Science · Class 12
Human Health and Disease
Learn Human Health and Disease with notes, examples, and practice questions.
5 sections15–25 min read8 MCQs · 3 examples
Chapter Overview
Immunity has two arms: innate (fast, non-specific) and acquired (specific, memory-bearing).
Health is a state of complete physical, mental, and social well-being. This chapter covers pathogens, immunity, AIDS, cancer, drugs, and common diseases — heavily tested in NEET.
Common Diseases
- Pathogens: bacteria, viruses, fungi, protozoans, helminths
- Typhoid: Salmonella typhi; Widal test
- Malaria: Plasmodium (protozoan); vector Anopheles mosquito
- Amoebiasis: Entamoeba histolytica
- Ringworm: fungal (not worm)
Immunity
- Innate: barriers (skin, mucus), phagocytes, inflammation, fever
- Acquired: B cells (humoral/antibodies) + T cells (cell-mediated)
- Active immunity: own antibodies (infection/vaccine)
- Passive immunity: ready-made antibodies (mother to baby, antiserum)
- Vaccination: memory B and T cells — preventive
HIV/AIDS
- HIV attacks helper T cells (CD4+) → immune collapse
- Transmission: blood, sexual contact, mother to child — not casual touch
- ELISA and Western blot for detection
- No cure; ART slows progression
Cancer & Drugs
- Oncogenes / tumour suppressors; metastasis
- Treatment: surgery, radiotherapy, chemotherapy, immunotherapy
- Drug abuse: opioids, cannabinoids, cocaine — addiction and rehabilitation
- Smoking: nicotine + tar → lung cancer, COPD
Solved Examples
Step-by-step solutions — read each step before checking the final answer.
Example 1: Active vs Passive
Vaccination is which type of immunity?
- 1Body produces own antibodies and memory cells after antigen exposure.
- 2Active acquired immunity.
Answer
Active acquired immunity
Example 2: Malaria
Name vector and pathogen of malaria.
- 1Pathogen: Plasmodium species
- 2Vector: female Anopheles mosquito
Answer
Plasmodium; Anopheles
Example 3: HIV Target
Which cells does HIV primarily destroy?
- 1Helper T lymphocytes (CD4+)
- 2Weakens cell-mediated and humoral immunity
Answer
Helper T cells (CD4+)
Key Points to Remember
- ✓ Interferons: protein antivirals from virus-infected cells
- ✓ Allergy: IgE-mediated hypersensitivity
- ✓ Autoimmunity: immune system attacks self (rheumatoid arthritis)
- ✓ Know life cycles: Plasmodium in liver and RBC
Exam Tips
- • Tabulate disease — pathogen — vector — symptoms
- • Draw antibody structure (Y-shaped, variable region)
- • Differentiate innate vs acquired with examples
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Formula Cheat Sheet
Quick reference — NCERT board exam formulas
Diseases — Pathogen & Vector
- Typhoid:Salmonella typhi (bacterium) ; Widal test
- Malaria:Plasmodium (protozoan) ; vector: female Anopheles
- Amoebiasis:Entamoeba histolytica (protozoan)
- Ringworm:Dermatophyte fungi (not a worm)
- AIDS:HIV destroys helper T cells (CD4+) ; detected by ELISA / Western blot
Immunity
- Innate immunity:Non-specific — skin, mucus, phagocytes, inflammation, fever
- Acquired immunity:Specific — B cells (antibodies) + T cells (cell-mediated)
- Active immunity:Body produces own antibodies (infection / vaccination)
- Passive immunity:Ready-made antibodies (mother → baby via IgA in colostrum)
- Vaccination:Antigen exposure → memory B & T cells → faster secondary response
- Antibodies (immunoglobulins): Y-shaped proteins produced by plasma B cells
Practice MCQs — Human Health and Disease
Test your understanding with topic-wise multiple choice questions. Explanations appear after each answer.
Question 1 of 8Score: 0/0
Malaria is caused by: