Chapter Notes - Why do we fall ill Class 9 Notes | EduRev

Science Class 9

Created by: Dr Manju Sen

Class 9 : Chapter Notes - Why do we fall ill Class 9 Notes | EduRev

The document Chapter Notes - Why do we fall ill Class 9 Notes | EduRev is a part of the Class 9 Course Science Class 9.
All you need of Class 9 at this link: Class 9

1. Health is not merely the absence of diseases. It is a state of complete physical, mental and social well being.
2. Health of a person depends upon one’s personal habits as well as physical and social environment.
3. A disease is a condition of the body or a part of it in which functions are disturbed or damaged.
4. Diseases are diagnosed with the help of symptoms and signs.
5. Symptoms are manifestations or evidence of the presence of diseases. They are in the form of structural and functional changes in the body or body parts. On the basis of symptoms, physicians search for definite signs of the disease. The cause of disease can be found by tests etc.
6. Diseases can be mild or serious. On the basis of duration, serious disease can be acute or chronic.
7. Acute disease is a short duration disease which generally has a relatively severe course. Being of short duration an acute disease is unable to cause major effect on health.
Example: Common cold, malaria, typhoid, diarrhoea.
8. Chronic disease is a long duration disease which generally develops slowly with a milder course in the beginning. It builds up with time. Due to prolonged duration, it damages the affected organ. There is often a loss of weight accompanied by feeling of tiredness. Examples : Tuberculosis and diabetes.
9. Diseases can also be classified into two categories depending on the time it gets inflicted, namely congenital and acquired.
10. Congenital diseases are the diseases that are present since birth either due to defective development of embryo or defective inheritance.
Examples: Haemophilia, colour blindness, hare lip, hole in the heart etc.
11. Acquired diseases are those diseases which are picked up after birth. Depending upon their ability or inability to spread from one individual to another acquired diseases are of two kinds, infectious and non-infectious.
12. Infectious (communicable) diseases are caused by microbes and other pathogens such as bacteria, fungi, viruses, protozoans, worms etc., which spread the infection from diseased person to healthy person by means of air, water, food, insects (vectors), physical and sexual contact.
13. Non-infectious (Non-communicable) diseases are diseases caused by factors other than living pathogen. They cannot pass from one person to another except for hereditary diseases where it occurs from parent to offspring. High blood pressure, diabetes, goitre are a few examples of non-communicable diseases.
14. The various causes of diseases are pathogens, lack of nutritious diet and lack of public health services.
15. The infectious agents are bacteria, viruses, fungi, protozoans and helminths. The infectious agents may attack the same organ where they have entered or they may enter some other organ.
16. The disease causing microbes enter the body through different means i.e., through nose, mouth, genital openings or through blood stream (wounds).
17. In most cases the infected organ or tissue-specificity depends upon the portal of entry. Disease will spread in the body only when the microbe enters the body in sufficient number.
18. Some of the common effects of infectious diseases are fever, inflammation, diarrhoea etc.
19. There are two principles of treatment:
(i) Killing the microbe and
(ii) Reducing the effect of the disease
20. We kill microbes by using antibiotics. Antibiotics are certain chemicals obtained from a group of microorganisms that kill or retard the growth of another microbe.
21. Antibiotics such as penicillin blocks the process of cell wall formation in growing bacteria as a result of which they cannot multiply and ultimately die.
22. Viruses do not form a cell wall or use such pathways and hence antibiotics do not work against viruses. Despite this limitation there are now effective antiviral drugs available in the market; for example, drugs that keep HIV infection under control.
23. There are two ways to prevent infection namely general and specific. We can prevent infection by general practices like proper hygiene, nutrition, exercise and relaxation.
24. Specific ways to prevent infection is to get the immunisation or vaccination.
25. Vaccines are heat killed or chemically weakened germs which when injected in our body develops memory for a particular infection in our body It stimulates the formation of antibodies by the immune system which prevents any subsequent exposure to the infecting microbe from turning into an actual disease.
26. Vaccines are available against number of diseases such as tetanus, diphtheria, whooping cough, measles, polio, hepatitis and so on.
27. Typhoid, cholera, tuberculosis, diphtheria, anthrax, tetanus and acne are a few examples of bacterial diseases.
28. Diseases caused by viruses are common cold, influenza, polio, dengue fever, measles, chickenpox, AIDS and SAKS.
29. Malaria, sleeping sickness, kala-azar are some of the protozoal diseases.
30. Multicellular heterotrophic fungi cause ring worm, athlete’s foot and other skin infections.
31. Examples of diseases caused by helminthal worms are taeniasis (by tapeworm), ascariasis (by roundworm), elephantiasis (by filarial worm, hence also known as filariasis) etc.

Offer running on EduRev: Apply code STAYHOME200 to get INR 200 off on our premium plan EduRev Infinity!

Complete Syllabus of Class 9

Dynamic Test

Content Category

Related Searches

Objective type Questions

,

Extra Questions

,

mock tests for examination

,

Important questions

,

Exam

,

ppt

,

video lectures

,

Viva Questions

,

Free

,

shortcuts and tricks

,

Sample Paper

,

past year papers

,

Summary

,

Chapter Notes - Why do we fall ill Class 9 Notes | EduRev

,

Chapter Notes - Why do we fall ill Class 9 Notes | EduRev

,

study material

,

MCQs

,

pdf

,

practice quizzes

,

Previous Year Questions with Solutions

,

Semester Notes

,

Chapter Notes - Why do we fall ill Class 9 Notes | EduRev

;