Events/ Steps in Respiration
There
are no strict demarcations of events involved in the process of respiration. It
is a very complex process of several biochemical and physical processes. But
for a general understanding on what goes on, we shall study under the following
heads.
Pathway of air:
Let us observe the pathway of air from
nostril to alveolus.
Nostrils: Air usually enters the body through
the nostrils
Nasal cavity: Air is filtered. The moist surface of
the lining of the nasal cavity, and the hairs growing from its sides, remove
some of the tiny particles of dirt in the air. In addition, as the inhaled air
passes through the nasal cavity, its temperature is brought close to that of
the body, and it takes up water vapour so that it becomes more moist than
before.
Pharynx: Warming and moistening goes on in this
common passage of digestive and respiratory system. Epiglottis, a flap like
muscular valve controls movement of food arid air towards their respective
passages.
Larynx: This stiff box contains our vocal
cords. When air passes out of the lungs and over the vocal cords, it causes
them to vibrate. This produces sounds on the basis of our speech, song etc.
Trachea: Wind pipe channeling air to lungs.
Touch your throat to feel the tube like structure.
Bronchus: At its lower end the trachea or the
wind pipe divides into two bronchi-one leading to each lung.
Bronchiloes:
Each bronchi is further divided into smaller and smaller branches called
bronchioles.
Alveolus: These finally terminate in clusters of
air sacs called alveoli in the lungs which are very small and numerous. Gaseous
exchange takes place here as blood capillaries take up oxygen and expel carbon
dioxide.
Blood: Carries oxygen, to each and every cell
of the body and collects CO2 from them.
Mechanism of respiration in human beings:
We know that breathing is the process of inhaling and exhaling. The organs involved are mainly the lungs. You can’t see your lungs, but it’s easy to feel them in action. Put your hands on your chest and breathe in very deeply. You will feel your chest getting slightly bigger. Now breathe out the air, and feel your chest return to its regular size. You’ve just felt the power of your lungs! The lungs themselves can neither draw in air nor push it out. Instead, the chest wall muscles and another flexible flattened muscle called diaphragm helps the lungs in moving air into and
out
of them.
The
chest wall is made up of ribs, muscles, and the skin. The ribs are Attached at
an angle to the spine (if you run your finger along one of your ribs, you will
notice that It extends downward from the spine). When we inhale, the chest wall
moves up and expands. This causes an increase in the volume of the chest
cavity.
The
chest wall is made up of ribs, muscles, and the skin. The ribs are attached at
an angle to the spine (if you run your finger along one of your ribs, you will
notice that it extends downward from the spine). When we inhale, the chest wall
moves up and expands. This causes an increase in the volume of the chest
cavity.
The
diaphragm may be imagined as the ‘floor’ if you think of the chest cavity as a
“room.” When the diaphragm is relaxed when we breath out, it is in the shape of
a dome with the convex side of the dome extending into the chest cavity. When
the diaphragm contracts during inhalation it flattens out a bit or the dome
moves downward. As a result, the volume of the chest cavity is increased.
When
the diaphragm flattens and the volume of the chest cavity is increased, its
internal pressure decreases and the air from the outside rushes into the lungs.
This is inspiration (inhalation).
Then
the reverse occurs. The chest wall is lowered and moves inward, and the
diaphragm relaxes and assumes its dome shape. These changes increase the
pressure on the lungs; their elastic tissue contracts and squeezes the air out
through the nose to the external atmosphere. This is expiration (exhalation).
Gas
|
% in inhaled air
|
% in exhaled air
|
Oxygen
|
21
|
16
|
Carbon dioxide
|
0.03
|
4.4
|
Nitrogen
|
78
|
78
|
Transportation of gases:
When
oxygen present in the air is within normal limits (around 21%) then almost all
of it is carried in the blood by binding to haemoglobin, a protein (quite like
chlorophyll, the only major difference being it has iron in place of magnesium
as in chlorophyll) present in the red blood cells. As oxygen is diffused in the
blood, it rapidly combines with the haemoglobin to form oxyhaemoglobin. Not
only haemoglobin can combine with oxygen, but the reverse can also happen to
yield a molecule of haemoglobin and oxygen.
Carbon
dioxide is usually transported as bicarbonate, while some amount of it combines
with haemoglobin and rest is dissolved in blood plasma. Study the following
equation for better understanding.
Hb+O2 -------------àHbO2(in
lungs)
HbO2 ---------------------àHb+ O 2(in
tissues)
Cellular respiration:
The
term cellular respiration refers to the pathway by which cells release energy
from the chemical bonds of food molecules that enter them. It provides that
energy for the essential processes of life. So living cells must carry out
cellular respiration. It Can be in the presence of oxygen that is ‘aerobic
respiration’ or in its absence that is ‘anaerobic respiration (fermentation)’.
Cellular respiration in prokaryotic cells like that of bacteria occurs within
the cytoplasm. In eukaryotic cells cytoplasm and mitochondria are the sites of
the reactions. The produced energy is stored in mitochondria in the form of
ATP. That is why mitochondria are called “power houses of cell”.
The
exact chemical details of the breakdown of sugar or other foods within a living
cell does not take place as a single reaction, but occurs in a series of small
steps.
How
does this affect the energy release? As the change in the chemical nature of
the molecule from one stage to the next is slight, in any step small amount of
energy is released. The complete breakdown of a sugar molecule with the release
of all its available energy involves a series of different chemical reactions.
From
the breakdown of glucose the energy is released and stored up in a special
compound, known as ATP (adenosine triphosphate). It is a small parcel of
chemical energy. The energy currency of these cells is ATP an energy rich
compound that is capable of supplying energy wherever needed within the cell.
Each
ATP
molecule gives 7200 calories of energy. This energy is stored in the form of
phosphate bonds. If the bond is broken the stored energy is released.
•
Do cells of alveoli or lungs also require oxygen to carry out cellular
respiration? Why/Why not?
In
short, at cellular level we could have the following pathways starting with
glucose (It is one example, remember that there are other components of food as
well).
· By
“respiratory System” we usually mean the passages that transport air to the
lungs and to the microscopic air sacs in them, called alveoli (where gases are
exchanged) and vice versa.
· The term
‘respiration’ refers to the whole chain of processes from the inhalation of air
to the use of oxygen in the cells.
·
Lavoisier
found that the air that we breathe out precipitated lime water
·
Air
passes from nostrils to nasal cavity to pharynx, larynx, trachea, and bronchi,
bronchioles to alveoli and blood and back through the same route.
· Gas
exchange in the lungs takes place in the tiny air sacs called alveoli in the
lungs. The lungs have millions of alveoli and each lies in contact with
capillaries.
· Diaphragm
is a muscular tissue present at the floor of the chest cavity.
·
During
inspiration (inhalation) the volume of the chest cavity is increased as the
diaphragm contracts and dome flattens out, its internal pressure decreases and
the air from the outside rushes into the lungs.
·
During
expiration, the chest wall is lowered and moves inward, and the diaphragm
relaxes and assumes its dome shape. These changes increase the pressure on the
lungs; their elastic tissue Contracts and squeezes the air out through the nose
to the external atmosphere.
·
Air is
filtered in the nasal cavity and the whole length of the trachea.
· The moist
surface of the lining of the nasal cavity, and the hairs growing from its
sides, remove son of the tiny particles of dirt in the air. In addition, as the
inhaled air passes through the nasal cavity, it temperature is brought close to
that of the body, and it takes up water vapour. So that it becomes more moist
than before.
· Pharynx
is a common passage of digestive and respiratory system. Epiglottis, a flap
like muscular valve controls movement of air and food towards their respective
passages.
· Larynx is
a stiff box like structure containing our vocal cords. When air passes out of
the lungs and over the vocal cords, it causes them to vibrate. This produces
sounds on the basis of our speech, song etc.
·
Trachea
is the wind pipe channeling air to lungs.
· At its
lower end the trachea or the wind pipe divides into two bronchi-one leading to
each lung.
· The
bronchi divide into smaller and smaller branches called bronchioles.
· These
finally terminate in clusters of air sacs called alveolus in the lungs which
are very small and numerous. Gaseous exchange takes place here as blood
capillaries take up oxygen and expel carbon dioxide here.
· Aerobic
respiration occurs in adequate supply of air producing a lot of energy, carbon
dioxide and water.
·
Anaerobic
respiration and fermentation occurs in inadequate supply or absence of oxygen
to produce energy.
· Cells may
resort to the breakdown of 3 carbon compound, pyruvate, aerobically or
anaerobically depending upon the availability of oxygen. Usually in
multicellular organisms cells fail to carry am the process of anaerobic respiration
for long.
·
Respiration
is not essentially a process of combustion differ due to following reasons
Glucose must be burnt at high
temperature in the laboratory to liberate energy, if it happened in our cells,
all cells would be burnt.
Once glucose starts burning we can’t
stop the process easily, but living cells are able to exercise control over the
sort of burning of glucose in the presence of oxygen.
Water normally stops combustion from
taking place while cells contain a lot of water and respiration still goes on.
· Photosynthesis
and respiration appear to be opposing reactions, but both have very different
biochemical pathways and are essential for a plant’s metabolism,
· Photosynthesis
takes place in the chloroplast to produce sugars, starches and other
carbohydrates for the plant’s metabolic needs.
· Cellular
respiration occurs in mitochondria where mainly these carbohydrates are
“burned” to produce chemical energy to do work at the cellular level.
The
Indian ayurvedic physician. Patanjali developed a scientific breathing practice
called Yogabhyasa. Maharshi Patanjali proposed a theory called Astanga yoga. He
was introduced 195 yogic principles in, eight divisions.
1.
Yania (Social disipline),
2.
Niyama (Individual disipline),
3.
Asana (Body posture),
4.
Pranayama (Expansion of vital energy),
5. Prathyahara (With drawal of senses),
6. Dharana (Concentration),
7.
Dhya.na (Meditation),
8. Samadi (Self realisation).