RBSE Class 9 Science Notes Chapter 13 Why Do We Fall Ill

These comprehensive RBSE Class 9 Science Notes Chapter 13 Why Do We Fall Ill will give a brief overview of all the concepts.

RBSE Class 9 Science Chapter 13 Notes Why Do We Fall Ill

→ According to WHO, ‘Health is a state of complete physical, mental and social well being’.

→ Health is considered as the state of perfect functioning of body and mind.

→ Significance of Good Health :

• Good health increases working efficiency of a person.
• ‘It leads to personal progress as well as the society.
• Good health gives cheerfulness and positive attitude towards life.

→ Personal and community issues both matter for health.

Personal Health	Community Health
1. Individual based.	Community based.
2. Involves good physical, mental and social well-being of an individual.	Comprises improving, maintaining and protesting the health of other community.
3. Can be maintained by taking healthy balanced diet, pure drinking water, domestic and personal hygiene.	Can be maintained by cleanliness of surroundings, proper disposal of sewage, sanitary conditions, etc.

→ Difference between being healthy and disease free :

Healthy	Disease free
1. It is a state of physical, mental and social well-being.	It is a state when body is free from any discomfort or symptoms of any disease.
2. A healthy person will be free from disease.	A disease free person may or may not be healthy.
3. A healthy person is energetic and functions at its full biological potential.	Disease free person may or may not be able to perform to its full biological potential.

→ Disease word is formed by two terms : Dis + ease, i.e. without ease or comfort. Disease is the malfunctioning of the organism or a part of it due to infection, inherent weakness or environmental stress that upsets the normal physiological functioning of the organism.

→ A disease is identified by its signs and symptoms. It can be caused by internal or external factors.

→ Diseases are basically of two types : Acute disease and Chronic disease.

Acute Disease	Chronic Disease
1. Disease that last for short period oftime.	Diseases that is long lasting, sometimes for lifelong.
2. There is no loss of weight or feeling of tiredness afterward.	There is often loss of weight or feeling of tiredness.
3. The symptoms appear suddenly.	Have drastic long term effect.
4. Patient recovers completely after cure.	Patient does not recover completely.
5. Example – Influenza, Common cold, etc.	Exmaple – TB, Cancer, etc.

→ Causes of disease : Most of the disease have many causes, rather than one cause, like nourishment, unclean water, genetic abnormalities, genetic differences, etc.

→ Based on the causes, diseases are of two types : Non-infectious and infectious diseases.

Non-infectious diseases	Infectious diseases
1. Caused by factors other than pathogens.	Caused by disease causing microorganisms.
2. Internal or intrinsic.	External or extrinsic.
3. No transmission except hereditary disease.	Through contaminated air, water or food, direct contact or through vector.
4. Community hygiene plays no role in their control.	Community hygiene can reduce incidences of occurence.
Example – Arthritis, blood pressure, cardiac disease, etc.	Example – Cold, cough, influenza, cholera, smallpox, etc.

→ Two Australians, Robin Warren (1937) and Barry Marshall (1951) made a discovery that a bacterium, Helicobacter phylosi, was responsible for peptic ulcers. They showed that patients could be cured of peptic ulcer only when the bacteria were killed off from the stomach.

→ Infectious agents : Pathogens or microbes that cause infectious diseases are called infectious agents.

→ Drugs that block one of these life processes in one member of group is likely to be effective against many other members of the group, but the same drug will not work against a microbe belonging to a different group.

→ Many bacteria, make a cell-wall to protect themselves, antibiotics block the bacterial process of building the cell-wall and biochemical pathways. But they do not work against viral infections. Making antiviral medicine is harder than making antibacterial medicine because virus has only few biochemical mechanisms of their own.

→ Means of Spread : Infectious diseases spread by agents from an infected person to healthy person which are called communicable diseases.

(i) Air borne diseases : The diseases which are transmitted through air in the form of droplet in the air are known as air borne diseases, e.g. common cold, tuberculosis, pneumonia, etc.

(ii) Water borne diseases : Diseases which spread through water are known as water borne diseases, e.g. cholera, typhoid, dysentery, etc.

(iii) Sexually transmitted diseases : AIDS, syphilis spread through 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. (iv) Vector borne diseases: Many diseases are transmitted by other animals. These animals carry the infecting agents from a sick person to another potential host.

These animals are called vectors, e.g. Rabbis, Malaria (through mosquitoes).

→ 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 mouth are likely to stay in gut (bacteria which causes typhoid) or liver (bacteria which causes jaundice).
• Microbes which enter through nose are likely to go to the lungs (bacteria which causes tuberculosis of lungs).
• Virus which causes japanese encephalitis (brain fever) enters into the body through mosquito bite and goes and infects the brain.
• 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.

→ An active immune system recruits many cells to the affected tissue to kill off the disease – causing microbes and this recruitment process is called inflammation.

→ There are two ways to cure any disease :

• Reduce the effects of disease by providing treatment.
• Kill the cause of disease by using medicines that kill microbes.

→ Principles of Preventation : There are two ways to prevent any disease :

(A) General ways of prevention :

• Public hygiene is an important way to prevent diseases.
• Air-borne diseases can be prevented by avoiding going out to crowded places, covering mouth and nose while sneezing and coughing.
• Water-borne diseases can be prevented by using safe and clean drinking water.
• Vector-borne diseases can be prevented by maintaining clean surroundings.

(B) Specific ways of prevention :

• Immunisation : Methods to strengthen the defence mechanism of body against infection.
• Vaccination : Use of vaccine to stimulate the immune system against specific pathogens.

→ A vaccine can be of following types :

• Killed pathogen (Example – Vaccine for whooping cough)
• Live but weakened pathogen (Example – BCG vaccine, polio vaccine)
• Modified toxins (Example – Tetanus vaccine)
• Isolated antigens (Example – Flu vaccine)
• Genetically, engineered antigens (Exmaple – Hepatitis B vaccine)