Students can rely on these Class 8 Science Notes Chapter 3 Health The Ultimate Treasure Class 8 Notes for complete exam preparation.
Class 8 Science Chapter 3 Health The Ultimate Treasure Notes
Class 8 Science Curiosity Chapter 3 Notes
Class 8 Science Chapter 3 Notes – Health The Ultimate Treasure Notes Class 8
→ Health A state of complete physical, mental, and social well-being, not merely the absence of disease.
→ Pathogens Microorganisms such as bacteria, viruses, protozoan, and fungi that cause diseases.
→ Acute disease A disease that lasts for a short duration and usually results in complete recovery.
→ Chronic disease A long-lasting disease that may persist for life and causes long-term effects on health.
→ Communicable disease An infectious disease that spreads from one person to another through air, water, contact, or vectors.
→ Non-communicable Disease (NCD) A disease that does not spread from person to person and is often caused by lifestyle or genetic factors.
→ Immunity The body’s natural defence system that protects against disease-causing organisms.
→ Vaccination A process of developing immunity by introducing weakened or dead pathogens to stimulate the immune response.
→ Antibiotics Medicines that kill or inhibit the growth of bacteria without harming human cells.
→ Antibiotic resistance A condition where bacteria develop the ability to survive treatment with antibiotics that once killed them.
→ Which international organisation has defined health as a state of complete physical, mental, and social well-being, rather than just the absence of disease?
→ What is the name of the ancient Indian system of medicine that focuses on balancing body constitution through practices like dinacharya and ritucharya?
→ What index is used to measure the level of air pollution and indicates whether the air quality is clean or polluted?
→ Why social harmony is needed for a person to achieve good individual health?
→ What does helps a physician to confirm a disease?
→ When compared to an acute disease patient, a chronic disease patient recovers after a long time. Is it true? Give one reason.
→ Name the diseases that spread to healthy people after coming in contact with a sick person.
→ Name the type of disease that remain restricted only to a particular person.
→ Which type of immunity is inbuilt in our body from the time of birth and serves as the first line of defence against infections?
→ Which virus was used in Edward Jenner’s early experiments to create a protective response against the deadly smallpox virus?
→ Which common health condition in children, often caused by rotavirus, is prevented through the use of the vaccine developed under Dr. Bhan’s guidance?
→ What was the name of the traditional immunisation practice used in ancient India that involved the use of material from smallpox sores to induce immunity?
→ Name the term is used for the medicines specifically designed to kill or stop the growth of bacteria.
→ Which scientist is credited with the discovery of the first antibiotic, penicillin, in 1928?
→ A doctor refuses to give antibiotics for a flu patient. Based on your understanding, is the doctor’s decision medically justified? Yes/NO
→ Despite taking antibiotics, a patient’s infection worsens, and lab results show mutated bacteria. What might these bacteria have developed?
→ What basic hygiene practice is strongly recommended to reduce infections and limit the spread of antibiotic resistance?
Health
It is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity as defined by the WHO (World Health Organisation). Thus, being healthy means that one should feel good physically, mentally and socially.
Similarly, Ayurveda , India’s ancient system of medicine, emphasises that health is the result of harmony between the body, mind, and environment. It teaches that maintaining one’s prakriti (individual body constitution) through proper dinacharya (daily routine) and ritucharya (seasonal routine) is key to staying healthy.
Significance of Health
Good health has following advantages
- It increases our working efficiency. It helps us to perform various activities at our best.
- It helps us to cope up with the social and mental pressures without much difficulty.
- It contributes to overall well-being, making life more joyful and fulfilling.
Maintaining a Healthy Lifestyle
Maintaining a healthy lifestyle is essential for personal well-being. Good personal habits not only prevent diseases but also help in improving the quality of life. A healthy lifestyle includes
- Eating a balanced diet with limited oil and sugar.
- Doing regular exercise to keep the body fit.
- Practicing personal hygiene to prevent infections.
- Getting adequate sleep to keep the mind and body rested.
- Practicing yoga or simple breathing exercise like pranayama regularly.
- Saying ‘No’ to harmful substances like tobacco, alcohol and additive drugs.
Personal and Community Health
The health of every individual depends on the personal habits, economic status and physical environment. Personal health refers to the overall well-being of an individual.
But human beings live in communities therefore, the health of the community is also an important factor for an individual’s health.
Community health refers to the maintenance, protection and improvement (overall well-being) of the whole community in which an individual lives.
The following factors explain the relation between community and individual health.
- Social Environment : Our physical environment is decided by our surrounding. The place where we live (i.e. villages, towns or cities) is an important factor in our individual health.
- Public Cleanliness : The possibility of poor health increases if no agency ensures that garbage is collected and disposed. Open drain as well as stagnant water around us can lead to health . problems. Therefore, public cleanliness is important for individual health.
- Air quality and pollution : The quality of air we breathe affects our health. Air pollution from vehicles and factories can cause breathing problems like asthma and coughing. The Air Quality Index (AQI) shows how clean or polluted the air is.
- Social equality and harmony : A peaceful society where people treat each other kindly helps reduce stress and keeps people mentally and socially healthy.
Disease
Disease refers to any condition that disturbs or modifies the normal functioning of the body/living organisms. Each organ system of our body has specific organs to perform particular functions.
In the presence of a disease, functioning or the appearance of one or more systems of the body may change. These changes give rise to symptoms and signs of disease.
Symptoms and Signs of Diseases
Symptoms of diseases are the indications of something being wrong or unusual, such as cold, headache, cough, loose motions, etc. These indicate that there may be a disease but, they do not exactly indicate what the disease is. For example, a headache may rarely mean any fatal disease, it can simply means just official stress or any other disease.
Signs of a disease give more definite indications of the presence of a particular disease. They help the doctors (physicians) to diagnose the disease. For example, having high body temperature when one have fever.
Causes of Disease
- Diseases are mainly caused by harmful microorganisms called pathogens. These tiny organisms enter the body, multiply, and interfere with normal body functions.
- The main types of disease -causing pathogens are bacteria, viruses, worm, protozoan (single celled organism) and fungi. These pathogens spread in different ways, such as through air, water, food, or direct contact.
- Other disease may result from poor nutrition or an unhealthy lifestyle.
Types of Diseases
On the basis of duration of infection, diseases may be of following two types
(i) Acute diseases are the diseases that last only for very short period of time. Thus, they do not cause long-term harmful effects on human health. In these diseases, patients recover completely after the cure, e.g. common cold, cough, etc.
(ii) Chronic diseases are the diseases, which last for a long time, even as much as a lifetime. They cause drastic long-term effects on human health and need a regular treatment, e.g. cancer, Tuberculosis (TB), etc.
On the basis of causes and mode of transmission diseases can be broadly classified as
(i) Communicable disease
(ii) Non-Communicable disease
Communicable Disease
- Diseases caused by pathogen are called communicable diseases (also known as infectious disease). These diseases can spread from one person to another.
- These pathogens may enter the body through the air we breathe, by eating contaminated food, drinking unsafe water, or through direct contact with an infected person.
- Some communicable diseases also spread through insects like mosquitoes and houseflies, which carry and transfer disease causing germs. These insects are called vectors because they help spread the disease.
- In addition, some infectious diseases are caused by worms that live inside our bodies, especially in the digestive system. These worms feed on the nutrients from the host and live as parasites (organisms that live in or on another living being). Such worms usually spread through contaminated food, water, soil, or through contact with infected people or animals.
- Some examples of communicable diseases are typhoid, dengue, flu, chicken pox and COVID 19.
The following table shows examples of common communicable diseases, along with their causal agents, modes of transmission, symptoms, and preventive measures
Preventions of Communicable Diseases
Communicable diseases can be prevented by following simple and regular habits that help to stop the spread of harmful germs and are keeping everyone healthy.
- Maintaining personal and environmental cleanliness by keeping the body, clothes, home, and surroundings clean to reduce the chances of infection.
- Practicing good hygiene daily, such as bathing regularly, trimming nails, and wearing clean clothes.
- Washing hands thoroughly with soap and water, especially before eating, after using the toilet, and after returning home from outside, to remove disease- causing germs.
- Covering the mouth and nose while coughing or sneezing to prevent the spread of germs through air droplets.
- Wearing a mask in crowded or closed places, especially if someone nearby is unwell, to avoid breathing in harmful microbes.
- Avoiding sharing personal items like towels, handkerchiefs, or water bottles, as these are carrying infections.
- Ensuring that food and drinking water are clean and safe by storing them properly and avoiding food from unhygienic sources.
- Staying at home and taking rest when feeling unwell to help the body recover and to prevent spreading the infection to others.
Community-Led Sanitation Success in Odisha
In Bhadrak district of.Qdisha, a community-led sanitation campaign encouraged people to build and use toilets. This significantly reduced open defecation and led to better child health, with fewer cases of diarrhoea and other infections.
Non communicable disease (NCD)
- These are long-term diseases that do not spread from person to person. They often develop due to unhealthy lifestyles, poor diet, lack of exercise, or genetic factors.
- A type of NCD is deficiency diseases, occur when the body lacks essential nutrients such as vitamins and minerals. Common examples of these diseases are scurvy, anaemia and goitre, which are caused by lack of specific nutrients in the diet.
- Unlike communicable diseases, NCDs cannot be cured with simple medicines but can be managed through regular care and healthy habits.
- Therapies for NCDs focus on managing symptoms and improving quality of life through medication, lifestyle changes, and rehabilitation. Early diagnosis and continuous care are key to controlling disease progression and preventing complications.
Some non-communicable diseases are discussed in the table below.
| Diseases | Signs and symptoms | Suggested lifestyle changes |
| Diabetes | Frequent urination, excessive thirst, tiredness, slow healing of wounds | Reduce sugar intake, regular exercise, healthy diet, maintain healthy weight |
| Obesity | Excess body weight, breathlessness, fatigue, joint pain | Balanced diet, daily physical activity, limit junk food |
| Heart disease | Chest pain, shortness of breath, fatigue, irregular heartbeat | Low-fat diet, regular exercise, stress management, avoid tobacco and alcohol |
| Cancer | Unexplained weight loss, persistent pain, fatigue, lumps in body | Avoid tobacco, balanced diet, regular health check-ups, physical activity |
| Hypertension (high blood pressure) | Headaches, dizziness, blurred vision, chest discomfort | Low-salt diet, regular exercise, stress reduction, avoid processed foods |
- In recent times, non-communicable diseases like diabetes, heart disease, and cancer have become more common in India. These are referred to as chronic diseases.
- This is mainly because of changes in lifestyle, i.e. people are eating more processed food, doing less physical activity, and living longer.
- Diabetes is a common health problem that is increasing among both adults and children. In fact, India now ranks among the countries with the highest number of diabetes cases in the world. The disease usually develops due to a mix of factors such as hormonal imbalances, poor eating habits, lack of exercise, being overweight or obese, and other related causes.
Today, most deaths in India happen due to these diseases.
Dr. Kamal Ranadive (1917 – 2001) was a pioneering biomedical researcher from India. Her research explained how hormones and certain viruses are linked to cancer, leading to better ways of preventing and treating the disease. She also discovered that tobacco use, poor diet, and pollution increase cancer risk, highlighting why maintaining a healthy lifestyle is important.
Immunity : The Body’s Defence System
Our body has a natural defence system to fight diseases, known as immunity. This system prevents harmful microorganisms like bacteria, viruses, and fungi (called pathogens) from making us sick. People with weaker immune system tend to fall ill more often.
The immune system is made up of special cells, tissues, and organs that work together to protect the body from pathogens.
Types of Immunity
There are two main types of immunity
I. Innate Immunity
This is the body’s first line of defence, present from birth. It includes
• Skin, which acts as a physical barrier.
• Mucous membranes that trap germs in the nose and throat.
II. Acquired Immunity
When the body encounters a germ for the first time, it learns to recognise it. This ability to remember the germ and fight it better in the future is called acquired immunity.
This type of immunity is developed after recovering from a disease, or by getting vaccinated.
Role of Vaccines in Building Immunity
- Vaccination is one of the safest and most effective ways to develop acquired immunity without falling seriously ill.
Vaccines prepare the body’s immune system to recognise and fight specific germs if they attack in the future. - They work by introducing weakened or dead pathogens, or harmless parts of germs.
- Some newer vaccines instruct our own body cells to make harmless part of the germ, which our immune system then learns to fight.
- Once vaccinated, the body learns to detect and destroy the real germ quickly, preventing serious illness.
For example, the smallpox vaccine, developed by Edward Jenner, used the cowpox virus to build immunity against smallpox. - Similarly, modern vaccines like those for polio, measles, and COVID-19 protect millions of people worldwide.
- Vaccines protect people of all ages from serious diseases by preventing infections before they happen.
- They are preventive, not curative, and are carefully tested for safety. Getting vaccinated not only protects you but also helps safeguard your community.
Polio vaccine protects against poliomyelitis, a viral disease that can cause paralysis. It is given orally and is a key part of the global effort to eliminate polio. Regular vaccination
has helped India remain polio-free since 2014.
India’s Contribution to Vaccination
- India is a global leader in vaccine production, supplying life-saving vaccines worldwide. During the COVID-19 pandemic, Indian manufacturers played a crucial role in vaccine distribution.
- In ancient India, a traditional method called variolation was used to protect against smallpox. It involved applying material from a smallpox sore to a skin scratch, causing a mild infection to build immunity. Practitioners of this method were called teekedaars.
- Dr. Maharaj Kishan Bhan was a renowned Indian scientist who helped develop the Rotavirus vaccine, protecting children from diarrhoea. As Secretary of the Department of Biotechnology, he promoted affordable healthcare and advanced health and biotechnology sector in India.
Treatment of Diseases
- Even though our immune system and vaccines protect us from many diseases, sometimes these defences are not enough, and we fall ill. In such cases, medical treatment becomes necessary to help the body to fight infections and recover.
- When the disease is caused by a pathogen, such as bacteria, viruses, or protozoan, doctors prescribe different treatments based on the type of infection.
- Antibiotics are special medicines used to kill or stop the growth of bacteria. They are effective only against bacterial infections because they target parts of bacterial cells that are different from human cells.
- Traditional medicine systems like Ayurveda, Siddha, and Unani have also been used in India for many years to manage common health problems. They use natural substances like herbs, oils, and minerals for managing illnesses and promoting recovery, and focus on a healthy lifestyle and balanced diet. While these systems can help with some conditions, and are useful for everyday well-being, they may not be effective for all diseases and at all stages.
- But in all cases, rest, hydration, and a nutritious diet help the body’s natural healing process.
Antibiotics
These are the chemical substances produced mainly by microorganisms (bacteria and fungi). At low concentration they have the ability to inhibit the growth of other microorganisms. They commonly block the biochemical pathways important for bacteria, e.g. penicillin.
The first antibiotic, penicillin, was discovered by a bacteriologist from London, named Alexander Fleming in 1928. He observed that a mould growing on a petri dish released a substance that killed bacteria nearby. This discovery led to the development of penicillin, which saved millions of lives and became the first widely used antibiotic.
Antibiotics do not work against viral diseases like the common cold, flu, or COVID-19, nor against infections caused by protozoans. Other treatments, such as antiviral medicines or antiprotozoal drugs, are needed for those types of infections.
Antibiotic Resistance : A Growing Problem
Although antibiotics have helped control many diseases, using them carelessly can lead to a serious problem called antibiotic resistance. This happens when bacteria change and become strong enough to survive antibiotic treatment.
In any group of bacteria, a few may naturally resist antibiotics. When antibiotics are used, most bacteria die, but the resistant ones survive.
These resistant bacteria then multiply, creating a new group that antibiotics cannot kill.
Bacteria can also share resistance genes with other bacteria. Over time, the number of resistant bacteria increases, and they spread, making future infections much harder to treat.
Spread of Antibiotic Resistance
Once resistant bacteria develop, they can easily spread in different ways
- Human use Taking antibiotics when they are not needed, such as for colds or flu (which are viral diseases).
Not finishing the full course of antibiotics, allowing resistant bacteria to survive.
Self-medicating with leftover antibiotics. - Agricultural use Giving antibiotics to animals like chickens and cows to promote faster growth.
Resistant bacteria from animals can enter the food chain through meat and milk - Environmental spread Wastewater from hospitals and farms can carry resistant bacteria.
These bacteria can spread through crops, animal products, and poor sanitation, - Healthcare settings Hospitals can become breeding grounds for resistant bacteria.
Surfaces, tools, and hands of healthcare workers can carry resistant bacteria from one patient to another. Patients discharged from hospitals may carry resistant bacteria back to their communities.
Preventing Antibiotic Resistance
Antibiotic resistance can be controlled by following practices in both healthcare and daily life. The key preventive measures include
- Antibiotics should be taken only when prescribed by a qualified doctor.
- Antibiotics must not be used to treat viral infections such as colds, flu, or COVID-19.
- The full course of antibiotics should always be completed, even if the symptoms reduce before completion.
- Sharing antibiotics or using leftover medicines must be strictly avoided.
- Good hygiene practices, such as regular handwashing, help in preventing infections and reduce the need for antibiotics.
- Reducing the use of antibiotics in agriculture and animal farming also plays an important role in controlling resistance.
By following these measures, the spread of antibiotic-resistant bacteria can be minimised, ensuring that antibiotics remain effective for treating bacterial infections in the future.