9th Class Science Notes in English chapter 13 Why do we fall ill? 

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9th Class Science Notes in English chapter 13 Why do we fall ill? 


CBSE Revision Notes for CBSE Class 09 Science Why Do We Fall ill Why Do We Fall ill: Health and its failure. Infectious and Non-infectious diseases, their causes and manifestation. Diseases caused by microbes (Virus, Bacteria and Protozoans) and their prevention; Principles of treatment and prevention. Pulse Polio programmes.

Class 9th Science chapter 13 Why do we fall ill? Notes in English

📚 Chapter - 13 📚
👉 Why Do We Fall ill? 👈

9th Class Science Notes in English chapter 13 Why do we fall ill

✳️Introduction :-


🔹 According to WHO (World Health Organisation) health is a "state of physical, metal 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. 

✳️ Health :-

🔹 Health is a state of complete physical, mental and social wellbeing.


✳️Diseases :-

🔹 Any disturbance in the structure or function of any organ or part of body. The various causes of diseases are pathogens (virus, bacteria), lack of balanced diet or lack of public health services. 


✴️Difference b/w Being Healthy and Disease-Free

9th Class Science Notes in English chapter 13 Why do we fall ill

✳️ Types of Disease :- 


⭐ Diseases are basically of two types. 

✴️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 and Non-infectious Diseases 


✴️Infectious Diseases : 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, fungi worms. 

✴️Non-infectious Diseases : The disease which does not spread by contact between infected and healthy person through air and water, is called non-infectious disease. E.g., Arthritis, heart disease.

9th Class Science Notes in English chapter 13 Why do we fall ill


✳️ 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. 
9th Class Science Notes in English chapter 13 Why do we fall ill

✴️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 organisms like female anopheles mosquito also work as a vector of disease, like malaria, dengue, yellow fever etc.


✴️Through sexual contact : Syphilus, 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. 


✳️AIDS (Acquired Immuno Deficiency Syndrome) 

🔹 It is caused by a retro-virus called HIV (Human Immuno Deficiency Virus). It get transmitted from an infected to a healthy person through sexual contact, blood transfusion, use of infected needle or blade etc.


✳️Antibiotics :-  


🔹 These are the chemicals (medicine, drugs) that block biochemical pathways important for bacterial. They are used for diseases caused by bacteria. 

🔹 Antibiotics do not work against viral infections as the viruses do not have their own biochemical mechanisms but depend upon that of the host.


✳️ORGAN – Specific and Tissue-specific Manifestations 

⭐ Disease causing microbes enter the body by different means and goes to different organs and tissues. 

🔹 Microbes which enter through the nose are likely to go to the lungs. (Bacteria which cause tuberculosis of lungs). 

🔹 Microbes which enter through the mouth are likely to stay in the gut (bacteria which causes typhoid) or liver (bacteria which causes jaundice) 

🔹 Virus which causes Japanese encephalitis (brain fever) enters the body through mosquito bite and goes and infects the brain.

9th Class Science Notes in English chapter 13 Why do we fall ill


✳️ 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 our energy. 

✴️To kill the microbes: This can be done by taking suitable antibiotics and drugs which kills the microbes and the disease is cured.


✳️Principles of Prevention 

✴️1. General method: 

🔹 They involve (a) Preventing exposure against microbes (b) By boosting the immune system 

⭐ (a) Preventing exposure against microbes can be done in following ways: 

🔹 i. For air-born microbes we can prevent exposure by avoiding overcrowded places. For water-borne microbes we can prevent exposure by not using contaminated water. 

🔹 ii. For vector-borne infections we can prevent exposure by providing clean enyironment.


⭐ (b) By boosting the immune system: 

🔹 Our immune system plays an important role in fighting against the microbes that enter our body. strengthening the immune system can help in preventing many diseases. 

🔹 So, proper nourishment or healthy diet that includes all the necessary nutrients as well as vitamins and minerals is necessary for better functioning of our immune system.


✴️2. Specific method: 

🔹 It involves the prevention method directed against a particular disease. 

🔹 It is done by immunisation which is the process of introducing a weakened pathogen inside the body of the host to make his/her immune system to produce antibodies against that particular disease so that the 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.


✴️3. 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.

9th Class Science Notes in English chapter 13 Why do we fall ill

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