📋 Table of Contents — Click to Jump
Section 1
What is Health? — Section 3.1
WHO Definition: Health is a state of complete physical, mental, and social well-being — and NOT merely the absence of disease!
Being healthy is much more than just not being sick! It includes feeling good physically, staying mentally positive, and maintaining strong relationships.
@edugrown- Mental Health: Positive thinking, stress management, emotional balance
- Physical Health: Body functioning properly, staying physically active
- Social Health: Good relationships, time with friends and family
- A healthy person can perform tasks efficiently and cope well in difficult situations
Ayurveda's view: True health means balance of body, mind and surroundings. Following Dinacharya (daily routine) and Ritucharya (seasonal routine), eating wholesome food, yoga, meditation and restful sleep — this is genuine health!
@edugrownReal Example: A student moved to a new school, felt lonely, spent more time on his phone → headaches, weight loss, poor sleep. A counsellor helped him make friends → health improved. Loneliness is a health problem too!
Section 2
How to Stay Healthy? — Section 3.2
Our health depends on two things: Lifestyle (how we live) and Environment (our surroundings).
@edugrown🥗 Balanced Diet
@edugrown🏃 Exercise Daily
@edugrown🚫 No Smoking
@edugrown🧘 Manage Stress
@edugrown😴 Enough Sleep
✅ Healthy Habits
- Eat fruits, vegetables and whole grains
- Walk, run, cycle or exercise daily
- Get adequate sleep — let your body recover
- Practice yoga and pranayama regularly
- Spend time in nature; limit screen time
- Maintain social connections with family and friends
❌ Unhealthy Habits
- Excessive time on mobile and digital screens
- Eating fast food and junk food every day
- Sleeping very late or not enough
- Skipping meals, especially breakfast
- Tobacco, alcohol and addictive drugs
- Social isolation and loneliness
Section 3
Keep the Environment Clean — Section 3.2.2
@edugrown✅ Clean playground — healthy environment
@edugrown❌ Dirty playground — flies, mosquitos, disease risk!
- Clean air is essential: Air pollution from vehicles and factories causes coughing and asthma
- AQI (Air Quality Index): Measures how clean the air is — lower = better for health
- Clean water: Contaminated water leads to water-borne diseases
- Keeping surroundings clean prevents flies and mosquito breeding
- Mental health matters too: Feeling lonely also affects health — spend time with loved ones!
Section 4
How Do We Know We Are Unwell? — Section 3.3
Symptom: What we feel — pain, tiredness, dizziness. This is reported by the patient and cannot be directly seen or measured by a doctor.
Sign: What can be seen or measured — fever, rash, high blood pressure, swelling. These are directly observed by the doctor.
- Symptoms: Pain, fatigue, dizziness
- Signs: Fever, rash, high blood pressure, swelling
- Both together help doctors diagnose what is causing the illness
- Disease occurs when one or more organs or organ systems stop functioning properly
Section 5
Diseases — Causes and Types — Section 3.4
Pathogen: Disease-causing organisms — bacteria, viruses, fungi, worms, protozoa. These are the enemy organisms that enter our body and cause disease.
@edugrown🔄 How diseases spread — NCERT Fig 3.4
🦠 Communicable Diseases
Caused by pathogens. Can spread from one person to another.
Examples: Typhoid, Dengue, Flu, Chickenpox, COVID-19
💼 Non-Communicable Diseases
Not caused by pathogens — linked to lifestyle, diet and environment. Do not spread.
Examples: Cancer, Diabetes, Asthma, Obesity
- By Air: Coughing, sneezing (Flu, TB, Chickenpox)
- Direct Contact: Shaking hands with an infected person
- Indirect Contact: Sharing clothes, utensils or personal items
- Food/Water: Contaminated food or water (Cholera, Typhoid)
- Vectors: Mosquitoes and houseflies carry pathogens (Malaria, Dengue)
- Parasites: Worms living inside the body, feeding on nutrients (Ascariasis)
📊 India Alert: Non-communicable diseases (diabetes, heart disease, cancer) are increasingly common — due to processed food, less exercise and longer lifespans. Today, NCDs are the leading cause of death in India!
Section 6
Communicable Diseases — NCERT Table 3.1
@edugrown🤧 Common Cold
@edugrown🔴 Chickenpox
@edugrown🤒 Measles
@edugrown😷 Tuberculosis
| Disease | Causal Agent | Symptoms | Prevention |
|---|---|---|---|
| 💨 Spread Through Air | |||
| Common Cold / Flu | Virus | Nasal congestion, sore throat, fever, cough | Wash hands regularly, wear mask, avoid sharing items |
| Chickenpox | Virus | Mild fever, itchy rashes, blisters | Patient isolation, mask, Vaccination |
| Measles | Virus | Fever, reddish rashes on neck and ears | Isolation, good hygiene, Vaccination |
| Tuberculosis (TB) | Bacteria | Cough, fever, fatigue, night sweats | Avoid close contact with TB patients, mask, Vaccination |
| 🍽️ Spread Through Contaminated Water/Food | |||
| Hepatitis A | Virus | Fatigue, jaundice, nausea, vomiting | Boil drinking water, Vaccination |
| Cholera | Bacteria | Severe diarrhoea, dehydration | Personal hygiene, boiled water, cooked food, Vaccination |
| Typhoid | Bacteria | Headache, abdominal pain, fever, diarrhoea | Hygiene, boiled water, properly cooked food, Vaccination |
| Ascariasis | Worms | Worms in stool, weight loss, anaemia | Good hygiene, properly cooked food, clean water |
| 🦟 Transmitted by Insects (Vectors) | |||
| Malaria | Protozoa | High fever, profuse sweating, periodic chills | Mosquito nets, repellents, no stagnant water near home |
| Dengue Fever | Virus | Fever, headache, muscle and joint pain | Mosquito nets, repellents, long-sleeved clothing |
@edugrown🫁 Hepatitis A
@edugrown🤢 Cholera
@edugrown🤕 Typhoid
@edugrown🪱 Ascariasis (roundworms)
@edugrown🦟 Malaria — transmitted by mosquitoes
General Precautions: Wash hands with soap ✅ · Cover mouth and nose ✅ · Wear mask in crowded places ✅ · Do not share personal items ✅ · Keep home, food and water clean ✅ · Stay home and rest when unwell ✅
Section 7
Non-Communicable Diseases — Section 3.4.2
- NCDs: Not caused by pathogens — linked to lifestyle, diet and environment
- Chronic Diseases: Last more than 3 months — Cancer, Diabetes, Asthma
- Deficiency Diseases: Caused by lack of specific nutrients — Scurvy, Anaemia, Goitre
- NCDs are currently the leading cause of death in India — a serious public health concern
Diabetes — India Alert: India has over 100 million people with diabetes (ICMR report)! Caused by hormonal imbalances, unhealthy diet, lack of exercise and obesity.
| NCD | Signs / Symptoms | Suggested Lifestyle Changes |
|---|---|---|
| Obesity | Excessive weight gain | Balanced diet and regular exercise |
| Diabetes | Frequent urination, excessive thirst, weight loss, tiredness, slow wound healing | Healthy diet, regular exercise, reduce sugar intake |
| High Blood Pressure | Headache, dizziness (often without symptoms) | Reduce salt intake, exercise, manage stress |
| Heart Disease | Chest pain, breathlessness | Less oily food, exercise, no smoking |
@edugrown🔬 Kamal Ranadive (1917–2001)
A pioneering biomedical researcher who studied the link between hormones, viruses and cancer. Her work demonstrated how tobacco, diet and pollution raise cancer risk. She strongly highlighted the importance of a healthy lifestyle in cancer prevention.Section 8
Prevention and Immunity — Section 3.5
Immunity: The body's natural ability to fight diseases. Our body has a specialised Immune System that identifies and destroys harmful pathogens.
- Wash hands with soap regularly — reduces infection risk by 50%!
- Wear a mask in crowded areas
- Stay home and rest when unwell — avoid spreading the disease to others
- Eat clean, properly cooked food
- Use safe drinking water at all times
- Use proper sanitation facilities — avoid open defecation
Odisha Case Study: A community sanitation campaign in Bhadrak district reduced open defecation → child health improved, diarrhoea and infection cases fell significantly! Simple sanitation = major health impact.
Section 9
How Do Vaccines Work?
Vaccine: Trains the immune system to recognise and attack harmful germs — without you actually getting the disease. This creates Acquired Immunity — protection developed after exposure to a pathogen or a vaccine.
@edugrown💉 Childhood vaccines protect against Polio, Measles, Tetanus and Hepatitis
- Vaccines are preventive, not curative — they prevent disease before it occurs
- Vaccines can be made from: weakened/dead pathogens, inactive parts, or harmless germ parts
- Getting vaccinated protects not just you, but everyone around you!
- India = World's largest vaccine producer! Supplied over 200 crore doses globally during COVID-19!
@edugrownEdward Jenner — First Vaccine (1700s): Jenner noticed milkmaids who got cowpox never caught smallpox. He injected cowpox sap into a boy — who then showed immunity to smallpox! This was the world's very first vaccine.
@edugrown📊 1965 vaccine campaign → 1979: Smallpox completely eradicated from the world!
India's Scientific Heritage: Long before modern vaccines, India practised Variolation — using material from a smallpox sore to scratch the skin, creating mild infection and building immunity. Practitioners of this method were called Teekedaars!
Section 10
Antibiotics and Antibiotic Resistance — Section 3.5.1
Antibiotic: A medicine that kills bacteria. Works only against bacterial infections — NOT effective against viruses or protozoa! Example: Penicillin.
@edugrownDiscovery of Penicillin (1928): Alexander Fleming in London noticed that a mould growing on a discarded petri dish had stopped bacteria from growing. He realised the mould released a bacteria-killing substance — Penicillin, the world's first antibiotic! A famous chance discovery.
Antibiotic Resistance — A Major Threat! Overuse or incorrect use of antibiotics causes bacteria to become resistant — they survive and multiply despite antibiotic treatment. This makes common infections much harder or impossible to treat.
@edugrown🔄 How antibiotic resistance spreads in the community — NCERT Fig 3.5(a)
@edugrown📖 How bacteria develop resistance and how to prevent it — NCERT Fig 3.5(b)
- Only take antibiotics prescribed by a doctor — never self-medicate
- Always complete the full course — do not stop midway even if you feel better
- Avoid giving antibiotics to animals unnecessarily
- Traditional medicine (Ayurveda, Siddha, Unani) supports daily well-being but may not be effective for all diseases
⭐ Key Takeaways — Chapter 3 Summary
- Health = Physical + Mental + Social well-being — not just the absence of disease!
- WHO: "A state of complete physical, mental and social well-being"
- Stay healthy with: balanced diet, exercise, adequate sleep, yoga, no smoking or alcohol
- A clean environment — fresh air, safe water and clean surroundings — is essential for good health
- Symptom = what we feel; Sign = what can be seen or measured
- Communicable diseases are caused by pathogens and can spread; NCDs are linked to lifestyle
- Vectors = insects that carry pathogens (mosquitoes → malaria, dengue)
- Immunity = the body's natural defence; the immune system fights pathogens
- Vaccines train the immune system — creating acquired immunity
- Antibiotics only work against bacteria — not viruses!
- Antibiotic resistance develops due to misuse — take antibiotics wisely!
- NCDs require: medication + lifestyle changes + early diagnosis
🎓 "Prevention is better than cure!" — Stay Healthy! 💚
✏️ Notes by @edugrown · Chapter 3 · Curiosity – NCERT Class 8 Science · Reprint 2026-27