BIOLOGY FORM 4 CHAPTER 7 - RESPIRATION PART 1

1. BIOLOGY FORM 4
CHAPTER 7
RESPIRATION PART 1

2. Objectives
7.1 Understanding the respiratory processes in energy
production
7.2 Analysing the respiratory structure and breathing
mechanism in human and animal
7.3 Understanding the concept of gaseous exchange
across the respiratory surfaces and transport of
gases in human
7.4 Understanding the regulatory mechanism in
respiration
7.5 Realising the importance of maintaining a healthy
respiratory system
7.6 Understanding respiration in plants

3. 7.1
Understanding the respiratory
processes in energy production

4. The respiratory gases
• are:

5. cells need to:
obtain O2
WHY?
eliminate CO2
WHY?

6. cells need to:
obtain O2 to
produce ATP
eliminate CO2
to prevent
toxic effects

7. What is respiration??
Process of obtaining oxygen
and delivering it to the cells
for cellular respiration
and
removing carbon dioxide
produced by cells

8. Respiration
External Respiration
(Breathing)
Internal Respiration
(Cellular respiration)
Aerobic
Respiration
Anaerobic
Respiration
2 stages
2 types

9. External respiration
(Breathing)
• The exchange of respiratory gases (oxygen
and carbon dioxide) between the body and
the environment

10. Internal respiration
( Cellular Respiration)
• A metabolic process
• which occurs in cells,
• involves oxidation of organic molecules(food)
• to produce energy (in the form of ATP)
• Controlled by enzymes
Two types :
1. Aerobic respiration
2. Anaerobic respiration

12. The main substrate to
produce energy is
GLUCOSE

13. Fuels are used in sequence
Muscle
Glucose is stored here
as glycogen and is used
when the body is
working harder.
1. CARBOHYDRATES
2. FATS
3. PROTEINS
Liver
Here some of the
glucose is stored as
glycogen and used to
maintain blood sugar
levels.
Used when the
carbohydrates are
exhausted. Are
first converted to
glycerol and fatty
acids
Used when
carbohydrates
and fats have
been used up as
during prolonged
starvation

15. ENERGY

16. How does body convert
energy stored in food
 energy for body use?

17. Through Cellular
Respiration
 Cellular Respiration is the oxidation of food (glucose)
with the release of energy in living cells
2 Types of Cellular Respiration:
Aerobic and Anaerobic respiration

18. Aerobic respiration
• Require oxygen
• Glucose is completely oxidised
• to produce 36 - 38 molecules of ATP
/ 2898 kJ energy (high energy)
• Takes place in the cytoplasm and mitochondria
C6H12O6 + 6O2
6CO2 + 6H2O + Energy (2898 kJ)

19. Anaerobic respiration
• Without oxygen
• Glucose is not completely broken down
• Releases only 2 ATP (low energy)
• Takes place in the cytoplasm
• Eg. In human muscles, yeast, microbes in
mud
Yeast:
Glucose  Carbon dioxide + ethanol + 210 kJ energy
Muscle:
Glucose  Lactic acid + 150 kJ energy

20. Some microbes living in the mud… low oxygen
level …
Respire ananerobically!

21. • Respiration without oxygen.

22. YYeEaAsSTt!

23. Anaerobic respiration in yeast
•Yeast normally respires aerobically
•Anaerobic respiration in yeast produces
ethanol, carbon dioxide and energy

24. IN YEAST
• Anaerobic respiration in yeast also
known as fermentation
C6H12O6
2CO2 + 2C2H5OH + Energy(210kJ)
ethanol
Zymase
• Ethanol can be used in wine & beer production
• CO2 released causes the dough to rise (to make bread)

25. Alcoholic Fermentation
C6H12O6
 2C2H5OH + 2CO2 + energy
glucose ethanol carbon
dioxide
• Occurs in yeast cells.

26. Dough rising 36
The yeast is mixed
with the dough
After 1 hour in a warm
place the dough has
risen as a result of the
carbon dioxide
produced by the yeast

27. Anaerobic Respiration
Glucose (with baker’s yeast)
 Carbon dioxide + ethanol + little energy (210kJ)
The ‘holes’ in the
bread are made by
the carbon dioxide
bubbles.
This gives the bread a
‘light’ texture

28. Anaerobic respiration in humans!
Highly intensive exercise
Glucose  Lactic acid + energy

29. Anaerobic Respiration in the Muscles
1. Vigorous muscle movement  increase rate of aerobic
respiration to release more energy.
Glucose + oxygen  Carbon dioxide + water + 2898kJ
energy

30. What happens when you need more
energy but there’s not enough oxygen?

31. Muscle cells (anaerobic respiration)
• Prolonged physical activity
- O2 supplied not enough
- O2 needed > O2 supplied
- muscle cells undergo anaerobic respiration
• Muscles in state of O2 deficiency  O2 debt
occurred
• Oxygen debt : muscle cells produce ATP
without oxygen

32. • Glucose molecules break down partially into
Lactic Acid
C6H12O6 2C3H6O3 + Energy (150kJ)
lactic acid
• Energy low because much of energy still trapped
within molecules of lactic acid.
• High concentration of lactic acid
may cause muscular cramp and
fatigue, tiredness

33. “Repaying” oxygen debt
• After the activity the person need to breathe
deeply and rapidly to inhale more O2
- O2 is used to oxidise accumulated lactic acid
to form CO2 and H2O (occur mainly in liver)
Lactic acid + O2 CO2 + H2O + energy
Remaining lactic acid converted into glycogen and
stored in muscle cells

34. Oxygen Debt
Question: How do sprinters pay back
their oxygen debt at the end of a race?
Answer: Sprinters will continue to breathe more deeply and rapidly for a
number of minutes at the end of their race. This will enable them to pay
back the oxygen debt, and allow lactic acid levels to fall.

35. Oxygen debt
The amount of oxygen needed to remove lactic acid from
muscle cells is called oxygen debt
The time taken to remove all the lactic acid is called the
recovery period

36. • Oxygen debt is paid off when all of
lactic acid is removed (increasing
breathing rate after vigorous activity)

37. Energy needed for vigorous
exercise
Glucose + oxygen  Carbon dioxide + water + 2898 kJ
Glucose + Oxygen  Lactic acid + 150 kJ
Total amount of energy
needed for vigorous muscular
contractions
Aerobic respiration
Anaerobic respiration

38. Why aerobic respiration
produced more energy than
anaerobic respiration???

39. Why are virtually all organisms aerobes?
More ATP
released in
aerobic rather
than in
anaerobic
respiration

40. Aerobic and Anaerobic
Respiration
RESPIRATION
Anaerobic
Respiration
Alcoholic
Fermentation
Lactic Acid
Production
Aerobic
Respiration
C6H12O6 + 6O2
 6CO2 + 6H2O + energy
glucose oxygen carbon water
dioxide
C6H12O6
 2C2H5OH + 2CO2 + energy
glucose ethanol carbon
dioxide
• Occurs in yeast cells.
C6H12O6
 2C3H6O3 + energy
glucose lactic
acid
• Occurs in muscle cells.
• Leads to fatigue.

41.  SIMILARITIES
 Cellular respiration
 Involve the breakdown of glucose
 Produces energy
 Are catalyzed by enzymes
 Occurs in animal and plants

42. Differences between Aerobic Respiration &
Anaerobic Respiration
Aerobic Respiration Items Anaerobic
Respiration
Almost every living
cells
Work in Certain plant, yeast,
bacteria and muscle
Required Oxygen requirement Not required
Complete oxidation Oxidation of glucose Incomplete
oxidation
CO2, Water and
Energy
Product Yeast
CO2, Ethanol and
Energy
Muscle
Lactic acid and
Energy

43. Differences between Aerobic Respiration &
Anaerobic Respiration
Aerobic Respiration Items Anaerobic Respiration
Large amount Energy released Small amount
Mitochondria and
Site Cytoplasm
cytoplasm
C6H12O6 + 6O2
Glucose
↓
6CO2 + H20 + 2898 kJ
Energy
Chemical Equation In Yeast:
C6H12O6
Glucose
↓
2CO2 + 2C2H5OH + 210 kJ
Ethanol Energy
In Muscle cells:
C6H12O6
Glucose
↓
2C3H6O3 + 150kJ
Lactic acid Energy
38 molecules Number of ATP molecules
produced
2 molecules

44. • This apparatus can be used to investigate how small
living organisms respire such as woodlice, maggots or
germinating seeds.
Living organisms
Gauze
Hydrogen carbonate indicator – This will change
colour from red to yellow when the carbon
dioxide level increases due to respiration.

45. The germinating seeds are respiring and therefore releasing heat. The boiled
seeds have been killed and are therefore not respiring anymore.
Cotton wool
Thermometer
Thermal flask

46. 7.2
Analysing the respiratory structure
and
breathing mechanism in human
and animal

47.  LEARNING OUTCOMES:
 State the respiratory structures in
humans and some animals
 Describe the characteristics of
respiratory surfaces in humans and
other organisms
 Describe breathing mechanisms in
human and other organisms
 Compare and contrast the human
respiratory system with other
organisms

48. Gaseous exchange:
is the exchange of oxygen and carbon
dioxide between the environment and the
organism
takes place in all organisms by diffusion

49. A ‘respiratory surface’ is the:
area where gaseous exchange
actually takes place

50. Adaptations of respiratory structures
(General characteristics)
1. Moist – easy for gases to dissolve
before diffuse
2. Thin – allow rapid diffusion of gases
3. Large surface area – efficient gaseous
exchange
4. Covered by a network of blood
capillaries – efficient exchange and
transport of respiratory gases

51. Organisms acquire their oxygen:
direct from the
atmosphere
dissolved
in water
1 2

52. oxygen
Unicellular organisms
carbon dioxide
maximum
distance
is 0.1 mm
The distance is so small that diffusion is rapid
enough for the cell’s needs
Amoeba

53. Protozoa – Unicellular Organism
Oxygen
nutrients
Carbon
dioxide
Waste
products
The respiratory surface of an unicellular
organism is through plasma membrane

54. Adaptations
1. Small Size
 large surface area to volume (TSA/V) ratio
 rate of diffusion increases
2. Wet surroundings
 plasma membrane constantly moist
 gases easily dissolve and diffuse
across respiratory surface.
3. Thin plasma membrane
 rapid diffusion of gases

55. Unicellular Organism
No need for specialized respiratory
structure

56. • Concentration of O2 is higher in
surrounding water compared to the cell,
so O2 diffuse into the cell through
plasma membrane by simple diffusion
EXAM TIPS!!!
• Concentration of CO2 is higher in the cell
compared to the surrounding water, so
CO2 diffuse out of the cell through
plasma membrane by simple diffusion

57. As animals increase in size:
What happens to their surface area to volume
ratio?
Surface area (cm):
Volume (cm3):
Surface area/volume:

58. The larger the size
of organism, the
smaller the TSA/V
ratio

59. As animals increase in size:
What happens to the rate of oxygen
consumption?
INCREASES
What must happen to meet the increased
demand?
Specialised respiratory surfaces
must develop

60. Give TWO reasons for this statement:
Some types of animals exchange gases without
specialised respiratory structures.
1. the size & shape of the body
 body is extremely small &
elongated, as in
microscopic nematode
worms: short diffusion
pathway
 the body may be thin &
flattened, producing a large
surface area for diffusion
(as in flatworms)
Nematode worm
Flatworm

61. 2. if energy demands are low:
 the relatively slow rate of gas
exchange by diffusion may suffice
even for a larger, thicker body e.g. a
jellyfish

62. CO2 diffuses
O out 2 diffuses in
Earthworm
Section through
worm’s skin
0.04mm
the blood vessels
absorb the O2 and
carry it to the body
diffusion takes place through
the thin skin of the worm
16

63. RESPIRATORY STRUCTURE in INSECTS

64. Respiratory structure of Insects
The tracheal system

65. Body
wall
spiracle
tracheole
Body cell
Trachea
(Reinforced with rings of chitin which
prevent from collapsing)
AIR
The tracheal system of an insect
consists of spiracle, trachea, air sac and tracheoles

66. The tracheal system of insects
consists of tiny branching tubes that
penetrate the body

67. Spiracles
 are pairs of holes found on the:
 2nd & 3rd thoracic segments
 first 8 abdominal segments
Air sacs
Spiracle
Tracheae
 lead into air-filled sacs
Spiracles:
Air enters the
tracheae through
spiracles
Spiracles have
valves which allow
air, to go in and out
of the body
Air sacs:
in some larger
insects contain air
that speeds up
movement of gases
during vigorous
body movement.

68. The tracheal system of insects
provides direct exchange between the
air and body cells
Body
cell
Tracheole Air
sac
Trachea
Air Body wall

69. What are ‘tracheae’?
 branched tubes that lead from
spiracles
 reinforced with rings of chitin
which prevent them from collapsing
Why is it important to support the
tracheae?
If trachea collapses, surface
area is greatly reduced

70. Tracheoles:
Numerous
 Tiny, end within cells
 Contains fluid at tip
 Thin - 1 cell thick
Why do tracheoles lack a
chitin lining?
So that the respiratory
surface is very thin
making the diffusion of
oxygen into the cells
easy

71. ADAPTATIONS OF TRACHEOLES
• Large number- provide large surface area for
gases exchange
• Tip of tracheoles have thin permeable wall –
allow rapid diffusion of respiratory gases
• Tips of tracheoles have fluid - allow respiratory
gases to dissolve
• Direct contact with tissues and organs, O2
directly diffuse into the cells, and CO2 directly
diffuse out of the cells (no need blood to
transport)

72. Air enters the spiracle then flows into the:
Tracheae Tracheoles Cells

73. A closer look at a spiracle of a pupa

74. Valves & hairs at a spiracle:
reduce water loss
Valve open Valve closed

75. Ventilation (Breathing) movements
 ventilation is the active movement of air or water
over an animal's respiratory surface
 one-way flow of air through the animal occurs
Air enters in:
through the thorax
Air emerges from
the abdomen
Circulatory system not involved in transporting O2 and CO2

76. VENTILATION IN GRASSHOPPER

77. Breathing Mechanism
Expiration:
 Abdominal muscles contract
& flatten the body
 volume of the tracheal system decrease
 air pressure inside trachea increased
 air is forced out through spiracles
Inspiration:
 Abdominal muscles relax & body
returns to original shape
 Spiracles open
 air pressure inside tracheae
lowered, air drawn in.

78. Compare Ventilation in mammals:
Expiration:
 muscles contract
Inspiration:
 is achieved
passively
Expiration:
 muscles relax
 is achieved passively
Inspiration:
 muscles contract

79. In insects: the circulatory system is not
involved in respiration
blood is colourless (no respiratory
pigment)

80. Question: [Pg. 139]
1) Insects use a tracheal system for gas
exchange, as shown below.
R
a) On the diagram use a line labelled R to
show the respiratory surface. (1)

81. b) State two advantages of using a
tracheal system for gas exchange. (2)
1. Oxygen is transported directly to cells
2. Provides a large surface area for
gaseous exchange

82. Question: [pg. 140]
3) Gas exchange in insects involves pores
in the cuticle which open into a network
of tubes. These tubes have fine branches
extending into all the tissues of the body.
a) Name the following:
The pores in the cuticle. (1)
Spiracles
The network of tubes. (1)
Tracheal system

83. b) In larger insects, such as locusts, the
passage of air through the tubes is helped
by pumping movements of the abdomen. A
student carried out an experiment to
investigate the effect of carbon dioxide on
the rate of these pumping movements. She
set up the apparatus as shown in the
diagram below:

84. The locust was left in the boiling tube for five
minutes. The number of abdominal pumping
movements during one minute was counted. The
student then breathed out once through the
straw into the boiling tube and immediately
counted the number of abdominal movements
during one minute. She repeated this procedure
varying the number of times she breathed out
into the boiling tube. The results are shown in
the table below.

85. Number of times
student breathed
into boiling tube
Number of abdominal
pumping movements in
one minute
0 16
1 59
2 61
3 58
4 60
i) State why the student left the locust in
the boiling tube for five minutes before
she began the first count. (1)
For insect to acclimatise & reach a steady
rate of breathing.

86. Number of times student
breathed into boiling tube
Number of abdominal pumping
movements in one minute
0 16
1 59
2 61
3 58
4 60
ii) Describe and comment on the effect of breathing
out into the boiling tube on the rate of abdominal
pumping in the locust. (4)
A slight increase in CO2 concentration. Resulted in a
high rise in breathing rate.
Addition of more CO2 did not result in a further
increase. Brain is sensitive to slight rise in CO2 .

87. c) (i) During this experiment, the humidity
of the air in the boiling tube may vary.
Suggest how this experiment could be
modified to control the humidity. (2)
Adding silica gel.
+ water = pink

88. (ii) Suggest two factors, other than a
change in carbon dioxide
concentration and humidity, which
may have affected the rate of
abdominal pumping. (2)
An increase in temperature.
Animal becomes stressed.

89. RESPIRATORY STRUCTURE & BREATHING
MECHANISM OF AMPHIBIANS

90. The respiratory structure in an amphibian
Skin
Lung

91. Adaptation of the skin for gases exchange
1.The skin is
thin and
highly
permeable
- To allow rapid
diffusion of
respiratory
gases into
the blood
capillaries
2. Beneath the
skin is a
network of
blood
capillaries
- To transport
respiratory
gases to and
from body
cells
3. The skin is
kept moist by
the secretion
of mucus by
glands found on
the outer
surface of the
body
- Facilitate rapid
and efficient
exchange of
gases between
the skin and
the environment

92. Beneath the skin
is a network of blood capillaries
– to receive O2 and transport it to body cells

93. Adaptation of the Lung for gases exchange
1.The surface
area for
gases
exchange is
increased by
numerous
inner
partition
- To increase
the surface
area for
gases
exchange
2. Covered
with a rich
network of
blood
capillary
- To transport
respiratory
gases to and
from body
cells
3. The
membrane of
the lungs thin
and moist
- Facilitate the
efficient
diffusion of
respiratory
gases in and
out rapidly

94. Floor of the
mouth lower
 During inspiration, the nostrils open, the mouth closes, the glottis closes and the
floor of the mouth cavity is lowered.
 This decrease the air pressure inside the mouth cavity. As the result, air is
drawn thorough the nostrils into the mouth cavity.
 The nostrils close and the floor of the mouth cavity is raised to force the air
through the glottis into the lungs. The lungs expand and gaseous exchange
takes place.
 During expiration, the nostrils open. The muscles of the body wall contracts to
force the air from the lungs to the mouth cavity and nostrils.

95. RESPIRATORY STRUCTURE & BREATHING
MECHANISM OF FISH

96. Respiratory Structure of Fish
The Gill

97. Gill Structure

98. Operculum is a:
 movable gill cover that encloses and
protects the gills

99. Operculum

100. Operculum controls:
 movement of water in and out of the
opercular cavity like a valve

101. Gill:
gill arch + gill filaments
Gill arch
Gill filaments

102. Usually 4 gill arches on either side of the
fish:
 support the gills

104. Gill filaments are thin
Gill filament
Gill raker
[for filter feeding]
Upper limb
Lower limb

105. Each gill is made up of 2 rows of:
gill filaments
(primary
lamellae)
arranged in the
shape of a V
About 70 pairs
of gill filaments

106. The upper & lower flat surfaces of each gill
filament has rows of:
evenly spaced folds
or gill plates
(secondary lamellae)

107. The gill plates (secondary lamellae):
increase the
surface area of the
respiratory surface
have a rich supply
of blood capillaries

108. What makes fish gills look red?
A rich blood supply.

109. The gill plates (secondary lamellae):
are the exchange surfaces
Primary lamellae
or filaments
Plate-like
secondary
lamellae

110. The gill plates (secondary lamellae):
are two-cell thick
Water
Blood flow
flow
Longitudinal section of
secondary lamella
Primary lamellae or
filaments
Plate-like secondary
lamellae

111. Gills are useless out of the water. WHY?
Gill filaments stick together and surface
area is reduced

112. Two types of flow:
Countercurrent flow:
 blood in the gill plates
flows in the opposite
direction to the water (in
bony fish)
Parallel flow [concurrent]:
 when the two fluids
travel in the same
direction (in
cartilaginous fish)

113. Countercurrent Mechanism

114. Explain how a countercurrent flow increases
the efficiency of gaseous exchange.

115. Countercurrent Flow is more efficient:
equlibrium is reached
blood always comes in contact with water
having a high O2 concentration

116. The structural Adaptation of the gills:
a. Thin filament membrane to allow rapid
diffusion of respiratory gases into the
blood capillaries
b. Rich supply of blood capillaries for efficient
exchange and transport of respiratory
gases
c. Surrounded by water – moist -which
enable respiratory gases to be dissolved
d. Large surface area of filaments and
lamellae for efficient gases exchange

117. The Mechanism of Countercurrent Exchange
a. The water flows over the gills in one direction
b. The blood flows in the opposite direction
through blood capillaries in the lamellae
c. As deoxygenated blood enters the blood
capillaries, it encounters water with a higher
oxygen content
d. As the concentration of O2 is higher in water
than in the blood, O2 diffuses into the blood
e. And because the concentration of CO2 in the
blood is higher than in water, CO2 diffuses
from the blood into the water

118. Breathing Mechanism in Fish
EXPIRATION
INSPIRATION

119. Inspiration Expiration

120. • Absorb dissolved oxygen from the
surrounding water
• The membrane of the gill filaments is thin –
allows the absorption of respiratory gases
INHALATION EXHALATION
into the blood capillaries
• The filaments are supplied with blood
capillaries – for efficient exchange and
transport of respiratory gases

121.  During Inhalation, the bony fish
opens its mouth and lowers the
floor of the mouth.
 The pressure inside the mouth
falls below that of the external
pressure. This causes water to
enter the mouth. At the same
time, it causes the operculum to
press against the body.
 Gaseous exchange occurs as
water flows past the grills. Water
then passes out through the
operculum . The operculum
opens due to increased the
pressure in the mouth.

122. RESPIRATORY STRUCTURE AND
BREATHING MECHANISM OF HUMAN

123. RESPIRATORY STRUCTURE IN HUMAN
LUNGS

124. The Human Respiratory System
Nasal cavity
Pharynx
Larynx (‘voice box’)
Trachea (‘windpipe’)
Lungs
Diaphragm
- separates chest
from abdomen

125. Components of the lower respiratory
tract

126. Sequence air passes into human lungs:
2. Pharynx
[throat] 1. nasal passages
4. trachea 3. larynx
lung
5. bronchi
6. bronchioles
7. alveoli

127. What happens as air passes through the nasal
passages?
Cilia
Cell membrane
Mucus

128. Give TWO functions of mucus in the
respiratory system.

129. The wall of the trachea is:
 held open by
horizontally C-shaped
bands of cartilage
 strengthened

131. Each lung is surrounded by a pleural cavity
Pleural cavity:
contains pleural fluid
is air-tight
Pleural fluid:
lubricates space between two layers

132. Drainage from pleural cavity

133. Alveoli

134. alveolus

135. The Human Respiratory System
The wall of each
alveolus is only one cell
thick.
The inner surface is
coated with a thin film
of moisture.
It is supplied by a
capillary whose
wall is also only
one cell thick.
This is the
site where
exchange
of gases
takes place!

136. Alveoli
form the gas exchange surface

137. Alveolar wall – 1 cell thick
consists of very thin, flattened cells:
reducing the distance over which
diffusion must occur
Simple
Squamous
Simple
Cuboidal
Basement membrane
Simple
Columnar

139. Diameter of capillary is smaller
than that of a RBC and so:
RBC move relatively
slowly
 more time for
gaseous exchange
RBC are squeezed
 bend into an umbrella shape – expose
more of their SA to the alveolus:
 more uptake of O2

140. Fig. 11 Gaseous exchange inside an alveolus.

141. 1. Gaseous exchange in humans take place in the lungs
2. Air enters lungs through :
trachea  bronchi  bronchioles  alveoli
3. Trachea is supported by cartilage to prevent it from collapse
during inhalation

142. Large number of alveoli in the
lungs
Walls are made of a single of
cells
Walls secrete a thin lining of
moisture
Surrounded by a network of
blood capillaries
Increased surface area for
gases exchange
Gases can diffuse rapidly
across the thin walls
Gases can dissolve in moisture
and diffuse easily across walls
Can transport oxygen and
CO2 efficiently
• l
ADAPTATION IN ALVEOLUS

143. The mechanism of
ventilation (breathing)

144. A Respiratory Cycle
 Consists of
• An inspiration (inhalation)
• An expiration (exhalation)

145. Gas Pressure and Volume Relationships

146. A change in volume causes pressure to
change

148. The volume of the thoracic cavity changes by:
 movements of the:
 diaphragm  intercostal muscles
TWO types of intercostal muscles
between each rib

149.  slant forwards
& downwards
 contract during
inspiration
 slant backwards &
downwards
 contract during
expiration

150. Fig. 12 Position of intercostal muscles.
The internal intercostal
muscles contract for the
ribcage to return back
The external intercostal
muscles contract to pull the
ribcage up and out

151. Mammals ventilate their lungs by:
 negative pressure breathing, which pulls air into the
lungs
Air inhaled Air exhaled
Lung
INHALATION
Diaphragm contracts
(moves down)
EXHALATION
Diaphragm relaxes
(moves up)
Diaphragm
Rib cage
expands as
external
intercostal
muscles
contract
Rib cage gets
smaller as
external
intercostal
muscles relax
Diaphragm is “dome-shaped Diaphragm flattens out.

152. Inspiration: an active process

153. Expiration: is largely a passive process

154. Inspiration Expiration
Inspiration
 The external intercostals muscles relax while internal intercostals muscles
contract, this raising the ribs upwards and outward.
 At the same time, the diaphragm muscles contract and flatten.
 Both actions above increase the volume of the rib cage, causing its pressure to
decreases.
 Since atmospheric pressure is greater, air is drawn lungs the lungs and they
inflate.

155. Mechanism of Breathing
What happens to your intercostal muscles when you are breathing?
When you inhale, you…
Relax your
Internal intercostal muscles and
Contract your
External intercostal muscles
When you exhale, your…
External intercostal muscles
Relax and your
Internal intercostal muscles
Contract

157. Using a Bell Jar to
demonstrate the
action of Diaphragm

158. rubber sheet
(diaphragm)
What happens to the balloons when the rubber sheet is
pulled downwards ?
The balloons inflate when the rubber sheet is
pulled downwards.
Ans:
glass tube
(trachea)
air space of bell
jar (pleural cavity)
side tube
(bronchus)
wall of bell jar balloon (lung)
(thoracic wall)
handle
balloons are
inflated as rubber
sheet is pulled
downwards
air

159. rubber sheet
(diaphragm)
What happens when the rubber sheet is released ?
The balloons return to their original shape when it
is released.
Ans:
glass tube
(trachea)
air space of bell jar
(pleural cavity)
side tube
(bronchus)
wall of bell jar balloon (lung)
(thoracic wall)
handle
balloons are
inflated as rubber
sheet is pulled
downwards
air

160. rubber sheet
(diaphragm)
When rubber sheet is pulled downwards, volume
inside bell jar increases and pressure decreases. Air is
sucked into the balloons and inflated them. . .
Ans:
glass tube
(trachea)
air space of bell jar
(pleural cavity)
side tube
(bronchus)
wall of bell jar balloon (lung)
(thoracic wall)
handle
balloons are
inflated as rubber
sheet is pulled
downwards
air
Explain how it works.

161. Explain how it works.
rubber sheet
(diaphragm)
When rubber sheet is released, it becomes flattened.
Volume inside bell jar decreases but pressure increases.
Balloons return to original size and force air out.
Ans:
glass tube
(trachea)
air space of bell jar
(pleural cavity)
side tube
(bronchus)
wall of bell jar balloon (lung)
(thoracic wall)
handle
balloons are
inflated as rubber
sheet is pulled
downwards
air

162. glass tube
(trachea)
air space of bell jar
(pleural cavity)
side tube
(bronchus)
air
wall of bell jar balloon (lung)
(thoracic wall)
rubber sheet
(diaphragm)
handle
balloons are
inflated as rubber
sheet is pulled
downwards
Explain why this model does not truly and fully reflect
the actual conditions in man.

163. It is because :
• The rubber sheet is controlled by hand
– the movement of diaphragm is automatic ( contraction brought
about by diaphragm muscles )
• The rubber sheet is flattened at rest
– the diaphragm is dome-shaped

164. • The rubber sheet is pulled downwards to fill the
balloons with air
– the diaphragm is flattened during inspiration
• The wall of the bell-jar is rigid
– rib cage is movable and relatively elastic
• The cavity is filled with air
– the pleural cavity is filled with pleural fluid

165. Using a Rib Cage Model to
demonstrate the action of
Intercostal Muscles

166. Which parts of the human
chest are represented by rod
P, rod Q, rod R and the elastic
band respectively ?
Rod P, rod Q, rod R and
the elastic band
represent the backbone,
sternum, ribs and
intercostal muscles
respectively.
Ans:
A
rod R at
position Y
B
elastic
band
rod Q at position X
rod Q at
position Y
rod R at
position
x
rod P

167. What movement of the
human body is demonstrated
when rods Q and R are raised
from position X to position Y ?
Upward movement of
the chest is
demonstrated when
rods Q and R are raised
from position X to
position Y.
Ans:
A
rod R at
position Y
B
elastic
band
rod Q at position X
rod Q at
position Y
rod R at
position
x
rod P

168. How is the movement in
Question 2 brought about
in the human body ?
It is brought about by
the contraction of
intercostal muscles.
Ans:
A
rod R at
position Y
B
elastic
band
rod Q at position X
rod Q at
position Y
rod R at
position
x
rod P

169. What process occurs in the
human body as a result of
the movement referred to in
Question 2 ?
Ans: Inspiration.
A
rod R at
position Y
B
elastic
band
rod Q at position X
rod Q at
position Y
rod R at
position
x
rod P

170. Describe and explain the
sequence of events
involved in this process
referred in Question 2.
During inspiration the
volume of the thorax is
increased and the
pressure is then
reduced. Air is forced
into the lungs.
Ans:
A
rod R at
position Y
B
elastic
band
rod Q at position X
rod Q at
position Y
rod R at
position
x
rod P

171. BREATHING MECHANISMS IN
HUMAN
INHALATION EXHALATION
External intercostal muscles
contract
External intercostal muscles
relax
Internal intercostal muscles relax Internal intercostal muscles
contract
Rib cage move upwards and
outwards
Rib cage move downwards and
inwards
Diaphragm contracts and flattens Diaphragm relaxes and returns to
dome-shaped
Volume of thoracic cavity increase
resulting in reduced air pressure in
alveoli
Volume of thoracic cavity decrease
resulting in higher air pressure in
alveoli
Higher atmospheric pressure
outside causes air to rush in
Air is forced out of lungs

172. Structures Inhalation Exhalation
External intercostal
muscles
Internal intercostal
muscles
Rib cage
Diaphragm
Volume
Pressure
Air flow

173. 1. Respiratory structures involve in gaseous
exchange:
a) Across plasma membrane
b) Tracheal system - insects
c) Gills - fish
d) Skin
e) Lungs

174. Common characteristics of respiratory structures
• Moist (gaseous dissolving &
diffusion)
• Thin (rapid diffusion)
• Large surface area per
volume
• Network of blood
capillaries beneath the
respiratory surfaces.

175. Compare and contrast the human respiratory
system with that of other organisms

176. Adaptati
on
Organis
ms
Large
surface
area
Respiratory
structure
Moisture Network of
blood
capillaries
Protozoa Small size Plasma
membrane
Dissolved
gases
None
Insects Numerous
tracheoles
Tracheoles Tip of
tracheoles
None
Fish Numerous
filaments
and
lamellae
filaments
and lamellae
Dissolved
gases
Available
Amphibians Lungs
skin
Lungs and
skin
Wet skin Available
Humans Numerous
alveoli Moist
Available

177. Respirometer is used to find:
the RATE of
respiration
measured as:
volume of oxygen
consumed/g/minute

178. Coloured fluid in manometer

179. What is the purpose
of the glass beads in
tube X?
Control
Suggest how a
temperature of 25C
could be obtained
simultaneously in
tube X and Y.
Place in a water bath

180. Respirometer

181. Respirometer

182. END OF PART 1