Biology · Ch 7 — Human Health and Disease
Summary
Summary
- Health and its dimensions: Health is a state of complete physical, mental and social well-being, not merely the absence of disease. It is influenced by genetics, lifestyle, infections, and the environment.
- Pathogens and diseases: Common infectious agents include bacteria (Salmonella → typhoid), viruses (Rhinovirus → common cold, HIV → AIDS), protozoans (Plasmodium → malaria, Entamoeba histolytica → amoebiasis), and helminths (Wuchereria bancrofti → filariasis). Each has a specific mode of transmission (air, water, vector, sexual contact).
- Immunity types: Innate immunity is non-specific, present from birth (four barriers: physical, physiological, cellular, cytokine). Acquired immunity is pathogen-specific, develops after exposure, and has memory (humoral via B-cells/antibodies; cell-mediated via T-cells).
- Antibody structure and classes: Antibodies (immunoglobulins) are Y-shaped proteins with two heavy and two light chains. Five classes exist — IgG (most abundant, secondary response), IgA (mucosal), IgM (first response), IgE (allergy), IgD (B-cell receptor).
- Vaccination and immune memory: Vaccines contain weakened/inactivated pathogens or antigens, triggering primary response and memory cells. On re-exposure, a faster, stronger secondary response (anamnestic) prevents disease.
- Allergies and autoimmunity: Allergies are hypersensitive reactions to harmless allergens (e.g., pollen), mediated by IgE and mast cells. Autoimmune diseases (e.g., rheumatoid arthritis, Type 1 diabetes) occur when the immune system attacks self-tissues.
- AIDS — causative agent and mechanism: HIV (a retrovirus) targets helper T-cells (CD4+), reducing their count and causing immunodeficiency. Transmission: sexual contact, blood, infected needles, mother-to-child. Diagnosis via ELISA/Western blot; treatment uses antiretroviral therapy (ART), not a cure.
- Cancer — types and causes: Neoplasms can be benign (localised) or malignant (invasive, metastatic). Carcinogens include chemicals (tobacco smoke), radiation (UV, X-rays), and oncogenic viruses carrying viral oncogenes. Cellular oncogenes (proto-oncogenes), present in normal cells, can also be activated to drive oncogenic transformation.
- Cancer detection and therapy: Diagnosis via biopsy, histopathology, imaging (CT, MRI, mammography), and tumour markers. Treatment: surgery, radiotherapy, chemotherapy, immunotherapy (e.g., monoclonal antibodies, interferons).
- Drugs and alcohol abuse: Common drugs of abuse include opioids (morphine, heroin), cannabinoids (marijuana), cocaine, and hallucinogens (LSD). Alcohol abuse leads to liver cirrhosis, brain damage, and addiction. Dependence is both psychological and physical. …