resistant bacteria related to the indiscriminate use of antibiotics? 2
Non-infectious Diseases Distinguish between infectious and non-infectious diseases. What is allergy? What causes allergy? How do we distinguish a malignant tumour from a benign one? Illustrate with an example how the incidencee of a type of cancer is related to certain lifestyles. Give some examples of cardiovascular diseases. Briefly describee how these heart diseases develop. Is there any casual relationship between the incidencee of cardiovascular diseases and certain lifestyles? Is diabetes always caused by uncontrolled diets? If not, what are the causes of other diabetic cases? For non-insulin-dependent diabetic patients, suggest how the disease can be controlled through managing their lifestyles. Outline the biological principles in the control of insulin-dependent diabetes. Non-infectious diseases refer to diseases that are not caused by pathogens. Allergies, some cancers, cardiovascular diseases and diabetes are some common non-infectious diseases. The causes of these diseases are complex and multifactorial. These diseasess can be due to dietary deficiency, degeneration of body tissues, an inherited defected gene, social conditions, or lifestyles. What is the top killer disease in Hong Kong? Activities Search the website of the Centre for Health Protection of Department of Health and find information on some common infectious and non-infectious diseases in Hong Kong. Survey on the allergic cases in the class. What are the most common forms of allergy in the class and what are the allergens? 3
Prevention of Diseases Key Idea Infectious diseases can be prevented by vaccination. Immunisation programme, healthy lifestyle and improving community health are essential to disease prevention. Comment on the saying Eating health supplements can promote health. Activity Check for the information on the types of vaccination that you have ever received since birth. Compare and contrast the risk factors of coronary heart disease and diabetes mellitus. How could we adjust our lifestyles to reduce the chance of developing these diseases? How does our government help in the prevention of diseases in the society? How can you help in preventing disease transmission in our society? c. Body Defence Mechanism Our bodies have a variety of mechanisms to protect ourselves against diseases. There are non-specific and specific defence mechanisms. Skin and mucous membranes lining our body surfaces act as physical barriers to the entry of pathogens, while secretions such as tears, saliva and gastric juice, are chemical barriers which kill different pathogens. Upon invasion by pathogens or damage to tissues, our body would respond by producing inflammatory responses, blood clotting and phagocytosis. Phagocytosis is carried out by white blood cells called phagocytes which engulf foreign particles, pathogens and dead cells. These are the non-specific defence mechanisms of our body. 4
Humoral and cell-mediated immune responses are our body s specific defence mechanisms. These responses act against specific pathogens, foreign cells, or abnormal body cells. Lymphocytes contribute to acquired immunity and there are antigen receptors on their cell surfaces to bind with specific antigens. There are two types of lymphocytes: B lymphocytes (B cells) and T lymphocytes (T cells). B lymphocytes are involved in humoral immune response, which involves the production of antibodies in response to antigens. T lymphocytes are involved in cell-mediated immune response. Secondary response to the same antigen is faster, stronger and lasts longer than the primary response. This forms the basis of vaccination. There are several ways to gain immunity against infectious diseases. Recovery from an infected disease, or injection of vaccine could provide active immunity, whereas injection or intake of antibodies could provide passive immunity. Why breast feeding is good for baby? Distinguish between non-specific and specific defence mechanisms. By what ways can pathogens get into our body? How can our body form barriers to prevent pathogens from entering it? How can our body prevent infections through cuts? How does our body respond if pathogens get into it? How do B-cells and T-cells work together to fight against a specific antigen? Compare and contrast the action of B-cells and T-cells on fighting against an antigen. Explain the biological principles on which vaccines work. What is the purpose of booster injections in vaccination? Breast-fed babies can gain immunity from their mothers. What is the difference between this type of immunity and that from vaccinations? Explain how the immune system of the body works in the rejection of transplant organ. 5