Human Health and Disease covers what health really means, the common bacterial, viral, protozoan, worm and fungal diseases of humans with their pathogens and modes of spread, and how the body defends itself through innate and acquired immunity. It also deals with AIDS, cancer, vaccination, allergies and drug and alcohol abuse. It is a high-yield, mostly fact-based chapter that reliably delivers easy NEET marks in the Human Physiology and Biology in Human Welfare units.
Class 12 Biology · Zoology – swipe through all 10 cards to understand the whole chapter.
Health and Disease
Health is total well-being, not just the absence of being sick.
Trap: ‘absence of disease only’ is always the WRONG NEET option.
- Disease = disturbance in normal body function (signs seen, symptoms felt)
- Infectious/communicable: caused by pathogens, spread person to person
- Non-infectious: confined to the person (cancer, allergy, diabetes)
Pathogens and Transmission
Knowing how a pathogen spreads tells you exactly how to stop it.
Each route has a signature prevention; match route → prevention.
- Air/droplets → common cold, pneumonia (masks, cover coughs)
- Food/water → typhoid, amoebiasis (clean water, hygiene)
- Vector → malaria (Anopheles); body fluids → AIDS
Bacterial and Viral Diseases
Match the pathogen to its disease, organ and test.
Common cold attacks the nose, NOT the lungs.
- Typhoid: Salmonella typhi, food/water, sustained high fever
- Pneumonia: Streptococcus pneumoniae, fills the alveoli
- Common cold: Rhinoviruses, upper respiratory tract
Protozoan, Worm and Fungal Diseases
These are heavily tested as match-the-pathogen pairs.
Ringworm is a FUNGUS, not a worm — a classic trap.
- Malaria: P. falciparum = malignant; haemozoin gives chill-and-fever
- Amoebiasis: Entamoeba histolytica, houseflies are carriers
- Ascariasis = Ascaris (roundworm); Filariasis = Wuchereria; Ringworm = fungi
Innate Immunity
A fast, non-specific defence present from birth — no memory.
Interferons belong to the cytokine barrier, protecting uninfected cells from viruses.
- Physical: skin and mucus lining
- Physiological: stomach acid, saliva, tears
- Cellular: PMNL-neutrophils, monocytes, macrophages, NK cells
Acquired Immunity and Antibodies
A specific defence with memory — the reason vaccines work.
Graft rejection = CMI (T-cells); antibody is H2L2, never H4L2.
- Humoral (AMI): B-cells secrete antibodies into blood/lymph
- Cell-mediated (CMI): T-cells; cause graft rejection
- Five classes ‘GAMED’: IgG, IgA, IgM, IgE, IgD
Primary vs Secondary Response
The second meeting with an antigen is faster and far stronger.
This anamnestic response is the basis of a booster vaccine dose.
- Primary response is slow, weak, leaves memory cells behind
- Secondary (anamnestic) starts earlier and rises much higher
- Memory cells fire instantly on re-exposure to the same antigen
AIDS and Cancer
AIDS is immune collapse; cancer is runaway cell division.
AIDS is NOT spread by hugging, food or mosquitoes; metastasis marks malignant tumours.
- HIV enters macrophages first, then destroys helper T-cells
- Cancer cells lose contact inhibition; malignant ones metastasise
- Carcinogens: physical (UV, X-ray), chemical (tobacco), biological (oncogenic viruses)
Active vs Passive Immunity and Allergy
You either build your own antibodies or receive ready-made ones.
Colostrum (IgA), ATS and antivenom are passive; vaccination is active.
- Allergy: allergen → IgE on mast cells → release histamine, serotonin
- Treat allergy with anti-histamines; mediator is IgE
- Autoimmunity attacks own cells, e.g. rheumatoid arthritis
Drugs and Alcohol Abuse
The highest-yield facts are the drug → source → effect links.
LSD is from the fungus Claviceps purpurea, NOT a plant — a guaranteed trap.
- Cannabinoids: Cannabis sativa inflorescence, affect cardiovascular system
- Cocaine blocks dopamine transport; opioids bind CNS opioid receptors
- Nicotine stimulates adrenal gland → adrenaline/nor-adrenaline → raises BP
📝 Practice Human Health and Disease — 10 NEET PYQs
Real previous-year questions · with answers & solutions
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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
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Frequently Asked Questions
Health is a state of complete physical, mental and social well-being, not merely the absence of disease or infirmity. Treating health as only the absence of disease is the classic wrong NEET option.
Innate immunity is non-specific, present from birth and has no memory, acting through physical, physiological, cellular and cytokine barriers. Acquired immunity is pathogen-specific, develops after exposure and has memory, which is why a secondary response is faster and stronger and why vaccines work.
In active immunity the body makes its own antibodies after exposure to an antigen or vaccine, so it is slow to develop but provides memory and long-lasting protection. In passive immunity ready-made antibodies are given directly, as in colostrum, anti-tetanus serum or antivenom, giving fast but short-lived protection with no memory.
High-yield match-the-pair facts include typhoid by Salmonella typhi (Widal test), pneumonia by Streptococcus pneumoniae, common cold by rhinoviruses, malaria by Plasmodium spread by female Anopheles, amoebiasis by Entamoeba histolytica, ascariasis by Ascaris and filariasis by Wuchereria. Remember ringworm is caused by fungi, not a worm.
Yes, it is a high-weightage and scoring chapter, with questions on immunity, disease pathogens, AIDS, cancer and drug abuse appearing almost every year. HIV is a retrovirus that uses reverse transcriptase to make DNA from its RNA, and AIDS is confirmed by the ELISA test.