Human Health and Disease - Quick Revision
Health is a state of complete physical, mental and social well-being, not merely the absence of disease. Disease-causing organisms (bacteria, viruses, fungi, protozoans, helminths) are called pathogens.
Common diseases and pathogens
- Typhoid - Salmonella typhi (bacterium); enters small intestine via contaminated food/water, spreads via blood. Confirmed by Widal test.
- Pneumonia - Streptococcus pneumoniae and Haemophilus influenzae; infects alveoli which fill with fluid.
- Common cold - Rhino viruses; infect nose and respiratory passage but NOT lungs.
- Malaria - Plasmodium (P. vivax, P. malariae, P. falciparum); P. falciparum causes fatal malignant malaria. Vector = female Anopheles mosquito.
- Amoebiasis - Entamoeba histolytica (large intestine); houseflies are mechanical carriers.
- Ascariasis - Ascaris (round worm).
- Filariasis/elephantiasis - Wuchereria (W. bancrofti, W. malayi); lymphatic vessels; mosquito vector.
- Ringworm - fungi Microsporum, Trichophyton, Epidermophyton; dry scaly itchy lesions.
Immunity
- Innate = non-specific, present at birth (4 barriers: physical, physiological, cellular, cytokine).
- Acquired = pathogen-specific, has memory; primary (low) then secondary/anamnestic (high) response. B-lymphocytes make antibodies (H2L2); T-lymphocytes mediate CMI.
- Active immunity = host makes own antibodies (slow). Passive = ready-made antibodies given (e.g., colostrum IgA, placental, antitoxin in tetanus).
- Allergy = exaggerated IgE response; histamine/serotonin from mast cells. Autoimmunity = body attacks self (e.g., rheumatoid arthritis).
- Primary lymphoid organs: bone marrow, thymus. Secondary: spleen, lymph nodes, tonsils, Peyer's patches, appendix, MALT.
AIDS & Cancer
- AIDS - HIV (retrovirus, RNA genome); reverse transcriptase makes viral DNA; destroys helper T-cells; diagnosed by ELISA; spreads only through body fluids.
- Cancer - loss of contact inhibition; benign (confined) vs malignant (metastasis). Carcinogens: ionising/non-ionising radiation, chemicals (tobacco), oncogenic viruses; proto-oncogenes.
Drugs & Alcohol
- Opioids (heroin from Papaver somniferum, depressant), cannabinoids (Cannabis sativa, affect cardiovascular system), coca alkaloids (cocaine from Erythroxylum coca, stimulant, blocks dopamine transport). Addiction (psychological) and dependence (withdrawal syndrome).