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CBSE Class 9 Answered

give me the summary of the lesson
 
Asked by paddipawar | 21 Nov, 2014, 09:51: PM
answered-by-expert Expert Answer
The chapter "Why do we fall ill" summarizes about health of the body and the different types of diseases.
Health and Disease.
1. Health - A state of physical, mental, and social well-being that includes a unity and harmony within the mind, body, and soul of an organism
2. Disease - Any condition that can lead to discomfort, distress, health problems, and  even death of the affected person
Symptoms - Indications of disease, such as headache, stomach pain, nausea, etc that can only be felt by the patient 
3. Causes of diseases
4. Types-  Acute and Chronic
Acute - Lasts for a short period of time, eg. Cold, cough, influenza, etc.
Chronic - Lasts for long periods of time, eg. Diabetes, kidney stones, etc.
5. On the basis of causative agents - Infectious and Non-infectious
Infectious - Diseases such as influenza, cold, etc., which are caused due to infectious agents 
Non-infectious - Diseases such as high blood pressure, cancer, etc., which are caused by some internal causes such as excessive weight, genetic defects, etc.
6. Viruses - These are tiny organisms that grow, multiply, or reproduce only inside the host cells
Diseases caused by viruses - Influenza, cold (Rhinovirus), dengue, AIDS, SARS etc.
7. Bacteria - These are unicellular organisms; larger than viruses
Diseases caused by bacteria - Whooping cough, typhoid, cholera, anthrax, etc.
8. Fungi - These are plant-like organisms; heterotrophic
Diseases caused by Fungi - Athlete’s foot, candidiasis, ringworms
9. Protozoa - These are simple, primitive unicellular organisms which are often found in water
Diseases caused by Protozoa - Amoebiasis, kala azar, malaria, African sleeping sickness, etc. 
10. Multicellular animals like worms - These are parasites that infect the intestines of human beings and other animals
Diseases caused by worms- Diarrhoea, etc.
11. Communicable diseases- An infectious disease is classified as communicable disease when it can be transferred from an infected person to a healthy person
12. Means of disease spread
They are the disease-causing microorganisms which belong to different categories such as- Air-borne diseases - Transmitted when disease-causing microorganisms are 
expelled into the air by coughing, sneezing, talking, etc. E.g. common cold, chicken 
pox, small pox, pneumonia, influenza, tuberculosis, etc. and Water-borne diseases - Spreads when the excretions (from an infected person)
containing causal microorganisms get mixed with drinking water and this contaminated water is consumed. E.g. cholera, typhoid, hepatitis A, etc.
13. Physical contact – Includes sexually-transmitted diseases. E.g. syphilis, gonorrhoea, AIDS, etc.
14. Blood to blood contact – Such contact is established during blood transfusion or pregnancy (between the mother and her baby). E.g. AIDS can spread through blood contact
15. Prevention of diseases
Antigens - Foreign substances that invade our body
Immunisation - The protection of the body from communicable diseases by administration of some agent that mimics the microbe.
Vaccine: The suspension of killed microbes that mimics the disease causing microbes. 
Vaccines available against tetanus, polio, measles, hepatitis B, etc
Answered by Sivanand Patnaik | 22 Nov, 2014, 09:07: PM
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