Why Do We Fall Ill Notes | Class 9 CBSE Science Notes

Important Notes of Why Do  We Fall ill

Health: It is a state of complete physical mental and social well being, not merely an absence of disease. Good Health constitutes a healthy body with healthy mind as well as healthy attitude.
 It renders an individual happy and cheerful
Makes living a joyful experience.
 Increases efficiency for all the activities of life

Factors that affect the Health of an individual
 a)physical environment
b)Social environment
c)Mental state of an individual
 d)Economic Conditions

 The community and the environment in which an individual lives directly affect the health of an individual.Community health care provisions involve Clean and safe drinking water Efficient system for disposal of garbage, sewage and rainwater Medical care facilities Educating the people to make them understand the ways of keeping good health

 Disease is a improper functioning of body organs due to one or the other reason The word disease literally means absence of comfort or not being at ease In the diseased state, either form or function of one or more part of the body gets altered.

Changes in form or functions appear as symptoms and sigsn of the disease.
Symptoms of the disease are changes and the feeling that make an individual uncomfortable Different diseases manifest same symptoms like fever,headache,cough and loose motions.

Signs of the disease are changes that indicate a specific cause A symptom can be defined as one of the characters of a disease. Meanwhile, sign is the definite indication of a specific disease.

Physicians diagnose diseases on the basis of the specific signs and symptoms and confirm on the basis of laboratory tests

On the basis of duration of occurrence, the diseases are classified into two categories
ACUTE Disease:
 It lasts for very short period of time for e.g common cold
 Patient recovers completely after the cure
There is no loss of weight or feeling of tiredness
afterward
There is short duration loss of work and
efficiency


 Chronic Disease:
It persist for long time even as much as life time e.g elephantiasis.
Patient does not recover completely
There is often loss of weight of feeling of
tiredness
There is a prolonged loss of work and efficiency


Causes of Diseases : Most of the diseases have many causes, rather than one single
cause, like unclean water, nourishment, genetic differences, genetic abnormalities e.g.
Based on the causes diseases are of two types: Non-Infectious Diseases and Infectious
Diseases.

Diseases are caused due to
a)infection by microorganisms like bacteria,virus fungi, protozoa, and worms
b).Malnutrition i.e. deficiency of one or more nutrients
c).Contaminated water and air
d).Malfunctioning of different body organs
e).Genetic disorder

Immediate cause of Disease:
The agent that causes the disease is called immediate cause e.g. if a person gets jaundice, the immediate cause is virus infection

Contributory causes are factors that lend support to immediate cause to be able to cause the disease
Contaminated water is the source of infection.
He suffers from lack of resistance
He lacks resistance because he does not get proper nourishment


Infectious Diseases: Caused by infectious agents.
Infectious disease causing organism are transmitted from a sick person to healthy person by direct contant, air , water, and carriers and vectors

Group of organisms and diseases caused by them.

The signs and symptoms of the disease depend on the tissue or organs where microorganism enter and attack

• Symptoms appear due to activation of the body's immune system in response to infection.
• Activated immune system sends white blod cells to the affected tissues to fight the germs
• It causes inflammation visible in the form of rashes swelling and pain in the infected area
• Rise in body temperature may also occur. 

There are two approaches for the treatment of infectious disease
a)to reduce the harmful effects of the disease
b) To kill the casual organism of disease

Principles of Treatment:
1. Antibiotics- many bacteria make a cell wall to protect themselves, the antibiotic (Penicillin) blocks the bacterial process that builds cell wall and blocks the biochemical pathways. Antibiotics do not work against viral infections. Antiviral medicine is harder than making Antibacterial medicine because Virus has only few biochemical mechanisms of their own. Other medicines bring down fever, reduce pain or loose motions. We can take bed rest to conserve energy.

Viruses do not have cellular organisation
They enter our cells and use our cellular machinery for their life processes
As they have few biochemical mechanisms of their own it is difficult to make anti viral medicine

Principles of Prevention :
Following three limitation are normally confronted while
treating an infectious disease:
 Once someone has disease, their body functions are damaged and may never
recover completely.
 Treatment will take time, which means that someone suffering from a disease is
likely to be bedridden for some time even if we can give proper treatment.
 The person suffering from an infectious disease can serve as the source from where
the infection may spread to other people.

General ways of preventing infectious disease :
 Air-borne – We can prevent exposure by providing living condition that are not
overcrowded.
 Water-borne – prevent by providing safe drinking water. This is done by treating the
water to kill any microbial contamination.
 Vector-borne – We can provide clean environment, which would not allow mosquito
breeding.

Immunity: Even in cells there is repair mechanism called” Immunity”. Immune cells
manage to kill off the infectious agents. Smallpox disease is eliminated by developing
memory cells for particular infection by mimics the microbes, called” Vaccine”. The basis of
Immunization- if you had smallpox once, there was no chance of suffering from it again.
Proper nutrition is essential to maintain body immunity. There are vaccines against tetanus,
diphtheria, whooping cough, measles, polio and many other diseases.

Immunisation can be active or passive
Active immunisation:When the body produces anti bodies to fight against infection for which vaccination is done

Passive Immunisation:When readymade anti bodies are directly injected to provide protection