REVISION NOTES

1. WHY DO WE FALL ILL (class IX BIOLOGY)
HEALTH:
It is a state of complete physical mental and social well being and not merely the absence of disease or infirmity in a
human being
PHYSICAL HEALTH MENTAL HEALTH SOCIAL HEALTH
It is the normal state of structure
and proper functioning of the body
parts. It can be assessed by
different tests.
 It is a state of normal mental
satisfaction, which is
achieved when the
individual maintains a
balance with its
environment
 A mentally sound individual
can contribute to his or her
society or community in a
better way
 Mental health cannot be
measured
 It is the happiness of an
individual at home, work place
and society
 It cannot be measured
FACTORS INFLUENCING HEALTH
 Heredity
 Environmental
 Socio- economic ( employment, education, and income)
 Personal hygiene, habits, behavior
 Psychological
IMPORTANCE OF HEALTH
 Good health makes living a joyful experience
 Good health increases our efficiency for doing wok
 Good health is a pre-condition for our purposeful existence.

2. CONDITIONS ESSENTIAL FOR GOOD HEALTH
Proper sanitation of the environment
Providing pure drinking water
Control of communicable diseases
School health schemes
Some other activities of community health
National programs
National malaria
eradication programme
National filarial control
progamme
National smallpox
eradication programme
National leprosy
control programme
National cholera
control programme
Tuberculosis
programme
Pulse polio programme
for the eradication of
polio
Personal cleanliness
Nutrition
Physical exercise
Rest, sleep and relaxation
PERSONAL HEALTH (Hygiene) COMMUNITY HEALTH (Hygiene)

3. Distinction between Healthy and disease free
HEALTHY DISEASE FREE
It is a state of complete physical, mental and social well
being
It is a state of absence of discomfort or in any part of the
body
It depends upon the individual as well as on physical and
social environmental factors
It is related to the individual only
A healthy person will be disease free A disease free person can be healthy or unhealthy
Helathy person is energetic and able to perform as per
requirement
Performance of a disease free person depends upon
environment and personal attitude.
DISEASE:
Any condition, which impairs the health or interferes with the normal functioning of the body due to one or the
other reason, is called Disease
SYMPTOMS SIGNS
They indicates the presence of diseases Signs indicates the presence of a particular disease
These are the evidences of the presence of diseases of
various body parts
These are the specific for each disease.
Symptoms may include headache, cough, loose motions, etc. the symptoms include that there is something wrong
with the body but they do not indicate what disease it may be. For example, a head ache may be due to stress, or
lack of sleep or worse, meningitis.
On the basis of symptoms, signs of diseases can be found out by physicians. The signs of disease give some more
indication of a particular disease. On the basis of the signs, Laboratory tests can be conducted to diagnose the exact
disease. For example, in case of persistent pain in leg, X-ray and vitamin-D/ Calcium tests can be conducted.
ACUTE DISEASES CHRONIC DISEASES
The disease which last for very short periods of time are
called acute diseases
The diseases that last for a long time, even as much as a
life time, are called chronic diseases
There are no bad effects on our general health Have long term bad effects on our general health, such
as loss of weight, short breath, tiredness, etc
Do not reduce our ability to learn May reduce our ability to learn
For example cough, common cold, diarrhea. For example, tuberculosis, elephantiasis, leprosy, etc.
CAUSES OF DISEASES (agents and factors which produce the diseases)
IMMEDIATE CAUSE CONTRIBUTING CAUSES THIRD LEVEL OF CAUSES
(first level of cause) (Secondary causes)
(Primary cause)
Pathogens Under nourishmen 1. Poor public health services
Poor health (Repeated supply of unclean water)
2. Poverty

4. For example, if few babies are suffering from loose motions, we can say that an immediate cause of infections or
disease is a virus. Such immediate causes of diseases are called FIRST LEVEL CAUSES. At this juncture we may ask
that from where these viruses come? The answer would be that the virus came from unclean drinking water. We
may think why few babies develop loose motions after drinking unclean water in the society. One reason might be
that in comparison to others, these few Babies are not healthy and therefore, are likely to get the disease when
exposed to risk. Our study may result in question why are these few babies not healthy? The answer would be that
perhaps these are under fed (not well nourished).Thus; lack of good nourishment becomes SECOND LEVEL
CAUSE OFTHE DISEASE that babies suffering from. Therefore, poor public services providing unclean drinking water
in the region where such babies are living in society and poverty becomes the THIRD LEVEL CAUSE OF THE DISEASE
TYPES OF DISEASES
CONGENTIAL ACQUIRED
NON COMMUNICABLE COMMUNICABLE
(Non- infectious) (Infectious)
CONTAGIOUS NON-CONTAGIOUS
DEGENERATIVE DEFICIENCY DISEASES ALLERGIES CANCER
TYPES OF DISEASES
Based on the time of their occurrence-whether from birth or after birth, diseases are broadly grouped into two
categories:
CONGENITAL DISEASES:
 Those diseases which are present since birth are called congenital diseases.
 These diseases are caused due to genetic abnormality or malfunctioning of any organ or organ system
 These diseases are permanent, generally not easily curable and may be passed on from one generation to
another.
Examples-Haemophilia, colour blindness, sickle cell anemia, Down’s syndrome and albinism.

5. COLOUR BLINDNESS
SICKEL CELL ANEMIA DOWNS SYSNDROM
ALBINISM

6. ACQUIRED DISEASES
 Those diseases which develop after birth are called acquire diseases.
 These can be broadly classified into two types.
1. communicable or infectious diseases
2. Non- communicable or non-infectious diseases.
1. COMMUNICABLE OR INFECTIOUS DISEASES
 Those diseases spread from an unhealthy or infected person to a healthy person
 They are caused by microorganisms (pathogen) such as viruses, bacteria, fungi, protozoa or
helminths (worms)
 The causative organism of the disease can spread form one person to another through
contact, water, air, food, etc
TYPE OF PATHOGEN Common diseases caused by them
Viruses Common cold, influenza, measles, mumps,
poliomyelitis, rabies, smallpox, chickenpox,
yellow fever, AIDS.
Bacteria Cholera, typhoid, tuberculosis, tetanus,
diphtheria, pneumonia, syphilis, gonorrhoea,
leprosy, anthrax etc.
Rickettsiae Typhus fever, tick fever
Protozoa Malaria, amoebic dysentery, sleeping
sickness, kala azar
Fungi Ringworm, athletes foot
Worms Filaria, ascariasis, cysticercosis, taeniasis,
2. NONCOMMUNICABLE DISEASES
 These diseases do not spread from an infected person to a health person
 They are caused due to some specific factors such as malfunctioning of some vital organs
and deficiency of nutrients.
 Non communicable diseases can be further divided into
Degenerative diseases-
These diseases are caused due to malfunctioning of important body organs
Examples- kidney failure, heart diseases
Deficiency diseases-
These diseases are caused by the deficiency of nutrients in our diet like proteins, minerals,
vitamins, etc.
Examples-Marasmus, kwashiorkor, anaemia, goitre, beriberi and pellagra.
Allergies
 Allergy is caused due to the hypersensitivity of the body to foreign substances like
pollen grains, dust, silk, nylon, egg, fish and certain drugs
 The substances due to which allergy is caused are called allergens.
Example- asthma, bronchitis and skin allergy, hay fever
Cancer
It is caused due to the uncontrolled growth and mortification of certain tissue in the body

7. Depending upon the extent of occurrence, the diseases are grouped into four categories
(i) Endemic-
These diseases are found in certain area only attacking a fewer number of people
Examples- Yellow fever in certain African countries.
(ii) Epidemic-
These diseases break out and spread from place to place affecting large number of people.
Examples- Plague in India in 1994
(iii) Pandemic-
When the disease spreads throughout the world
Examples- AIDS
(iv) Sporadic-
When there are scattered individual cases of disease.
METHODS OF TRANSMISSION (SPREAD OF DISEASES)
DIRECT TRANSMISSION INDIRECT TRANSMISSION
(i) Direct contact (i) Carriers or vectors
Examples- chicken pox, small pox, measles Housefly- Cholera, typhoid, dysentery,
(ii) Droplet infection Female Anopheles mosquito- malaria
Examples- common cold, Head louse- Typhus
Influenza, diphtheria, T.B, Pneumonia (i) Vehicle- borne methods
(iii) Contact with soil- Tetanus Food, water, ice, blood- cholera, typhoid, AIDS
(iv) Animal bites- Rabies (III) Air-borne methods
(v) Trans placental transmission- From mother to foetus air and dust- typhus
Examples- German measles, syphilis Garments’, toys, handkerchief, towels,
(iv) Unclean hands

11. Anopheles culex
aedes

12. SOME EXAMPLES OF COMMUNICABLE DISEASES
Name
Of the
disease
Causative
pathogen
Modes of
transmission
Prevention Treatment
Malaria Plasmodium Female anopheles
mosquito
Prevent
mosquitoes from
biting
 Quinine (bark of tree cinchona)
 Central drug research institute
(CDRI) has developed an anti
cerebral malarial drug called
–Arteether (Artemisia annua)
 Synthetic drugs Chloroquine
phosphate
Primaquine


14. NAME OF
THE
DISEASE
CAUSATIVE
AGENT
MODE OF TRANSMISSION HOW ONE DOES NOT GET THE HIV
INFECTION
AIDS HIV or HTLV
III or LAV
 Intimate sexual contact
 Through blood transfusion
 Contaminated needles and syringes
 Through organ transplantation
 From mother to child during
pregnancy
 Close contact between infected and
healthy persons through cuts and
wounds.
It does not spread by mere physical
touch, sharing food, kissing, mosquito
bites, shaking hands.
SYMPTOMS DETECTION PREVENTION CONTROL /
TREATMENT
 Flu like illness
 Weight loss
 Fever
 Los of appetite
 Diarrhoea
 Unexpected bleeding
 Loss of memory
And mental ability
 Brain damage
Swollen lymph nodes
Decreased count of
blood platelets
Causing
haemorrhages
 Patient becomes
susceptible to other
infections due to
breakdown of immune
system
 ELISA test and
Western blot
test are used for
the detection of
AIDS
 HIV positive
person can be
identified
through blood
test by detecting
the presence of
anti-HIV
antibodies in the
blood of patient.
 Education of the masses
 Use of disposable syringes
and needles
 Avoiding sexual
intercourse with strangers
 Using condoms during
intercourse
 Testing the blood before
transfusion
 Accepting organ for
transplantation from non
HIV positive person
 Routine check-up by the
Government agencies for
detecting HIV positive
persons.
There is no cure for
AIDS so far

15. NAME OF THE
DISEASE
CAUSATIVE AGENT Who will get SYMPTOMS SCIENTISTS
Peptic ulcers Helicobacter pylori Stressful life style led
to led to a lot of acid
secretion in the
stomach cause
peptic ulcers
Painful bleeding
areas in stomach and
duodenum
Rabin warren and
Bary Marshall
(were awarded
Nobel prize in 2005)

16. Process of disease
there are four stages in the process of disease
1. INFECTION The entry of a disease-causing organisms into our body is called infection
2. INCUBATION  This is the time between the entry of the disease-causing organism into the body
and the appearance of the sickness.
 During infection, only few diseases organisms will be able to enter the body of the
host
 This small number of disease causing organisms is not sufficient to cause any
disease of the host
 They select a suitable tissue in the body of the host and settle down in the tissue
 They get their requirements from the host tissue and divide multiply very rapidly
and increase in number
3. MANIFESTATION The appearance of the symptoms is called manifestation of disease
4. TERMINATION In this stage, the disease process is halted either temporarily or permanently
ORGAN SPECIFIC AND TISSUE SPECIFIC MANIFESTATION
POINT OF ENTRY TARGET
ORGANS
SYMPTOMS EXMAPLE
From air through the nose lungs Cough ,, breathlessness Tuberculosis
Mouth Lining of gut Typhoid
Mouth Liver Jaundice
Through anus (sexual
contact)
Lymph nodes AIDS
through mosquito bite Liver and RBC Malaria
through mosquito bite Brain Headache, vomiting, fits or
unconsciousness
Japanese encephalitis or
brain fever
INFLAMATION
 An active immune system recruits many cells to the affected tissue to destroy the disease causing microbes.
This recruitment process is called inflammation.
 As a part of this process, there are local effects such as swelling and pain, and general effects such as liver
PRINCIPLES OF TRREATMENT (There are two ways to treat an infectious disease)
By reducing the effect of disease by killing the cause of the disease
1. Medicine Medicines (Antibiotics)
2. Take bed rest

17. PRINCIPLES OF PREVENTION
HYGIENIC CONDITIONS PROPER AND SUFFICIENT FOOD IMMUNISATION