MG SCHOOL SCIENCE CLASS 8

HEALTH: THE ULTIMATE TREASURE

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1. Meaning of Health 2. Student's Story 3. Ayurveda 4. Staying Healthy 5. Good & Bad Habits 6. Healthy Lifestyle 7. Clean Environment 8. Feelings & Relationships 9. Signs & Symptoms 10. Types of Diseases 11. Spread of Diseases 12. Prevention 13. Non-Communicable Diseases 14. Disease Control 15. Immunity & Vaccines 16. Antibiotics 17. Managing Diseases 18. Key Points

01 Health: Is It More Than Not Falling Sick?

Meaning of Health

Health is not just about not being sick. It means feeling good in your body, mind and social life.

WHO Definition: According to the World Health Organization, health is a state of complete physical, mental and social well-being, not just the absence of disease.

A Healthy Person Can

Do tasks efficiently.
Handle difficult situations well.
Get along with friends and other members of society.

Key Aspects of Health

Physical Health: Taking care of the body through proper food, exercise and sleep.
Mental Health: Staying positive and managing stress and difficult feelings.
Social Health: Having good relationships with friends, family and other people.

02 A Student's Story

A Class 8 boy moved to a new city and school. He felt lonely because he had no friends and his parents were busy. He spent more time on his phone and social media.

Problems Faced

Headaches.
Weight loss.
Trouble sleeping.

Cause and Solution

A doctor suggested reducing screen time and meeting a counsellor. The counsellor helped the boy make friends, and his health improved.

Important Learning:

Loneliness and excessive screen time caused both physical and mental health problems.
Making new friends and receiving support from adults helped him feel better.

03 Ayurveda and Health

Ayurveda teaches that health is related to a balance among the body, mind and surroundings.
Dinacharya: Daily routine.
Ritucharya: Seasonal routine.
Diet: Eating fresh and wholesome foods suited to one's prakriti, or body type.
Mind and Body Practice: Regular exercise, cleanliness, restful sleep and a calm mind through yoga, meditation and mindfulness.

Ayurveda gives importance to balance in the body, mind and surroundings.

04 How Can We Stay Healthy?

Healthy Practices

Eating nutritious food.
Keeping clean, including maintaining personal hygiene and clean surroundings.
Exercising regularly.
Getting enough sleep.
Spending time with family and friends.
Having a positive attitude.

05 Good and Bad Habits

Good Habits

Keep yourself clean and maintain personal hygiene.
Eat a healthy and balanced diet.
Exercise regularly.
Make time to relax or meditate every day.

Bad Habits

Spending too much time on mobile phones or screens.
Eating fast food or junk food every day.
Sleeping very late or not getting enough sleep.
Skipping meals, especially breakfast.

Remember: Healthy habits support physical and mental well-being.

06 Maintaining a Healthy Lifestyle

Our health depends on many factors. These include our lifestyle, which means the way we live, and our environment, which means our surroundings.

Important Factors

Balanced Diet: Eat a balanced diet containing plenty of fruits, vegetables and whole grains. Limit junk food and foods and drinks high in fat or added sugar.
Physical Activity: Stay physically active. Play outdoors, walk, run, cycle or exercise.
Screen Time: Limit screen time and spend more time in nature.
Sleep: Get enough sleep to help the body and mind rest.
Mindfulness: Practise yoga or pranayama, which consists of simple breathing exercises, regularly.
Say NO to Harmful Substances: Avoid tobacco, alcohol and addictive drugs.

07 Keeping the Environment Clean

Playground Safety: A clean and well-maintained playground is safer and healthier for playing. A dirty and polluted playground may contain flies and mosquitoes and can make us sick.
Clean Air and Water: Clean air and water are important for good health. Pollution from vehicles or factories can cause coughing and breathing problems such as asthma.
Air Quality Index (AQI): The AQI shows how clean or polluted the air is.
Surroundings Hygiene: Avoid littering and keep your area tidy. A clean environment reduces the risk of diseases and helps us stay healthy and feel good.

08 Importance of Feelings and Relationships

Mental and Emotional Aspect: Health is not just about the body; feelings and relationships matter too.
Impact of Loneliness: Even with good food and clean surroundings, a person may feel unhappy if they are lonely or upset.
Social Connection: Spending time with friends and family, talking, laughing and having fun helps keep the mind healthy.

Good relationships and emotional well-being are important parts of good health.

09 How Do We Know That We Are Unwell?

Our body usually works in a specific way to keep us healthy. When we feel unwell, something inside our body may not be working properly. We experience symptoms and signs that show that we are not healthy.

Symptoms vs Signs

Symptoms	Signs
What we feel when we are unwell.	Changes that can be seen or measured by another person, such as a doctor.
Pain, tiredness and dizziness.	Fever, rash, high blood pressure and swelling.

Remember: Symptoms are felt by the person, whereas signs can be observed or measured by others.

10 Diseases: What Are the Causes and Types?

Meaning of Disease

A disease is a condition that stops the body or mind from working normally. It happens when one or more organs or organ systems do not function properly.

Causes of Diseases

Pathogens: Germs such as bacteria, viruses, fungi, worms or protozoa (single-celled organisms) can cause diseases.
Poor Nutrition: Not eating enough healthy food can lead to deficiency diseases.
Unhealthy Lifestyle: Habits such as lack of exercise or an unhealthy diet contribute to diseases.

Two Major Types of Diseases

Communicable Diseases	Non-Communicable Diseases
Diseases that can spread from one person to another.	Diseases that cannot spread from person to person.
Caused by pathogens.	Linked to lifestyle, diet, environment or organ function.
Typhoid, dengue, flu, chickenpox and COVID-19.	Diabetes, cancer, heart disease and asthma.

11 How Are Communicable Diseases Caused and Spread?

All communicable diseases are caused by pathogens that enter our body through various routes.

Modes of Transmission

Air: Pathogens in tiny droplets are released by coughing, sneezing or talking and breathed in by others. Examples: Flu and tuberculosis.
Direct Contact: Touching an infected person, for example, while shaking hands.
Indirect Contact: Sharing items such as towels or handkerchiefs.
Contaminated Food or Water: Consuming unsafe food or water contaminated with bacteria, viruses or parasites. Examples: Cholera and typhoid.
Vectors: Insects such as mosquitoes transmit malaria and dengue. Houseflies carry pathogens to food.

12 Prevention of Communicable Diseases

Preventive Measures

Keep yourself and your surroundings clean.
Practise good hygiene, such as washing your hands with soap.
Cover your mouth and nose when coughing or sneezing.
Wear a mask in crowded places when required.
Avoid sharing personal items such as towels and handkerchiefs.
Keep food and water clean.
Stay at home and rest when unwell to recover and prevent spreading disease.
Use mosquito nets and repellents and control insect breeding.

Good hygiene, sanitation and cleanliness help prevent the spread of communicable diseases.

13 How Are Non-Communicable Diseases Caused?

Non-communicable diseases (NCDs) are not caused by infections or germs. Instead, they are linked to:

Lifestyle Factors: Unhealthy habits such as eating too much junk food, lack of exercise, smoking or excessive stress lead to diabetes, heart disease or cancers.
Nutritional Deficiencies: Lack of essential nutrients causes deficiency diseases.
Environmental Factors: Pollution and harmful chemicals contribute to asthma and cancers.
Hormonal Imbalances: Imbalances of hormones in the body, for example, diabetes.
Chronic Nature: NCDs usually last for a long time (often more than 3 months) and require ongoing care.

Examples of Deficiency Diseases

Nutrient Deficiency	Disease
Vitamin C	Scurvy
Iron	Anaemia
Iodine	Goitre

14 How to Prevent and Control Diseases?

Golden Rule: Prevention is better than cure.

This means it is easier and wiser to prevent a disease than to try to cure it after becoming sick. Good sanitation and cleanliness are simple and effective ways to reduce disease spread.

Case Study – Odisha: Community-Led Sanitation Campaign

Location and Action: In Bhadrak district, Odisha, a community campaign encouraged people to build and use toilets.
Impact: As families stopped open defecation, child health improved and diseases such as diarrhoea and infections were greatly reduced.
Takeaway: Building toilets, keeping surroundings clean and disposing of waste properly prevent germs from spreading. Community action has a major impact on public health.

15 Ability of the Body to Fight Diseases (Immunity and Vaccines)

What Is Immunity?

The ability of the body to fight diseases is called immunity. Our immune system is a group of special cells, tissues and organs that recognise and fight harmful germs.

Role of Vaccines

Acquired Immunity: Vaccines are injections or drops that teach the immune system to recognise and destroy specific germs before they make us sick.
How They Work: Vaccines use harmless parts, dead or weakened forms of a germ. Example: Tetanus shot contains an inactivated bacterial toxin.
Common Vaccines: Vaccines against polio, measles, hepatitis and other diseases are given during childhood.

Edward Jenner and the Smallpox Vaccine

Discovery: In the late 1700s, Edward Jenner observed that people who had cowpox did not get smallpox.
He prepared the first vaccine using material from cowpox sores, leading to global eradication of smallpox.
Variolation in India: Earlier in India, variolation involved using a small amount of material from a mild smallpox infection to protect healthy people.

Importance of Vaccines and India's Role

Disease Prevention: Vaccines prevent serious illnesses before a person becomes sick.
Community Protection: High vaccination rates create herd protection, guarding those who cannot be vaccinated.
Safety: Vaccines are thoroughly tested for safety.
India's Global Role: India is a major global vaccine producer, supplying vaccines worldwide and playing a key role during the COVID-19 pandemic.

16 Treatment of Diseases and Antibiotics

If our immune system cannot fight off an infection, doctors prescribe medicines, including antibiotics when required.

What Are Antibiotics?

Definition: Medicines used to kill bacteria or stop them from multiplying.
Examples: Used for treating bacterial infections such as tuberculosis and typhoid.
Crucial Limitation: Antibiotics DO NOT work against viral infections such as colds, flu or COVID-19.

Discovery of Antibiotics

Alexander Fleming (1928): Discovered penicillin in London after observing that mould on a Petri dish killed harmful bacteria around it.

Antibiotic Resistance

Definition: Occurs when bacteria change and stop being killed by antibiotics, making infections much harder to treat.
Causes: Taking antibiotics for viral infections, not finishing prescribed doses and overuse of antibiotics in farm animals and crops.

Important: Antibiotics should be used only when prescribed by a qualified doctor.

17 Managing Non-Communicable Diseases

Diseases such as diabetes, cancer and heart disease are managed through:

Taking prescribed medicines as advised by doctors.
Healthy lifestyle changes in diet and exercise.
Rehabilitation (special help to recover or function better).
Early diagnosis and regular health check-ups.

18 Key Points to Remember

⭐ Chapter Revision – Important Points

Health Definition: Health means complete physical, mental and social well-being, not just freedom from diseases.
Happiness and Health: Being happy helps us stay active and healthy; good health improves mood.
Disease: A condition that stops the body or mind from working normally.
Symptoms vs Signs: Symptoms are felt by the person (pain, tiredness); signs are visible or measurable (fever, rash).
Communicable Diseases: Caused by pathogens and spread between people or via air, water, food, contact or vectors.
Non-Communicable Diseases: Not caused by germs; linked to lifestyle, diet, environment or hormonal imbalances.
Hygiene and Sanitation: Good personal hygiene and clean surroundings are essential to prevent disease spread.
Immunity and Vaccines: The immune system fights germs; vaccines train it safely to provide acquired immunity.
Antibiotics: Treat bacterial infections only; misuse causes dangerous antibiotic resistance.
Golden Rule: Prevention is better than cure. Healthy habits, vaccination, cleanliness and staying informed protect our health.

About Me

Friday, 6 November 2026

Class 8 Science