Human Health and Disease — Short Notes
Health (WHO): state of complete physical, mental, and social well-being, not merely absence of disease.
Common Diseases in Humans
Bacterial
| Disease | Causative agent | Symptoms |
|---|---|---|
| Typhoid | Salmonella typhi | High fever, weakness, headache; Widal test for diagnosis |
| Pneumonia | Streptococcus pneumoniae, Haemophilus influenzae | Fluid in alveoli → breathing difficulty |
Viral
| Disease | Agent | Notes |
|---|---|---|
| Common cold | Rhinoviruses | Nasal congestion, sneezing |
| Dengue | Dengue virus | Fever, joint pain; via Aedes mosquito |
| Chikungunya | Chikungunya virus | Similar to dengue |
Protozoan
| Disease | Agent | Vector |
|---|---|---|
| Malaria | Plasmodium (falciparum most dangerous) | Female Anopheles mosquito |
| Amoebiasis | Entamoeba histolytica | Contaminated food/water |
Fungal
- Ringworm — Microsporum, Trichophyton, Epidermophyton — dry, scaly lesions.
Helminth
- Ascariasis — Ascaris (roundworm) — internal bleeding, muscular pain.
- Elephantiasis (Filariasis) — Wuchereria bancrofti / W. malayi; transmitted by Culex mosquito.
Malaria Life Cycle (must know)
- Bite by female Anopheles → sporozoites enter blood → liver (multiply) → RBC invasion → produces haemozoin toxin → causes chill & fever every 3–4 days.
- In mosquito gut: gametocytes fuse → sporozoites form → migrate to salivary glands.
Prevention Rules
Personal hygiene, clean surroundings, vaccinations, no mosquito breeding, safe water, sanitation.
Immunity
Innate (non-specific)
- Physical barriers — skin, mucous membranes.
- Physiological — HCl in stomach, tears, saliva.
- Cellular — neutrophils, monocytes, macrophages, NK cells.
- Cytokine barriers — interferons.
Acquired (specific)
- Antibody-mediated (humoral) — B cells produce antibodies (5 types: IgA, IgD, IgE, IgG, IgM).
- Cell-mediated — T cells (helper, killer, suppressor).
Types
- Active — body produces its own antibodies (infection or vaccination).
- Passive — ready-made antibodies given (colostrum IgA, anti-tetanus serum).
Antibody Structure
- Y-shaped, 4 polypeptides: 2 heavy + 2 light chains — represented as H₂L₂.
- Variable region binds antigen.
Vaccination
- Introduces killed/attenuated pathogen or antigenic proteins → memory cells form → quick response later.
- Recombinant vaccines — e.g. Hepatitis B vaccine.
Allergies
- Overreaction of immune system to allergens (dust, mite, pollen).
- Mediated by IgE and mast cells → release histamine & serotonin → symptoms (sneezing, watery eyes).
- Anti-histamines, steroids treat symptoms.
Autoimmunity
Immune system attacks self — e.g. rheumatoid arthritis.
Human Immune System Components
Lymphoid organs — primary: bone marrow, thymus; secondary: spleen, lymph nodes, tonsils, MALT.
AIDS (Acquired Immuno Deficiency Syndrome)
- Cause: HIV (Human Immunodeficiency Virus) — retrovirus with RNA + reverse transcriptase.
- Transmission: sexual, blood transfusion, sharing needles, infected mother to child.
- Not spread by: casual contact, sharing food, hugging, mosquitoes.
- HIV infects helper T (CD4) cells → replicates → depletes them → immune collapse.
- Diagnosis: ELISA (detects antibodies).
- Treatment: anti-retroviral drugs; not curable.
Cancer
- Uncontrolled cell division; contact inhibition is lost.
- Benign (localised) vs Malignant (invasive, metastasis).
- Causes: physical (X-ray, UV), chemical carcinogens (tobacco), biological (oncogenic viruses, e.g. HPV).
- Proto-oncogenes → oncogenes.
- Detection: biopsy, X-ray, CT, MRI, radioactive antibodies.
- Treatment: surgery, radiation, chemotherapy, immunotherapy (α-interferons).
Drugs and Alcohol Abuse
Common drugs
- Opioids (heroin, smack) — from Papaver somniferum — depressants.
- Cannabinoids (marijuana, hashish, charas) — from Cannabis sativa — affect brain.
- Cocaine (coke, crack) — from Erythroxylum coca — stimulant.
Consequences
- Loss of appetite, insomnia, mood swings, damage to liver/nervous system, addiction, financial/social ruin.
Prevention & control
- Avoid peer pressure, education, seek professional help, parental care.
Take-aways
- Disease results from pathogen entry, poor hygiene, or lifestyle.
- Immunity works at multiple layers — innate + acquired, cellular + humoral.
- HIV → AIDS; cancer → uncontrolled growth. Both stem from loss of normal cellular controls.
- Substance abuse damages physiology and psychology; awareness & counselling are key.