Class 9 Science Chapter 13 Why Do We Fall ill Notes

9 Class Science Chapter 13 Why Do We Fall ill Notes

TextbookNCERT
ClassClass 9
SubjectScience
Chapter Chapter 13
Chapter NameWhy Do We Fall ill
CategoryClass 9 Science Notes
MediumEnglish

Class 9 Science Chapter 13 Why Do We Fall ill Notes. here we will be learn about Diseases and its types, Individual and community health, Acute diseases, Chronic diseases, Infectious diseases, Non-communicable diseases, Causes of disease, Various microorganisms, Treatment of disease, Prevention of disease , general methods , disease specific methods etc.

Class 9 Science Chapter 13 Why Do We Fall ill Notes

📚 Chapter = 13 📚
💠 Why Do We Fall ill 💠

❇️ Health :-

🔹 Health is a general condition of a person’s mind and body.

🔹 ‘Health’ is a state of being well enough to function well physically, mentally and socially.

🔶 According to WHO (World Health Organisation) :- health is a “state of physical, mental and social well-being of a person”.

🔹 To make people aware and conscious of keeping healthy and disease-free we celebrate WORLD HEALTH DAY on 7th April every year.

❇️ Good health has following advantages :-

🔹 It increases our working efficiency & helps us to perform various activity at our best. 

🔹 It helps us to cope up with the social & mental pressure without much difficulty. 

🔹 It makes our life joyful.

❇️ The conditions necessary for good health are :-

🔶 Good physical and social environment :- Good physical and social environment includes clean surroundings, good sanitation, proper garbage disposal and clean drinking water.

🔶 Good economic conditions :- Good economic conditions includes job opportunities for earning to have nutritious food and to lead a healthy life. 

🔶 Active life style :- Active life style includes regular exercise and health conscious attitude.

❇️ Community Health :-

🔹 It refers to maintenance, protection and improvement of whole community in which an individual lives.

❇️ Personal and Community Issues Both Matter for Health :-

  • Personal and community health are supplementary to each other. 
  • We protect ourselves by keeping our body clean. 
  • For this, we also require a good and healthy environment in our surroundings. 
  • We can have this only by the means of community health and development. 
  • So, both personal and community health are inter-related.

❇️ Differences between Being Healthy and Disease-free :-

Being Healthy Being Disease-free 
It is a state of being well enough to function well physically, mentally and socially. It is a state of absence from diseases. 
It refers to the individual, physical and social environment. It refers only to the individual.
The individual has good health EnergeticThe individual may have good health or poor health.

❇️ Diseases :-

🔹 It refers to any condition that disturbs or modifies the normal functioning of the living organisms.

❇️ What does disease look like ? 

🔹 When a person is affected by a disease either the functioning or the appearance of one or more systems of the body will change for the worse.

🔹 These changes give rise to symptoms and signs of disease. 

🔹 On the basis of the symptoms the physicians look for the signs of a particular disease and conduct tests to confirm the disease.

❇️ Signs of Diseases :-

🔹 It gives more definite indications of the presence of a particular disease it include laboratory test, ultrasound etc.

🔶 Symptoms of Diseases :-

🔹 Symptoms of diseases are the indications that we feel as being wrong, such as cold, headache, loose motion etc.

❇️ Diseases are caused by :-

  • Pathogens like virus, bacteria, fungi, protozoans or worms. 
  • Poor health and under nourishment. 
  • Hereditary and genetic disorder. 
  • Lack of proper treatment immunization. 
  • Environmental pollution (air, water etc.)

❇️ Types of Diseases :-

🔶 Acute Diseases :- 

🔹 Acute diseases which last for only very short period of time and affect body suddenly and quickly. 

🔹 E.g :- Cold, cough, typhoid etc. 

🔶 Chronic Diseases :-

🔹 The diseases which last for a long time, even as much as a life time, are called chronic diseases. 

🔹 E.g :- Diabetes, tuberculosis, elephantiasis etc. 

🔶 Infectious Disease Communicable :-

🔹 The diseases which spread due to infection by micro-organisms are called infectious diseases. It is communicated from diseased person to healthy person, caused by some biological agents/pathogens like viruses, bacteria, fungi, protozoans, worms.

🔹 e.g :- corona, T.B etc.

🔶 Non-infectious Diseases – Non Communicable :-

🔹 The diseases which does not spread by contact between infected and healthy person through air and water, is called non-infectious disease. 

🔹 E.g :- Arthritis, heart diseases, Diabetes, Hyper Thyroids etc.

  • Deficiency diseases :- caused due to deficiency of nutrient. eg. goitre etc. 
  • Degenerative diseases :- ex. arthritis. 
  • Allergies 
  • Cancer :- Leukemia 

🔶 Congenital diseases :- The diseases present since birth, caused due to genetic abnormalities or defective development of embryo. 

🔹 e.g :- haemophilic.

❇️ Difference between Infectious & Non-infectious disease :-

Infectious/CommunicableNon-infectious/Non- Communicable 
These disease spread from one person to another. These do not spread from one person to another. 
These are caused due to pathogens like viruses, bacteria These could be caused due deficiency, cancer, degeneration, injury or metabolic disorders 
May be chronic & acute Primary by chronic nature.
for eg :- common cold, T.B. etc for e.g :- Kwashiorkar, cancer etc.

❇️ Pathogens :-

🔹 The disease causing organisms are called pathogens. These can also be known as infections agents.

❇️ Categories of infectious agents are :-

🔶 Bacteria (e.g., Salmonella typhi, Micobacterium tuberculi, Staphylococcus etc. 

🔶 Fungi :- Posinous mushrooms, 

🔶 Protozoan :- Amoeba, Trypanosoma, Plasmodium, Leishmania)

🔶 Worm :- Ascaris etc. 

❇️ Epidemic diseases :-

🔹 Some infectious diseases that develop and spread rapidly to many people in a community are called epidemic diseases. 

🔹 e.g :- corona virus.

❇️ Means of Spread of Infectious Diseases :-

🔹 Infectious diseases spread from an infected person to a healthy person through air, water, food, vectors, physical contact and sexual contact. 

🔶 Through air :- By sneezing and coughing, the microbes spread into air and enter into the body of a healthy person, like common cold, tuberculosis, pneumonia etc. 

🔶 Through water :- The microbes enter into our body by drinking/eating polluted and contaminated water/food, like cholera, amoebic dysentery etc.

🔶 Vectors :- Some infected organisms like Dog, Cat, Monkey & Mosquito (female anopheles mosquito) spread the diseases to a healthy person when they bite them like Rabies malaria, dengue, yellow fever etc. 

🔶 Through sexual contact (STD) :- Syphilis, AIDS spread by sexual contact with infected person. AIDS virus can also spread through blood transfusion and from the mother to her child during pregnancy and through breast feeding.

🔶 Through physical contact :- Some disease spread when we use the clothes food etc. used by infected person e.g., Scabies, Fungal infection etc. 

❇️ AIDS :-

🔹 (Acquired Immuno Deficiency Syndrome) 

🔶 Causes :- 

🔹 AIDS is caused by a retro-virus called HIV (Human Immuno Deficiency Virus).

🔶 Method of transmission of AIDS :- 

🔹 The transmission of AIDS from an infected to a healthy person takes place :-

  • through sexual contact 
  • blood transfusion 
  • use of infected needle or blade etc. 
  • This may also get transmitted from infected mother to her foetus.

🔶 Prevention :-

  • Avoid transfusion of infected blood. 
  • This can be done by testing whether the blood is HIV negative or not. 
  • Always use disposable needle and syringe. 
  • Avoid sexual contact with unknown person. 
  • Avoid the same razor used in the salons.

❇️ ORGAN – Specific and Tissue – specific Manifestations :-

🔹 Disease causing microbes enter the body by different means and goes to different organs and tissues. The signs & symptoms of a disease will depend on the tissue, organ which the Microbes Target. 

  • (i) Microbes which enter through the nose are likely to go to the lungs. (Bacteria which cause tuberculosis of lungs). 
  • (ii) Microbes which enter through the mouth are likely to stay in the gut (bacteria which causes typhoid) or liver (bacteria which causes jaundice). 
  • (iii) Virus which causes AIDS enter the body through sexual organs during sexual contact and spread through the lymph to all parts of the body and damages the immune system.
  • (iv) Virus which causes Japanese encephalitis (brain fever) enters the body through mosquito bite and goes and infects the brain. 

❇️ Principles of Treatment :-

🔹 The treatment of infectious diseases consists of two steps. They are to reduce the effects of the disease (symptoms) and to kill the microbes which caused disease. 

🔶 To reduce the effects of the disease :- This can be done by taking medicines to bring down the effects of the disease like fever, pain or loose motions etc. and by taking bed rest to conserve energy.

🔶 To kill the microbes :- This can be done by taking suitable antibiotics and drugs which kills the microbes and the disease incurred.

❇️ How to cure disease :-

🔹 To cure disease specific medicine are used to kill that microbes, some medicines are : Anti bacterial

❇️ Antibiotic :-

🔹 These drugs are used to kill or stop the growth of bacteria in the body. These drugs are very specific means they and work only against bacterial infections. ex :- Pencilline, Tetracycline, Cefixime etc. 

🔹 Antibiotics acts by blocking some biochemical pathways that are important for bacterial growth like many bacteria make cell wall after division protect themselves but the Antibiotics block the pathway that is required to build cell wall and thus bacteria dies & diseases is cured. 

🔹 As these biochemical pathways are different for different microbes. Thus these medicines only work against a particular categories of microbes and not on other.

  • Antiviral medicine :- These drugs are used against viral infections. 
  • Antifungal medicine :- These drugs are used only against fungal infections. 
  • Antiprotozoal medicine :- These drugs are used only against protozoal infections.
  • Antihelminthic medicine :- These medicines can used to treat infections as caused by parastic worms.

❇️ Principles of Prevention :-

  • “Prevention is better than its cure “. 

🔹 There are two ways of prevention of infectious diseases :-

  • General ways of prevention
  • Specific ways of prevention

❇️ General ways of prevention :-

  • Public & Personal hygiene and Balanced Diet are most important for prevention of infectious diseases. 
  • Proper and sufficient food for everyone will make people healthy to resist the infection.

🔹 Air borne diseases can be prevented by living in conditions that are not crowded. 

  • Water borne diseases can be prevented by providing safe drinking water. 
  • Vector borne diseases can be prevented by providing clean environment.

❇️ Specific ways of prevention :-

🔹 There are disease specific measures which are used to fight them. It is done by Immunisation. This is the process of introducing a weakened pathogen inside the body of the host to fool his/her immune system to produce antibodies against particular disease.

🔹 Not only does our that immune system fight the disease (feeble pathogen), but also keeps a memory of the incident by keeping those antibodies in blood. Thus, next time even if the disease will strike the host’s body with full vigor, the body will be able to protect itself with the help of these antibodies. This is also the basic law followed by vaccination programmes done for infants.

❇️ Vaccination :-

🔹 Vaccination is the administration of a vaccine to help the immune system develop protection from a disease. Vaccines contain a microorganism in a weekend or killed non infective state.

❇️ Vaccines available against are :-

🔹 Tetanus, diphtheria, whooping cough, measles, polio, BCG. [Bacillus Calmette Guerin) used against prevention of TB] 

🔹 The small pox vaccine was invented in 1796 by Edward Jenner.

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