Page 66 - Science Class 07
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from the lungs (expira on). The flow rate of air INTERNAL RESPIRATION
is in propor on to the magnitude of the In the process of internal respira on food
pressure difference.
(glucose) is broken down into simpler
Inhala on : When we inhale air the rib muscle substances and energy is produced. During the
contract and the front ends of the ribs move process of inhala on, air reaches the lungs.
upward and outward. At the same me, the Here, oxygen from the air is diffused in the
diaphragm moves downwards. In this way, a blood and combines with haemoglobin to form
passage is created. oxyhaemoglobin. On reaching the ssue
capillaries, oxyhaemoglobin dissociates to
release oxygen. This oxygen released in the
Aim : To know how rate of breathing ssues is then u lised in breakdown of food,
increases with the increase in physical releasing energy and waste product carbon
ac vi es. dioxide and water. The carbon dioxide formed
Method : Count the number of breathing in enters the blood from the ssues. It is carried
one minute while you are in a relaxed mainly as bicarbonates and partly as carbamide
posi on. Now, run in the field for five haemoglobin (formed by combina on of CO
2
minutes. Again, count the number of with deoxyhaemoglobin). On reaching the
breathing. You will find that the number of lungs, oxygena on of blood causes release of
breathing has increased. Why the number of carbon dioxide from both bicarbonate and
breathing increases with the increase in carbamide haemoglobin. Carbon dioxide is
physical ac vi es? When you run, your body released from the lungs into the atmosphere
needs more energy. As you know, energy is during exhala on. The approximate percentage
released in our body when oxygen breaks of gases is inhaled air and exhaled air for
down food taken. So, to obtain more energy, humans beings are :
more oxygen is required. To meet the Exhaled
required amount of oxygen, we start Gas Inhaled air in % air in %
breathing rapidly when we do more physical Oxygen 21 16
work rapidly for air inside the chest cavity Carbon 0.4 4
and the air from the surroundings enters the
lungs. The lungs get filled with air and hence Water vapour varies 1
the first phase of breathing which in Nitroge 79 79
inhala on is completed.
Composi on of Air While Inhala on and
Exhala on
Exhala on : During exhala on, ribs move
downwards and inwards and at the same me, The above men oned table shows that
the diaphragm moves upwards. In this way, percentage of three important gases like
high pressure area is created and air is forced oxygen, carbon dioxide and nitrogen and trace
to move out of the chest cavity. At this me, of water vapour, during inhala on and
the size of the lungs is reduced as it contracts. exhala on. During normal breathing, an adult
man take in 0.5 litre of air, but on forced
66 Science-7
