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Rivision Notes of Class 9th Science

Chapter :-13. Why do we fall ill

• Health :- It is a state of complete physical,social and mental well being.

In other words Health is a state of well being enough to function physically, socially and mentally well.

For example- An individual is healthy if he is physically,socially and mentally well.

             Health is not just the absence of disease.

The condition necessary for good Health :- i) Good physical and social environment it includes clean surrounding,good sanitation,proper garbage disposal and supply of clean drinking water.

ii) Good economic conditions includes job opportunities for earning to have nutritious food and to lead a healthy life.

   

Significance of Good Health :-  1) Good health promotes the efficiency for doing work.

2) It encourage happy and cheerful attitude.

3) it makes living a joyful experience.

4) It gives the ability to cope up with social and mental pressure without any great difficulty.

Disease :- It is a condition of disturbed functioning of the body or its part.

The misfunctioning of any tissue,organ or organ system will cause discomfort  i.e. will cause disease.As the disease is internal,the reason or the cause cannot be immediately known. Hence, a disease is diagnosed with the help of Symptoms and Signs.

Symptoms of a disease are things that we feel as being 'wrong'  with our body.

Example:- Headache,loose motion and cough etc.

Signs of disease are objective evidence of a disease that physicians(doctors) look for on the basis of the symptoms.Signs will give a more definite indication of the presence.

Disease literally means being uncomfortable.(dis - without ; ease - comfort)

  Difference between healthy and disease-free state

Healthy	Disease-free state
It is a state of complete physical,mental and social well being.	It is a state of absence of discomfort in any part of the body.
It depends upon the individual as well as physical and social environment.	It is related to individual only.

Types of disease -

Classification Based on the infectious agents :-

1) Bacterial Disease:- The disease which are caused by bacteria are called bacterial disease. Example:- TB, Typhoid,Cholera,Anthrax, etc.

2) Protozoan Disease:- Are the disease which are caused by Protozoa.

Example:-Malaria, sleeping sickness,Kala azar,etc

3)Fungal Disease:- Are  the disease which are caused by fungi.

Example:- Ringworm disease,skin infections,etc.

4)Viral Disease:- Are the disease which are caused by viruses.

Example:- AIDS,Rabies,common cold,etc.

5) Helminthic Disease:- Are the disease which are caused by helminths(worms). Example:- ascariasis,elephantiasis,etc.

Classification Based on the portal off entry:- Portal of entry can be defined as the pathways by which infectious agents or organisms gain access into the body.

1) Gastrointestinal tract : Disease in which the pathogen enters the body through the gastrointestinal tract  i.e.via mouth.

2) Respiratory tract : Disease in which the pathogen enters the body through the respiratory tract.

3)Urinogenital tract : Disease in which the pathogen enters the body through the Urinogenital tract.

4)Skin : Disease in which the pathogen enters the body through the skin like mosquito bite or cuts in skin.

Classification Based on the duration of disease:-

 1) ACUTE Disease :- i) It lasts for a short time.

ii) It doesn't cause major effects on general health.

iii) The patient gets recovered within few days after the treatment.

iv) Examples of acute disease are:- diarrhoea,cold,cough etc. 

2) CHRONIC Disease :- i) It is a longer duration disease.

ii) Being of long duration,a person is likely to have prolonged poor health.

iii) The recovery is seldom complete even after treatment.

iv) Examples of chronic disease are :- TB(tuberculosis,diabetes,asthma etc.

Classification Based on whether the disease is by birth or not:-

1) CONGENITAL Disease:- These diseases are  present since birth.These are the abnormalities caused due to abnormal chromosome number, abnormal chromosome structure, misfunctioning of gene ,organ or any metabolic pathways.

For Example :- Colour blindness, haemophilia Down's syndrome etc.

2)   ACQUIRED Disease :- These diseases are  picked up after birth. 

Example :- diabetes, cold,cough, diarrhoea etc.

Acquired disease are further classified as follows :-

i) INFECTIOUS or COMMUNICABLE Disease :-  These disease are caused by disease causing microorganisms or pathogens i.e. Bacteria, protozoa,fungi, viruses and worms etc.

It is communicated from diseases person to healthy person.

For Example:- TB, malaria, diarrhoea etc.

ii) NON-INFECTIOUS Disease :- These disease are not caused by any infectious agents or microorganism.These are mostly due to internal non- infectious causes.

For Example:-  Cancer, heart disease  etc.

     

CAUSES OF DISEASE :- 

DISEASE CAUSED BY:-

i) Pathogen like viruses,bacteria,fungi,protozoa and worms
ii) Hereditary and genetic disorders

iii)  Lack of proper sanitation,clean surrounding and clean drinking water.