Why do we fall ill
1) Our body’s well-being is dependent on the proper functioning of its cells and tissues.
2) All our body parts and activities are greatly interconnected. Hence dysfunction of any body part will affect the entire body.
3) When we are healthy, we are able to perform our physical, mental and social functions well.
4) Our physical and social environment plays an important role in maintaining good health.
5) In addition to personal hygiene, public cleanliness should also be maintained for ensuring that we remain healthy.
6) Many other factors like financial conditions, availability of nutritious food and social equality also influence the health of an individual.
7) A person suffering from a disease is in a state of discomfort.
8) Being in poor health is different from being diseased.
9) Symptoms and signs of the disease appear as a result of dysfunction of the affected body parts. These help to identify the disease that a person is suffering from.
10) Depending on their duration, diseases may be classified as acute or chronic.
11) Acute diseases last for a short time and do not cause major health effects. E.g. Common cold. On the other hand chronic diseases persist for a long time and hence cause prolonged ill health. E.g. TB of lungs.
12) Causes of diseases may be immediate (first level cause) or contributory. For e.g. – The immediate cause of a person suffering from
diarrhoea is the causative agent. The contributory causes could be
i) lack of good nourishment or genetic difference (second level cause), ii) poverty or lack of public services (third level cause)
13) Diseases may be infectious or non-infectious. Infectious diseases are caused by microbes or other infectious agents (e.g. Malaria) whereas noninfectious diseases have internal, non-infectious causes (e.g. High blood pressure).
14) The infectious agents may be viruses, bacteria, fungi, protozoans or multicellular organisms like worms.
Category of infectious agent | Examples of diseases caused |
Virus | Common cold, influenza, Dengue fever, AIDS |
Bacteria | Typhoid, cholera, tuberculosis, anthrax |
Fungi | Skin infections |
Protozoans | Malaria, kala-azar |
Worms | Intestinal worm infections, elephantiasis |
15) The type of treatment of a disease depends on the category of the infectious agent.
16) Organisms belonging to one category will share several important life processes, which will be different from those of organisms belonging to other categories.
17) Drugs working by interfering with life processes of one category of organisms will not be effective against members of another category. E.g. Antibiotics act against bacteria, but not viruses, since viruses do not share bacterial pathways.
18) Penicillin interferes with bacterial cell wall production, thus killing the bacteria. Due to lack of cell walls, penicillin does not affect human cells.
19) Many infectious diseases are called ‘communicable diseases’ since they can spread from one person to another.
20) Communicable diseases can spread through air, water, food, sexual contact or vectors.
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NCERT 9 Science