Chapter 8 — Human Health and Disease — covers common diseases, immunity, cancer, drugs/alcohol abuse. Carries 6-8 marks. Focus on the immune system (innate vs adaptive), AIDS, and cancer.
Key Concepts
Common Diseases
| Disease | Pathogen | Type | Symptoms | Vector |
|---|---|---|---|---|
| Malaria | Plasmodium (vivax/falciparum) | Protozoan | Recurring fever with chills | Female Anopheles mosquito |
| Amoebiasis | Entamoeba histolytica | Protozoan | Bloody stool, abdominal pain | Housefly (contaminates food) |
| Ascariasis | Ascaris lumbricoides | Helminth | Internal bleeding, anaemia | Contaminated food/water |
| Filariasis (Elephantiasis) | Wuchereria bancrofti | Helminth | Swelling of limbs | Female Culex mosquito |
| Typhoid | Salmonella typhi | Bacteria | High fever, weakness | Contaminated food/water |
| Pneumonia | Streptococcus pneumoniae | Bacteria | Fever, cough, chest pain | Droplet infection |
| Ringworm | Microsporum, Trichophyton | Fungi | Scaly lesions on skin | Direct contact |
Immunity
| Type | Description | Examples |
|---|---|---|
| Innate (Non-specific) | Born with; first line of defence | Skin, mucus, stomach acid, WBCs, interferons |
| Acquired (Adaptive) | Develops after exposure to pathogen | Antibodies, memory cells |
Acquired Immunity
| Type | Mechanism | Example |
|---|---|---|
| Active (Natural) | Body produces antibodies after infection | Getting chickenpox → lifelong immunity |
| Active (Artificial) | Vaccination → body produces antibodies | Polio vaccine, BCG |
| Passive (Natural) | Antibodies received from mother | IgA in colostrum, IgG via placenta |
| Passive (Artificial) | Pre-formed antibodies injected | Anti-tetanus serum, anti-venom |
Antibodies (Immunoglobulins)
5 types: IgG (most abundant, crosses placenta), IgA (in secretions, colostrum), IgM (first response), IgE (allergies), IgD (on B-cell surface)
HIV/AIDS
HIV = retrovirus (RNA → DNA using reverse transcriptase)
Attacks helper T-cells (CD4+) → destroys immune system
Transmission: sexual contact, blood, mother-to-child, shared needles
ELISA = screening test; Western Blot = confirmatory test
AIDS when CD4+ count drops below 200/μL → opportunistic infections
Attacks helper T-cells (CD4+) → destroys immune system
Transmission: sexual contact, blood, mother-to-child, shared needles
ELISA = screening test; Western Blot = confirmatory test
AIDS when CD4+ count drops below 200/μL → opportunistic infections
Cancer
- Oncogenes: Genes that cause cancer when activated (from proto-oncogenes)
- Tumour suppressor genes: Normally prevent cancer (e.g., p53, Rb); mutations → cancer
- Benign tumour: Non-spreading, confined. Malignant tumour: Invasive, metastasis (spread via blood/lymph)
- Carcinogens: UV rays, tobacco, asbestos, aflatoxins, certain viruses
- Detection: Biopsy, MRI, CT scan, blood tests for tumour markers
- Treatment: Surgery, radiation therapy, chemotherapy, immunotherapy
Drugs and Alcohol Abuse
| Category | Examples | Effects |
|---|---|---|
| Opioids | Morphine, Heroin, Smack | Sedative, depressant, highly addictive |
| Cannabinoids | Marijuana, Hashish, Ganja | Euphoria, affects cardiovascular system |
| Coca alkaloid | Cocaine | Stimulant, interferes with dopamine transport |
| Hallucinogens | LSD | Hallucinations, altered perception |
Quick Revision Points
- Malaria: Plasmodium, female Anopheles; Filariasis: Wuchereria, female Culex
- Innate immunity: born with; Acquired: after exposure (active/passive)
- Vaccination: active artificial immunity; Serum: passive artificial immunity
- HIV: retrovirus, attacks CD4+ T-cells; ELISA screening, Western Blot confirmation
- Cancer: oncogenes (promote), tumour suppressors (prevent); benign vs malignant
- Antibodies: IgG (most common), IgA (colostrum), IgE (allergy)
Chapter Navigation
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Related Chapters in Class 12 Biology
- Microbes in Human Welfare Class 12 Notes
- Biotechnology Principles and Processes Class 12 Notes
- Evolution Class 12 Notes
Practice What You Learned
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