NCERT Textbook - Why do we fall ill? Class 9 Notes | EduRev

NCERT Textbooks (Class 6 to Class 12)

: NCERT Textbook - Why do we fall ill? Class 9 Notes | EduRev

 Page 1


Activity _____________13.1
• We have all heard of the earthquakes in
Latur, Bhuj, Kashmir etc. or the cyclones
that lashed the coastal regions. Think
of as many different ways as possible in
which people’s health would be affected
by such a disaster if it took place in our
neighbourhood.
• How many of these ways we can think of
are events that would occur when the
disaster is actually happening?
• How many of these health-related events
would happen long after the actual
disaster, but would still be because of the
disaster?
• Why would one effect on health fall into
the first group, and why would another
fall into the second group?
When we do this exercise, we realise that
health and disease in human communities
are very complex issues, with many
interconnected causes. We also realise that
the ideas of what ‘health’ and ‘disease’ mean
are themselves very complicated. When we
ask what causes diseases and how we prevent
them, we have to begin by asking what these
notions mean.
We have seen that cells are the basic units
of organisms. Cells are made of a variety of
chemical substances–proteins, carbo-hydrates,
fats or lipids, and so on. Cell is a dynamic place.
Something or the other is always happening
inside them. Complex reactions and repair goes
on inside cells. New cells are being made. In
our organs or tissues, there are various
specialised activities going on– the heart is
beating, the lungs are breathing, the kidney
is filtering urine, the brain is thinking.
All these activities are interconnected. For
example, if the kidneys are not filtering urine,
poisonous substances will accumulate. Under
such conditions, the brain will not be able to
think properly. For all these interconnected
activities, energy and raw material are needed.
Food is a necessity for cell and tissue functions.
Anything that prevents proper functioning of
cells and tissues will lead to a lack of proper
activity of the body.
It is in this context that we will look at the
notions of health and disease.
13.1 Health and its Failure
13.1.1 THE SIGNIFICANCE OF ‘HEALTH’
We have heard the word ‘health’ used quite
frequently. We use it ourselves as well, when
we say things like ‘my grandmother’s health
is not good’. Our teachers use it when they
scold us saying ‘this is not a healthy attitude’.
What does the word ‘health’ mean?
If we think about it, we realise that it
always implies the idea of ‘being well’. We can
think of this well-being as effective
functioning. For our grandmothers, being able
to go out to the market or to visit neighbours
is ‘being well’, and not being able to do such
things is ‘poor health’. Being interested in
following the teaching in the classroom so that
we can understand the world is called a
‘healthy attitude’; while not being interested
is called the opposite. ‘Health’ is therefore a
state of being well enough to function well
physically, mentally and socially.
13.1.2 PERSONAL AND COMMUNITY ISSUES
BOTH MATTER FOR HEALTH
If health means a state of physical, mental and
social well-being, it cannot be something that
13
W W W W WHY HY HY HY HY D D D D DO O O O O W W W W WE E E E E F F F F FALL ALL ALL ALL ALL I I I I ILL LL LL LL LL? ? ? ? ?
Chapter
2020-21
Page 2


Activity _____________13.1
• We have all heard of the earthquakes in
Latur, Bhuj, Kashmir etc. or the cyclones
that lashed the coastal regions. Think
of as many different ways as possible in
which people’s health would be affected
by such a disaster if it took place in our
neighbourhood.
• How many of these ways we can think of
are events that would occur when the
disaster is actually happening?
• How many of these health-related events
would happen long after the actual
disaster, but would still be because of the
disaster?
• Why would one effect on health fall into
the first group, and why would another
fall into the second group?
When we do this exercise, we realise that
health and disease in human communities
are very complex issues, with many
interconnected causes. We also realise that
the ideas of what ‘health’ and ‘disease’ mean
are themselves very complicated. When we
ask what causes diseases and how we prevent
them, we have to begin by asking what these
notions mean.
We have seen that cells are the basic units
of organisms. Cells are made of a variety of
chemical substances–proteins, carbo-hydrates,
fats or lipids, and so on. Cell is a dynamic place.
Something or the other is always happening
inside them. Complex reactions and repair goes
on inside cells. New cells are being made. In
our organs or tissues, there are various
specialised activities going on– the heart is
beating, the lungs are breathing, the kidney
is filtering urine, the brain is thinking.
All these activities are interconnected. For
example, if the kidneys are not filtering urine,
poisonous substances will accumulate. Under
such conditions, the brain will not be able to
think properly. For all these interconnected
activities, energy and raw material are needed.
Food is a necessity for cell and tissue functions.
Anything that prevents proper functioning of
cells and tissues will lead to a lack of proper
activity of the body.
It is in this context that we will look at the
notions of health and disease.
13.1 Health and its Failure
13.1.1 THE SIGNIFICANCE OF ‘HEALTH’
We have heard the word ‘health’ used quite
frequently. We use it ourselves as well, when
we say things like ‘my grandmother’s health
is not good’. Our teachers use it when they
scold us saying ‘this is not a healthy attitude’.
What does the word ‘health’ mean?
If we think about it, we realise that it
always implies the idea of ‘being well’. We can
think of this well-being as effective
functioning. For our grandmothers, being able
to go out to the market or to visit neighbours
is ‘being well’, and not being able to do such
things is ‘poor health’. Being interested in
following the teaching in the classroom so that
we can understand the world is called a
‘healthy attitude’; while not being interested
is called the opposite. ‘Health’ is therefore a
state of being well enough to function well
physically, mentally and socially.
13.1.2 PERSONAL AND COMMUNITY ISSUES
BOTH MATTER FOR HEALTH
If health means a state of physical, mental and
social well-being, it cannot be something that
13
W W W W WHY HY HY HY HY D D D D DO O O O O W W W W WE E E E E F F F F FALL ALL ALL ALL ALL I I I I ILL LL LL LL LL? ? ? ? ?
Chapter
2020-21
healthy. Social equality and harmony are
therefore necessary for individual health. We
can think of many other such examples of
connections between community issues and
individual health.
each one of us can achieve entirely on our own.
The health of all organisms will depend on
their surroundings or their environment. The
environment includes the physical
environment. So, for example, health is at risk
in a cyclone in many ways.
Human beings live in societies. Our social
environment, therefore, is an important factor
in our individual health. We live in villages,
towns or cities. In such places, even our
physical environment is decided by our social
environment.
Consider what would happen if no agency
is ensuring that garbage is collected and
disposed. What would happen if no one takes
responsibility for clearing the drains and
ensuring that water does not collect in the
streets or open spaces?
So, if there is a great deal of garbage
thrown in our streets, or if there is open drain-
water lying stagnant around where we live,
the possibility of poor health increases.
Therefore, public cleanliness is important for
individual health.
Activity _____________13.2
• Find out what provisions are made by
your local authority (panchayat/
municipal corporation) for the supply
of clean drinking water.
• Are all the people in your locality able
to access this?
Activity _____________13.3
• Find out how your local authority
manages the solid waste generated in
your neighbourhood.
• Are these measures adequate?
• If not, what improvements would you
suggest?
• What could your family do to reduce
the amount of solid waste generated
during a day/week?
We need food to be healthy, and this food
will have to be earned by doing work. For this,
the opportunity to do work has to be available.
We need to be happy in order to be truly
healthy, and if we mistreat each other and are
afraid of each other, we cannot be happy or
WHY DO WE FALL ILL? 177
13.1.3 DISTINCTIONS BETWEEN ‘HEALTHY’
AND ‘DISEASE-FREE’
If this is what we mean by ‘health’, what do we
mean by ‘disease’? The word is actually self-
explanatory – we can think of it as ‘disease’ –
disturbed ease. Disease, in other words,
literally means being uncomfortable. However,
the word is used in a more limited meaning.
We talk of disease when we can find a specific
and particular cause for discomfort. This does
not mean that we have to know the absolute
final cause;  we can say that someone is
suffering from diarrhoea without knowing
exactly what has caused the loose motions.
We can now easily see that it is possible to
be in poor health without actually suffering
from a particular disease. Simply not being
diseased is not the same as being healthy.
‘Good health’ for a dancer may mean being
able to stretch his body into difficult but
graceful positions. On the other hand, good
health for a musician may mean having enough
breathing capacity in his/her lungs to control
the notes from his/her flute. To have the
opportunity to realise the unique potential in
all of us is also necessary for real health.
The Five ‘F’s — What is to be done?
Protect the water source (H)
Treat and store water
safely (S)
Wash hands before preparing and
taking food (H)
Wash hands after defecation (S)
Cover the food (H)
Control flies (S)
Clean vegetables and fruits before
use (H)
Avoid open defecation (S)
Proper drainage system (H)
Treatment of water (S)
Prevention of Transmission of Diseases by Maintaining
Sanitation and Hygiene
Hygiene
Sanitation
Healthy person Faecal matter
2020-21
Page 3


Activity _____________13.1
• We have all heard of the earthquakes in
Latur, Bhuj, Kashmir etc. or the cyclones
that lashed the coastal regions. Think
of as many different ways as possible in
which people’s health would be affected
by such a disaster if it took place in our
neighbourhood.
• How many of these ways we can think of
are events that would occur when the
disaster is actually happening?
• How many of these health-related events
would happen long after the actual
disaster, but would still be because of the
disaster?
• Why would one effect on health fall into
the first group, and why would another
fall into the second group?
When we do this exercise, we realise that
health and disease in human communities
are very complex issues, with many
interconnected causes. We also realise that
the ideas of what ‘health’ and ‘disease’ mean
are themselves very complicated. When we
ask what causes diseases and how we prevent
them, we have to begin by asking what these
notions mean.
We have seen that cells are the basic units
of organisms. Cells are made of a variety of
chemical substances–proteins, carbo-hydrates,
fats or lipids, and so on. Cell is a dynamic place.
Something or the other is always happening
inside them. Complex reactions and repair goes
on inside cells. New cells are being made. In
our organs or tissues, there are various
specialised activities going on– the heart is
beating, the lungs are breathing, the kidney
is filtering urine, the brain is thinking.
All these activities are interconnected. For
example, if the kidneys are not filtering urine,
poisonous substances will accumulate. Under
such conditions, the brain will not be able to
think properly. For all these interconnected
activities, energy and raw material are needed.
Food is a necessity for cell and tissue functions.
Anything that prevents proper functioning of
cells and tissues will lead to a lack of proper
activity of the body.
It is in this context that we will look at the
notions of health and disease.
13.1 Health and its Failure
13.1.1 THE SIGNIFICANCE OF ‘HEALTH’
We have heard the word ‘health’ used quite
frequently. We use it ourselves as well, when
we say things like ‘my grandmother’s health
is not good’. Our teachers use it when they
scold us saying ‘this is not a healthy attitude’.
What does the word ‘health’ mean?
If we think about it, we realise that it
always implies the idea of ‘being well’. We can
think of this well-being as effective
functioning. For our grandmothers, being able
to go out to the market or to visit neighbours
is ‘being well’, and not being able to do such
things is ‘poor health’. Being interested in
following the teaching in the classroom so that
we can understand the world is called a
‘healthy attitude’; while not being interested
is called the opposite. ‘Health’ is therefore a
state of being well enough to function well
physically, mentally and socially.
13.1.2 PERSONAL AND COMMUNITY ISSUES
BOTH MATTER FOR HEALTH
If health means a state of physical, mental and
social well-being, it cannot be something that
13
W W W W WHY HY HY HY HY D D D D DO O O O O W W W W WE E E E E F F F F FALL ALL ALL ALL ALL I I I I ILL LL LL LL LL? ? ? ? ?
Chapter
2020-21
healthy. Social equality and harmony are
therefore necessary for individual health. We
can think of many other such examples of
connections between community issues and
individual health.
each one of us can achieve entirely on our own.
The health of all organisms will depend on
their surroundings or their environment. The
environment includes the physical
environment. So, for example, health is at risk
in a cyclone in many ways.
Human beings live in societies. Our social
environment, therefore, is an important factor
in our individual health. We live in villages,
towns or cities. In such places, even our
physical environment is decided by our social
environment.
Consider what would happen if no agency
is ensuring that garbage is collected and
disposed. What would happen if no one takes
responsibility for clearing the drains and
ensuring that water does not collect in the
streets or open spaces?
So, if there is a great deal of garbage
thrown in our streets, or if there is open drain-
water lying stagnant around where we live,
the possibility of poor health increases.
Therefore, public cleanliness is important for
individual health.
Activity _____________13.2
• Find out what provisions are made by
your local authority (panchayat/
municipal corporation) for the supply
of clean drinking water.
• Are all the people in your locality able
to access this?
Activity _____________13.3
• Find out how your local authority
manages the solid waste generated in
your neighbourhood.
• Are these measures adequate?
• If not, what improvements would you
suggest?
• What could your family do to reduce
the amount of solid waste generated
during a day/week?
We need food to be healthy, and this food
will have to be earned by doing work. For this,
the opportunity to do work has to be available.
We need to be happy in order to be truly
healthy, and if we mistreat each other and are
afraid of each other, we cannot be happy or
WHY DO WE FALL ILL? 177
13.1.3 DISTINCTIONS BETWEEN ‘HEALTHY’
AND ‘DISEASE-FREE’
If this is what we mean by ‘health’, what do we
mean by ‘disease’? The word is actually self-
explanatory – we can think of it as ‘disease’ –
disturbed ease. Disease, in other words,
literally means being uncomfortable. However,
the word is used in a more limited meaning.
We talk of disease when we can find a specific
and particular cause for discomfort. This does
not mean that we have to know the absolute
final cause;  we can say that someone is
suffering from diarrhoea without knowing
exactly what has caused the loose motions.
We can now easily see that it is possible to
be in poor health without actually suffering
from a particular disease. Simply not being
diseased is not the same as being healthy.
‘Good health’ for a dancer may mean being
able to stretch his body into difficult but
graceful positions. On the other hand, good
health for a musician may mean having enough
breathing capacity in his/her lungs to control
the notes from his/her flute. To have the
opportunity to realise the unique potential in
all of us is also necessary for real health.
The Five ‘F’s — What is to be done?
Protect the water source (H)
Treat and store water
safely (S)
Wash hands before preparing and
taking food (H)
Wash hands after defecation (S)
Cover the food (H)
Control flies (S)
Clean vegetables and fruits before
use (H)
Avoid open defecation (S)
Proper drainage system (H)
Treatment of water (S)
Prevention of Transmission of Diseases by Maintaining
Sanitation and Hygiene
Hygiene
Sanitation
Healthy person Faecal matter
2020-21
SCIENCE 178
So, we can be in poor health without there
being a simple cause in the form of an
identifiable disease. This is the reason why,
when we think about health, we think about
societies and communities. On the other
hand, when we think about disease, we think
about individual sufferers.
uestions
1. State any two conditions essential
for good health.
2. State any two conditions essential
for being free of disease.
3. Are the answers to the above
questions necessarily the same or
different? Why?
13.2 Disease and Its Causes
13.2.1 WHAT DOES DISEASE LOOK LIKE?
Let us now think a little more about
diseases. In the first place, how do we know
that there is a disease? In other words, how
do we know that there is something wrong
with the body? There are many tissues in
the body, as we have seen in Chapter 6.
These tissues make up physiological
systems or organ systems that carry out
body functions. Each of the organ systems
has specific organs as its parts, and it has
particular functions. So, the digestive
system has the stomach and intestines, and
it helps to digest food taken in from outside
the body. The musculoskeletal system,
which is made up of bones and muscles,
holds the body parts together and helps the
body move.
When there is a disease, either the
functioning of one or more systems of the body
will change for the worse. These changes give
rise to symptoms and signs of disease.
Symptoms of disease are the things we feel as
being ‘wrong’. So we have a headache, we have
cough, we have loose motions, we have a
wound with pus; these are all symptoms.
These indicate that there may be a disease, but
they don’t indicate what the disease is. For
example, a headache may mean just
examination stress or, very rarely, it may
mean meningitis, or any one of a dozen
different diseases.
Signs of disease are what physicians will
look for on the basis of the symptoms. Signs
will give a little more definite indication of the
presence of a particular disease. Physicians will
also get laboratory tests done to pinpoint the
disease further.
13.2.2 ACUTE AND CHRONIC DISEASES
The manifestations of disease will be different
depending on a number of factors. Some
diseases last for only very short periods of time,
and these are called acute diseases. We all know
from experience that the common cold lasts
only a few days. Other ailments can last for a
long time, even as much as a lifetime, and are
called chronic diseases. An example is the
infection causing elephantiasis, which is very
common in some parts of India.
Activity _____________13.4
• Survey your neighbourhood to find out:
(1) how many people suffered from
acute diseases during the last
three months,
(2) how many people developed
chronic diseases during this same
period,
(3) and finally, the total number of
people suffering from chronic
diseases in your neighbourhood.
• Are the answers to questions (1) and
(2) different?
• Are the answers to questions (2) and
(3) different?
• What do you think could be the
reason for these differences? What do
you think would be the effect of these
differences on the general health of
the population?
13.2.3CHRONIC DISEASES AND POOR
HEALTH
Acute and chronic diseases have different
effects on our health. Any disease that causes
poor functioning of some part of the body will
affect our health. This is because all functions
of the body are necessary for being healthy.
Q
2020-21
Page 4


Activity _____________13.1
• We have all heard of the earthquakes in
Latur, Bhuj, Kashmir etc. or the cyclones
that lashed the coastal regions. Think
of as many different ways as possible in
which people’s health would be affected
by such a disaster if it took place in our
neighbourhood.
• How many of these ways we can think of
are events that would occur when the
disaster is actually happening?
• How many of these health-related events
would happen long after the actual
disaster, but would still be because of the
disaster?
• Why would one effect on health fall into
the first group, and why would another
fall into the second group?
When we do this exercise, we realise that
health and disease in human communities
are very complex issues, with many
interconnected causes. We also realise that
the ideas of what ‘health’ and ‘disease’ mean
are themselves very complicated. When we
ask what causes diseases and how we prevent
them, we have to begin by asking what these
notions mean.
We have seen that cells are the basic units
of organisms. Cells are made of a variety of
chemical substances–proteins, carbo-hydrates,
fats or lipids, and so on. Cell is a dynamic place.
Something or the other is always happening
inside them. Complex reactions and repair goes
on inside cells. New cells are being made. In
our organs or tissues, there are various
specialised activities going on– the heart is
beating, the lungs are breathing, the kidney
is filtering urine, the brain is thinking.
All these activities are interconnected. For
example, if the kidneys are not filtering urine,
poisonous substances will accumulate. Under
such conditions, the brain will not be able to
think properly. For all these interconnected
activities, energy and raw material are needed.
Food is a necessity for cell and tissue functions.
Anything that prevents proper functioning of
cells and tissues will lead to a lack of proper
activity of the body.
It is in this context that we will look at the
notions of health and disease.
13.1 Health and its Failure
13.1.1 THE SIGNIFICANCE OF ‘HEALTH’
We have heard the word ‘health’ used quite
frequently. We use it ourselves as well, when
we say things like ‘my grandmother’s health
is not good’. Our teachers use it when they
scold us saying ‘this is not a healthy attitude’.
What does the word ‘health’ mean?
If we think about it, we realise that it
always implies the idea of ‘being well’. We can
think of this well-being as effective
functioning. For our grandmothers, being able
to go out to the market or to visit neighbours
is ‘being well’, and not being able to do such
things is ‘poor health’. Being interested in
following the teaching in the classroom so that
we can understand the world is called a
‘healthy attitude’; while not being interested
is called the opposite. ‘Health’ is therefore a
state of being well enough to function well
physically, mentally and socially.
13.1.2 PERSONAL AND COMMUNITY ISSUES
BOTH MATTER FOR HEALTH
If health means a state of physical, mental and
social well-being, it cannot be something that
13
W W W W WHY HY HY HY HY D D D D DO O O O O W W W W WE E E E E F F F F FALL ALL ALL ALL ALL I I I I ILL LL LL LL LL? ? ? ? ?
Chapter
2020-21
healthy. Social equality and harmony are
therefore necessary for individual health. We
can think of many other such examples of
connections between community issues and
individual health.
each one of us can achieve entirely on our own.
The health of all organisms will depend on
their surroundings or their environment. The
environment includes the physical
environment. So, for example, health is at risk
in a cyclone in many ways.
Human beings live in societies. Our social
environment, therefore, is an important factor
in our individual health. We live in villages,
towns or cities. In such places, even our
physical environment is decided by our social
environment.
Consider what would happen if no agency
is ensuring that garbage is collected and
disposed. What would happen if no one takes
responsibility for clearing the drains and
ensuring that water does not collect in the
streets or open spaces?
So, if there is a great deal of garbage
thrown in our streets, or if there is open drain-
water lying stagnant around where we live,
the possibility of poor health increases.
Therefore, public cleanliness is important for
individual health.
Activity _____________13.2
• Find out what provisions are made by
your local authority (panchayat/
municipal corporation) for the supply
of clean drinking water.
• Are all the people in your locality able
to access this?
Activity _____________13.3
• Find out how your local authority
manages the solid waste generated in
your neighbourhood.
• Are these measures adequate?
• If not, what improvements would you
suggest?
• What could your family do to reduce
the amount of solid waste generated
during a day/week?
We need food to be healthy, and this food
will have to be earned by doing work. For this,
the opportunity to do work has to be available.
We need to be happy in order to be truly
healthy, and if we mistreat each other and are
afraid of each other, we cannot be happy or
WHY DO WE FALL ILL? 177
13.1.3 DISTINCTIONS BETWEEN ‘HEALTHY’
AND ‘DISEASE-FREE’
If this is what we mean by ‘health’, what do we
mean by ‘disease’? The word is actually self-
explanatory – we can think of it as ‘disease’ –
disturbed ease. Disease, in other words,
literally means being uncomfortable. However,
the word is used in a more limited meaning.
We talk of disease when we can find a specific
and particular cause for discomfort. This does
not mean that we have to know the absolute
final cause;  we can say that someone is
suffering from diarrhoea without knowing
exactly what has caused the loose motions.
We can now easily see that it is possible to
be in poor health without actually suffering
from a particular disease. Simply not being
diseased is not the same as being healthy.
‘Good health’ for a dancer may mean being
able to stretch his body into difficult but
graceful positions. On the other hand, good
health for a musician may mean having enough
breathing capacity in his/her lungs to control
the notes from his/her flute. To have the
opportunity to realise the unique potential in
all of us is also necessary for real health.
The Five ‘F’s — What is to be done?
Protect the water source (H)
Treat and store water
safely (S)
Wash hands before preparing and
taking food (H)
Wash hands after defecation (S)
Cover the food (H)
Control flies (S)
Clean vegetables and fruits before
use (H)
Avoid open defecation (S)
Proper drainage system (H)
Treatment of water (S)
Prevention of Transmission of Diseases by Maintaining
Sanitation and Hygiene
Hygiene
Sanitation
Healthy person Faecal matter
2020-21
SCIENCE 178
So, we can be in poor health without there
being a simple cause in the form of an
identifiable disease. This is the reason why,
when we think about health, we think about
societies and communities. On the other
hand, when we think about disease, we think
about individual sufferers.
uestions
1. State any two conditions essential
for good health.
2. State any two conditions essential
for being free of disease.
3. Are the answers to the above
questions necessarily the same or
different? Why?
13.2 Disease and Its Causes
13.2.1 WHAT DOES DISEASE LOOK LIKE?
Let us now think a little more about
diseases. In the first place, how do we know
that there is a disease? In other words, how
do we know that there is something wrong
with the body? There are many tissues in
the body, as we have seen in Chapter 6.
These tissues make up physiological
systems or organ systems that carry out
body functions. Each of the organ systems
has specific organs as its parts, and it has
particular functions. So, the digestive
system has the stomach and intestines, and
it helps to digest food taken in from outside
the body. The musculoskeletal system,
which is made up of bones and muscles,
holds the body parts together and helps the
body move.
When there is a disease, either the
functioning of one or more systems of the body
will change for the worse. These changes give
rise to symptoms and signs of disease.
Symptoms of disease are the things we feel as
being ‘wrong’. So we have a headache, we have
cough, we have loose motions, we have a
wound with pus; these are all symptoms.
These indicate that there may be a disease, but
they don’t indicate what the disease is. For
example, a headache may mean just
examination stress or, very rarely, it may
mean meningitis, or any one of a dozen
different diseases.
Signs of disease are what physicians will
look for on the basis of the symptoms. Signs
will give a little more definite indication of the
presence of a particular disease. Physicians will
also get laboratory tests done to pinpoint the
disease further.
13.2.2 ACUTE AND CHRONIC DISEASES
The manifestations of disease will be different
depending on a number of factors. Some
diseases last for only very short periods of time,
and these are called acute diseases. We all know
from experience that the common cold lasts
only a few days. Other ailments can last for a
long time, even as much as a lifetime, and are
called chronic diseases. An example is the
infection causing elephantiasis, which is very
common in some parts of India.
Activity _____________13.4
• Survey your neighbourhood to find out:
(1) how many people suffered from
acute diseases during the last
three months,
(2) how many people developed
chronic diseases during this same
period,
(3) and finally, the total number of
people suffering from chronic
diseases in your neighbourhood.
• Are the answers to questions (1) and
(2) different?
• Are the answers to questions (2) and
(3) different?
• What do you think could be the
reason for these differences? What do
you think would be the effect of these
differences on the general health of
the population?
13.2.3CHRONIC DISEASES AND POOR
HEALTH
Acute and chronic diseases have different
effects on our health. Any disease that causes
poor functioning of some part of the body will
affect our health. This is because all functions
of the body are necessary for being healthy.
Q
2020-21
WHY DO WE FALL ILL? 179
difference or the poor nourishment alone
would not lead to loose motions. But they do
become contributory causes of the disease.
Why was there no clean drinking water for
the baby? Perhaps because the public services
are poor where the baby’s family lives. So,
poverty or lack of public services become third
cause of the baby’s disease.
It will now be obvious that all diseases will
have immediate causes and contributory
causes. Also, most diseases will have many
causes, rather than one single cause.
13.2.5 INFECTIOUS AND NON-INFECTIOUS
CAUSES
As we have seen, it is important to keep public
health and community health factors in mind
when we think about causes of diseases. We
can take that approach a little further. It is
useful to think of the immediate causes of
disease as belonging to two distinct types. One
group of causes is the infectious agents,
mostly microbes or micro-organisms.
Diseases where microbes are the immediate
causes are called infectious diseases. This is
because the microbes can spread in the
community, and the diseases they cause will
spread with them.
Things to ponder
1. Do all diseases spread to people
coming in contact with a sick person?
2. What are the diseases that are not
spreading?
3. How would a person develop those
diseases that don’t spread by contact
with a sick person?
On the other hand, there are also diseases
that are not caused by infectious agents. Their
causes vary, but they are not external causes
like microbes that can spread in the
community. Instead, these are mostly internal,
non-infectious causes.
For example, some cancers are caused by
genetic abnormalities. High blood pressure
can be caused by excessive weight and lack
of exercise. You can think of many other
diseases where the immediate causes will not
be infectious.
But an acute disease, which is over very soon,
will not have time to cause major effects on
general health, while a chronic disease will do
so.
As an example, think about a cough and
cold, which all of us have from time to time.
Most of us get better and become well within a
week or so. And there are no lasting effects on
our health. But if we get infected with a chronic
disease such as tuberculosis of the lungs, then
being ill over the years does make us lose
weight and feel tired all the time.
We may not go to school for a few days if
we have an acute disease. But a chronic
disease will make it difficult for us to follow
what is being taught in school and reduce our
ability to learn. In other words, we are likely
to have prolonged general poor health if we
have a chronic disease. Chronic diseases
therefore, have very drastic long-term effects
on people’s health as compared to acute
diseases.
13.2.4CAUSES OF DISEASES
What causes disease? When we think about
causes of diseases, we must remember that
there are many levels of such causes. Let us
look at an example. If there is a baby suffering
from loose motions, we can say that the cause
of the loose motions is probably an infection.
But the next question is – where did the
infection come from? Suppose we find that the
infection came through unclean drinking
water. But many babies must have had this
unclean drinking water. So, why is it that one
baby developed loose motions when the other
babies did not?
One reason might be that this baby is not
healthy. As a result, it might be more likely to
have disease when exposed to risk, whereas
healthier babies would not. Why is the baby
not healthy? Perhaps because it is not well
nourished and does not get enough food. So,
lack of good nourishment becomes a second
cause of the disease. Further, why is the baby
not well nourished? Perhaps because it is from
a household which is poor.
It is also possible that the baby has some
genetic difference that makes it more likely to
suffer from loose motions when exposed to a
pathogen. Without the pathogen, the genetic
2020-21
Page 5


Activity _____________13.1
• We have all heard of the earthquakes in
Latur, Bhuj, Kashmir etc. or the cyclones
that lashed the coastal regions. Think
of as many different ways as possible in
which people’s health would be affected
by such a disaster if it took place in our
neighbourhood.
• How many of these ways we can think of
are events that would occur when the
disaster is actually happening?
• How many of these health-related events
would happen long after the actual
disaster, but would still be because of the
disaster?
• Why would one effect on health fall into
the first group, and why would another
fall into the second group?
When we do this exercise, we realise that
health and disease in human communities
are very complex issues, with many
interconnected causes. We also realise that
the ideas of what ‘health’ and ‘disease’ mean
are themselves very complicated. When we
ask what causes diseases and how we prevent
them, we have to begin by asking what these
notions mean.
We have seen that cells are the basic units
of organisms. Cells are made of a variety of
chemical substances–proteins, carbo-hydrates,
fats or lipids, and so on. Cell is a dynamic place.
Something or the other is always happening
inside them. Complex reactions and repair goes
on inside cells. New cells are being made. In
our organs or tissues, there are various
specialised activities going on– the heart is
beating, the lungs are breathing, the kidney
is filtering urine, the brain is thinking.
All these activities are interconnected. For
example, if the kidneys are not filtering urine,
poisonous substances will accumulate. Under
such conditions, the brain will not be able to
think properly. For all these interconnected
activities, energy and raw material are needed.
Food is a necessity for cell and tissue functions.
Anything that prevents proper functioning of
cells and tissues will lead to a lack of proper
activity of the body.
It is in this context that we will look at the
notions of health and disease.
13.1 Health and its Failure
13.1.1 THE SIGNIFICANCE OF ‘HEALTH’
We have heard the word ‘health’ used quite
frequently. We use it ourselves as well, when
we say things like ‘my grandmother’s health
is not good’. Our teachers use it when they
scold us saying ‘this is not a healthy attitude’.
What does the word ‘health’ mean?
If we think about it, we realise that it
always implies the idea of ‘being well’. We can
think of this well-being as effective
functioning. For our grandmothers, being able
to go out to the market or to visit neighbours
is ‘being well’, and not being able to do such
things is ‘poor health’. Being interested in
following the teaching in the classroom so that
we can understand the world is called a
‘healthy attitude’; while not being interested
is called the opposite. ‘Health’ is therefore a
state of being well enough to function well
physically, mentally and socially.
13.1.2 PERSONAL AND COMMUNITY ISSUES
BOTH MATTER FOR HEALTH
If health means a state of physical, mental and
social well-being, it cannot be something that
13
W W W W WHY HY HY HY HY D D D D DO O O O O W W W W WE E E E E F F F F FALL ALL ALL ALL ALL I I I I ILL LL LL LL LL? ? ? ? ?
Chapter
2020-21
healthy. Social equality and harmony are
therefore necessary for individual health. We
can think of many other such examples of
connections between community issues and
individual health.
each one of us can achieve entirely on our own.
The health of all organisms will depend on
their surroundings or their environment. The
environment includes the physical
environment. So, for example, health is at risk
in a cyclone in many ways.
Human beings live in societies. Our social
environment, therefore, is an important factor
in our individual health. We live in villages,
towns or cities. In such places, even our
physical environment is decided by our social
environment.
Consider what would happen if no agency
is ensuring that garbage is collected and
disposed. What would happen if no one takes
responsibility for clearing the drains and
ensuring that water does not collect in the
streets or open spaces?
So, if there is a great deal of garbage
thrown in our streets, or if there is open drain-
water lying stagnant around where we live,
the possibility of poor health increases.
Therefore, public cleanliness is important for
individual health.
Activity _____________13.2
• Find out what provisions are made by
your local authority (panchayat/
municipal corporation) for the supply
of clean drinking water.
• Are all the people in your locality able
to access this?
Activity _____________13.3
• Find out how your local authority
manages the solid waste generated in
your neighbourhood.
• Are these measures adequate?
• If not, what improvements would you
suggest?
• What could your family do to reduce
the amount of solid waste generated
during a day/week?
We need food to be healthy, and this food
will have to be earned by doing work. For this,
the opportunity to do work has to be available.
We need to be happy in order to be truly
healthy, and if we mistreat each other and are
afraid of each other, we cannot be happy or
WHY DO WE FALL ILL? 177
13.1.3 DISTINCTIONS BETWEEN ‘HEALTHY’
AND ‘DISEASE-FREE’
If this is what we mean by ‘health’, what do we
mean by ‘disease’? The word is actually self-
explanatory – we can think of it as ‘disease’ –
disturbed ease. Disease, in other words,
literally means being uncomfortable. However,
the word is used in a more limited meaning.
We talk of disease when we can find a specific
and particular cause for discomfort. This does
not mean that we have to know the absolute
final cause;  we can say that someone is
suffering from diarrhoea without knowing
exactly what has caused the loose motions.
We can now easily see that it is possible to
be in poor health without actually suffering
from a particular disease. Simply not being
diseased is not the same as being healthy.
‘Good health’ for a dancer may mean being
able to stretch his body into difficult but
graceful positions. On the other hand, good
health for a musician may mean having enough
breathing capacity in his/her lungs to control
the notes from his/her flute. To have the
opportunity to realise the unique potential in
all of us is also necessary for real health.
The Five ‘F’s — What is to be done?
Protect the water source (H)
Treat and store water
safely (S)
Wash hands before preparing and
taking food (H)
Wash hands after defecation (S)
Cover the food (H)
Control flies (S)
Clean vegetables and fruits before
use (H)
Avoid open defecation (S)
Proper drainage system (H)
Treatment of water (S)
Prevention of Transmission of Diseases by Maintaining
Sanitation and Hygiene
Hygiene
Sanitation
Healthy person Faecal matter
2020-21
SCIENCE 178
So, we can be in poor health without there
being a simple cause in the form of an
identifiable disease. This is the reason why,
when we think about health, we think about
societies and communities. On the other
hand, when we think about disease, we think
about individual sufferers.
uestions
1. State any two conditions essential
for good health.
2. State any two conditions essential
for being free of disease.
3. Are the answers to the above
questions necessarily the same or
different? Why?
13.2 Disease and Its Causes
13.2.1 WHAT DOES DISEASE LOOK LIKE?
Let us now think a little more about
diseases. In the first place, how do we know
that there is a disease? In other words, how
do we know that there is something wrong
with the body? There are many tissues in
the body, as we have seen in Chapter 6.
These tissues make up physiological
systems or organ systems that carry out
body functions. Each of the organ systems
has specific organs as its parts, and it has
particular functions. So, the digestive
system has the stomach and intestines, and
it helps to digest food taken in from outside
the body. The musculoskeletal system,
which is made up of bones and muscles,
holds the body parts together and helps the
body move.
When there is a disease, either the
functioning of one or more systems of the body
will change for the worse. These changes give
rise to symptoms and signs of disease.
Symptoms of disease are the things we feel as
being ‘wrong’. So we have a headache, we have
cough, we have loose motions, we have a
wound with pus; these are all symptoms.
These indicate that there may be a disease, but
they don’t indicate what the disease is. For
example, a headache may mean just
examination stress or, very rarely, it may
mean meningitis, or any one of a dozen
different diseases.
Signs of disease are what physicians will
look for on the basis of the symptoms. Signs
will give a little more definite indication of the
presence of a particular disease. Physicians will
also get laboratory tests done to pinpoint the
disease further.
13.2.2 ACUTE AND CHRONIC DISEASES
The manifestations of disease will be different
depending on a number of factors. Some
diseases last for only very short periods of time,
and these are called acute diseases. We all know
from experience that the common cold lasts
only a few days. Other ailments can last for a
long time, even as much as a lifetime, and are
called chronic diseases. An example is the
infection causing elephantiasis, which is very
common in some parts of India.
Activity _____________13.4
• Survey your neighbourhood to find out:
(1) how many people suffered from
acute diseases during the last
three months,
(2) how many people developed
chronic diseases during this same
period,
(3) and finally, the total number of
people suffering from chronic
diseases in your neighbourhood.
• Are the answers to questions (1) and
(2) different?
• Are the answers to questions (2) and
(3) different?
• What do you think could be the
reason for these differences? What do
you think would be the effect of these
differences on the general health of
the population?
13.2.3CHRONIC DISEASES AND POOR
HEALTH
Acute and chronic diseases have different
effects on our health. Any disease that causes
poor functioning of some part of the body will
affect our health. This is because all functions
of the body are necessary for being healthy.
Q
2020-21
WHY DO WE FALL ILL? 179
difference or the poor nourishment alone
would not lead to loose motions. But they do
become contributory causes of the disease.
Why was there no clean drinking water for
the baby? Perhaps because the public services
are poor where the baby’s family lives. So,
poverty or lack of public services become third
cause of the baby’s disease.
It will now be obvious that all diseases will
have immediate causes and contributory
causes. Also, most diseases will have many
causes, rather than one single cause.
13.2.5 INFECTIOUS AND NON-INFECTIOUS
CAUSES
As we have seen, it is important to keep public
health and community health factors in mind
when we think about causes of diseases. We
can take that approach a little further. It is
useful to think of the immediate causes of
disease as belonging to two distinct types. One
group of causes is the infectious agents,
mostly microbes or micro-organisms.
Diseases where microbes are the immediate
causes are called infectious diseases. This is
because the microbes can spread in the
community, and the diseases they cause will
spread with them.
Things to ponder
1. Do all diseases spread to people
coming in contact with a sick person?
2. What are the diseases that are not
spreading?
3. How would a person develop those
diseases that don’t spread by contact
with a sick person?
On the other hand, there are also diseases
that are not caused by infectious agents. Their
causes vary, but they are not external causes
like microbes that can spread in the
community. Instead, these are mostly internal,
non-infectious causes.
For example, some cancers are caused by
genetic abnormalities. High blood pressure
can be caused by excessive weight and lack
of exercise. You can think of many other
diseases where the immediate causes will not
be infectious.
But an acute disease, which is over very soon,
will not have time to cause major effects on
general health, while a chronic disease will do
so.
As an example, think about a cough and
cold, which all of us have from time to time.
Most of us get better and become well within a
week or so. And there are no lasting effects on
our health. But if we get infected with a chronic
disease such as tuberculosis of the lungs, then
being ill over the years does make us lose
weight and feel tired all the time.
We may not go to school for a few days if
we have an acute disease. But a chronic
disease will make it difficult for us to follow
what is being taught in school and reduce our
ability to learn. In other words, we are likely
to have prolonged general poor health if we
have a chronic disease. Chronic diseases
therefore, have very drastic long-term effects
on people’s health as compared to acute
diseases.
13.2.4CAUSES OF DISEASES
What causes disease? When we think about
causes of diseases, we must remember that
there are many levels of such causes. Let us
look at an example. If there is a baby suffering
from loose motions, we can say that the cause
of the loose motions is probably an infection.
But the next question is – where did the
infection come from? Suppose we find that the
infection came through unclean drinking
water. But many babies must have had this
unclean drinking water. So, why is it that one
baby developed loose motions when the other
babies did not?
One reason might be that this baby is not
healthy. As a result, it might be more likely to
have disease when exposed to risk, whereas
healthier babies would not. Why is the baby
not healthy? Perhaps because it is not well
nourished and does not get enough food. So,
lack of good nourishment becomes a second
cause of the disease. Further, why is the baby
not well nourished? Perhaps because it is from
a household which is poor.
It is also possible that the baby has some
genetic difference that makes it more likely to
suffer from loose motions when exposed to a
pathogen. Without the pathogen, the genetic
2020-21
SCIENCE 180
The ways in which diseases spread, and
the ways in which they can be treated and
prevented at the community level would be
different for different diseases. This would
depend a lot on whether the immediate causes
are infectious or non-infectious.
uestions
1. List any three reasons why you
would think that you are sick and
ought to see a doctor. If only one
of these symptoms were present,
would you still go to the doctor?
Why or why not?
2. In which of the following case do
you think the long-term effects on
your health are likely to be most
unpleasant?
• if you get jaundice,
• if you get lice,
• if you get acne.
Why?
13.3 Infectious Diseases
13.3.1INFECTIOUS AGENTS
We have seen that the entire diversity seen in
the living world can be classified into a few
groups. This classification is based on
common characteristics between different
organisms. Organisms that can cause disease
are found in a wide range of such categories
of classification. Some of them are viruses,
some are bacteria, some are fungi, some are
single-celled animals or protozoans (Fig. 13.1).
Some diseases are also caused by
multicellular organisms, such as worms of
different kinds.
Peptic ulcers and the Nobel prize
For many years, everybody used to think
that peptic ulcers, which cause acidity–
related pain and bleeding in the stomach
and duodenum, were because of lifestyle
reasons. Everybody thought that a stressful
life led to a lot of acid secretion in the
stomach, and eventually caused peptic
ulcers.
Then two Australians made a discovery
that a bacterium, Helicobacter pylori, was
responsible for peptic ulcers. Robin Warren
(born 1937), a pathologist from Perth,
Australia, saw these small curved bacteria
in the lower part of the stomach in many
patients. He noticed that signs of
inflammation were always present around
these bacteria. Barry Marshall (born 1951),
a young clinical fellow, became interested
in Warren’s findings and succeeded in
cultivating the bacteria from these sources.
In treatment studies, Marshall and
Warren showed that patients could be cured
of peptic ulcer only when the bacteria were
killed off from the stomach. Thanks to this
pioneering discovery by Marshall and
Warren, peptic ulcer disease is no longer a
chronic, frequently disabling condition, but
a disease that can be cured by a short
period of treatment with antibiotics.
For this achievement, Marshall and
Q
Warren (seen in the picture) received the
Nobel prize for physiology and medicine in
2005.
2020-21
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