Human Health and Disease

Health is a state of complete physical, mental and social well-being, and it is affected by genetic disorders, infections and lifestyle. In this chapter you will study common human diseases and their pathogens: typhoid caused by Salmonella typhi and confirmed by the Widal test, pneumonia caused by Streptococcus pneumoniae and Haemophilus influenzae, the common cold caused by rhinoviruses, malaria caused by Plasmodium and spread by the female Anopheles mosquito, amoebiasis caused by Entamoeba histolytica, ascariasis, filariasis caused by Wuchereria, and ringworm caused by fungi such as Microsporum and Trichophyton. You will then learn how the body defends itself through innate and acquired immunity, the structure of an antibody (H2L2), humoral and cell-mediated responses, active and passive immunity, vaccination, allergies and autoimmunity, and the primary and secondary lymphoid organs. The chapter also explains how HIV destroys helper T lymphocytes to cause AIDS, how cancer cells lose contact inhibition, and how cancer is detected and treated. Finally, it discusses drug and alcohol abuse in adolescence, including opioids, cannabinoids and coca alkaloids, and their prevention.

Detailed Worksheet: Human Health and Disease Section A - Definitions (10 marks) 1. Define health. List any two factors that affect human health. (2 marks) 2. Distinguish between innate immunity and acquired immunity. (2 marks) 3. What are interferons? To which category of innate immunity barriers do they belong? (2 marks) 4. Distinguish between benign and malignant tumours. What is metastasis? (2 marks) 5. What is an allergen? Name the antibody and the chemicals released from mast cells during an allergic reaction. (2 marks) Section B - Calculations and Applications (15 marks) 6. An antibody molecule consists of two heavy chains and two light chains. If each heavy chain has about 440 amino acids and each light chain about 214 amino acids, calculate the total number of amino acids in one antibody molecule. Write the notation used to represent this structure. (3 marks) 7. A survey of 2,000 children in a district found 160 cases of amoebiasis, 240 of ascariasis and 40 of typhoid. Calculate the percentage incidence of each. Identify the common route of transmission for these diseases and suggest two public health measures. (3 marks) 8. A person's primary immune response produced a low level of antibody that peaked after about 10 days, while a second exposure to the same antigen produced a peak ten times higher within 4 days. If the primary peak was 50 units, calculate the secondary peak. Explain why the secondary response is faster and stronger. (3 marks) 9. Match each disease with its pathogen and mode of transmission: malaria, filariasis, common cold, ringworm, pneumonia, typhoid. (3 marks) 10. A mother is advised to breastfeed her newborn during the first few days. Name the fluid secreted, the antibody it is rich in, and the type of immunity it provides. Classify these as natural or artificial, active or passive: (i) recovery from measles (ii) tetanus antitoxin injection (iii) polio vaccine. (3 marks) Section C - Diagrams (10 marks) 11. Draw a labelled diagram showing the stages in the life cycle of Plasmodium in the human body and in the female Anopheles mosquito, indicating sporozoites, liver stage, RBC stage, gametocytes and the site of fertilisation. (4 marks) 12. Draw a labelled diagram of the structure of an antibody molecule showing heavy chains, light chains, antigen-binding sites and disulphide bonds. (3 marks) 13. Draw a labelled flowchart showing the replication of HIV in a host cell, from entry into a macrophage to the formation of new viruses. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. A person with malaria suffers high fever and chills that recur every three to four days. Explain the cause of these symptoms in terms of the Plasmodium life cycle, name the toxin involved, and analyse why controlling Anopheles mosquitoes is the most effective preventive measure. (5 marks) 15. Explain why the number of helper T lymphocytes falls progressively in a person infected with HIV, and why such a person becomes susceptible to infections like Mycobacterium and Toxoplasma. Evaluate why there is no complete cure for AIDS, and suggest preventive measures. (5 marks) 16. An adolescent begins smoking and drinking under peer pressure. Analyse the short-term and long-term effects of alcohol and tobacco on the body, explain the difference between drug abuse and dependence, and suggest four measures that parents and schools can take for prevention. (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Draw all diagrams neatly in pencil and label every part. Use scientific names of pathogens correctly.