Revision Notes: Class 8 Science Chapter 3 Health The Ultimate Treasure

Class 8 Science Chapter 3: Health: The Ultimate Treasure — Quick Revision Notes

• Health (WHO definition): a state of complete physical, mental and social well-being — not merely the absence of disease.
• Communicable diseases: caused by pathogens (bacteria, viruses, fungi, protozoa) and transmissible between people — e.g. flu, typhoid, chickenpox, cholera.
• Non-communicable diseases: not transmissible; linked to lifestyle, genetics or environment — e.g. diabetes, asthma, heart disease.
• Spread routes: air/droplets (flu, measles, TB), contaminated water/food/faecal-oral route (cholera, typhoid, Hepatitis A, polio), vectors like mosquitoes (malaria, dengue).
• Immunity: the body’s natural ability to resist pathogens, involving white blood cells and antibodies.
• Primary vs secondary immune response: first exposure to a pathogen triggers a slow, weak response; memory B/T cells formed during this allow a much faster, stronger response on re-exposure.
• Vaccination: trains the immune system in advance (using a weakened/dead/partial pathogen) to build memory cells, enabling a rapid response if the real pathogen is encountered.
• Antibiotics: work only against bacteria, not viruses; misuse for viral infections is ineffective and promotes antibiotic resistance.
• Prevention: combines individual habits (hygiene, diet, exercise, avoiding tobacco/alcohol, sleep) with community measures (vaccination drives, sanitation campaigns, vector control).
• Mental health link: stress and social isolation weaken immunity and contribute to non-communicable disease risk, reflecting the WHO’s broader definition of health.

Written by Satish

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