chapter 13 question

New Biology – a modern approach 2Chapter 13: The human breathing system

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Structured Questions

Core Section

|!|EQA01300001|!|

Complete the following paragraph with suitable words selected from below:

lower enters increases higher leaves relax

contract dome-shaped flattened raise decreases

The movement of air over the respiration surface is called ventilation. During inspiration, the diaphragm

muscles (i)_______________ to make the diaphragm (ii)_______________. At the same time, the intercostal

muscles contract to (iii)_______________ the rib cage. The volume of the thoracic cavity

(iv)_______________. The air pressure inside the lungs becomes (v)_______________ than the atmospheric

pressure. As a result, air (vi)_______________ the lungs.

(3 marks)

##

(i) contract (1/2 mark)

(ii) flattened (1/2 mark)

(iii) raise (1/2 mark)

(iv) increases (1/2 mark)

(v) lower (1/2 mark)

(vi) enters (1/2 mark)

_________

(3 marks)##

|!|EQB01300002|!|

* Thomas examined the photomicrograph below that shows some cells from the lining of the respiratory tract:

________________________________________________________________________________________© Aristo Educational Press Ltd 2007 234

Layer A


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(i) Name TWO types of cells in layer A and state their functions which help to keep the respiratory tract

free from dust. (4 marks)

Name Function

(1)1 mark/ blank

(2)1 mark/ blank

(ii) In some cities in the Mainland China, the residents use coal as a fuel. In the air, there would be a higher

level of soot particles. State the effect of the soot particles on gaseous exchange in the lungs.

(2 marks)

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(iii) Bronchitis is the inflammation of the lining of the bronchi. State the result in a patient after repeated

attacks of bronchitis. (2 marks)

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(iv) People sometimes choke when trying to swallow pieces of poorly chewed food. Name a reflex action to

expel the food out of the windpipe. (1 mark)

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##

(i)

Name Function

(1) mucus-producing cells To produce mucus to trap dust.1 mark/ blank

(2) ciliated epithelial cells To sweep the mucus and dust towards the throat.1 mark/ blank

(ii) The soot particles in the alveoli reduce the surface area for gaseous exchange. (1 mark)

Thus the rate of gaseous exchange becomes slower if more soot particles are present in the lungs.

(1 mark)

(iii) The passageways of the bronchi become narrow, (1 mark)

making breathing more difficult. (1 mark)

(iv) Coughing. (1 mark)

_________

(9 marks)##

|!|EQB01300003|!|



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* Vivian was asked to put her right hand on the sternum and her left hand on the left side of the rib cage. Then

she breathed in and out. She found that both parts moved during the breathing action.

(i) On the diagram shown below, draw the position of the labeled parts after exhalation. (3 marks)

(ii) There are muscles in the diaphragm. Describe the role of these muscles in exhalation. (4 marks)

_______________________________________________________________________________

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_______________________________________________________________________________

(iii) During breathing, the ribs move. Name the muscles involved. (1 mark)

_______________________________________________________________________________

(iv) State the direction in which the ribs move during exhalation. (1 mark)

_______________________________________________________________________________


sternum

rib

diaphragm

backbone


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##

(i)

Correct position of sternum (1 mark)

Correct position of rib (1 mark)

Correct position of diaphragm (1 mark)

(ii) The diaphragm muscles relax and the diaphragm returns to dome-shaped. (2 marks)

This reduces the volume of the thorax and (1 mark)

the air pressure in the thorax increases. (1 mark)

(iii) intercostal muscles (1 mark)

(iv) The ribs move downwards and inwards. (1 mark)

_________

(9 marks)##

|!|EQA01300004|!|

Read the passage below and answer the questions that follow:

VOICEBOX

Your voice box (larynx) is a framework of cartilages, muscles and mucous membranes

that forms the entrance to your trachea (windpipe). The larynx is the part at the top of the

windpipe. The epiglottis is a small, movable lid just above the larynx that prevents food and

drinks from entering your windpipe. You cannot swallow and breathe at the same time. Don’t

talk too much when you are eating. Otherwise you may choke when food wrongly falls down

the trachea.


sternum

rib

diaphragm

backbone

During expiration


________________________________________________________________________________________

(i) Explain why swallowing and breathing cannot occur at the same time. (4 marks)

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

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(ii) The pharynx is the part which is common to the respiratory and digestive systems. Breathing through the

mouth is possible, but it is not a good habit. State the advantages of breathing through the nose.

(3 marks)

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_______________________________________________________________________________

_______________________________________________________________________________

(iii) Describe a structural feature which keeps the trachea constantly open. (1 mark)

_______________________________________________________________________________

(iv) In a human male, the larynx enlarges after puberty. Describe the change of his voice. (1 mark)

_______________________________________________________________________________

##

(i) The epiglottis drops down when one swallows, (1 mark)

effectively blocking the larynx. (1 mark)

If he is not eating, the epiglottis is slightly lifted (1 mark)

so that air can flow freely into the lungs. (1 mark)

(ii) The air is moistened by the mucous layer, (1 mark)

warmed by the blood vessels (1 mark)

and filtered by the cilia. (1 mark)

(iii) C-shaped cartilage (1 mark)

(iv) His voice becomes deeper. (1 mark)

_________

(9 marks)##



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|!|EQA01300005|!|

The following setup was used to examine the composition of air samples. Each time the gas jar was filled with

a treated air sample. The amount of the air sample before treatment was 15.0 cm3. The air sample entered the

syringe via the rubber tube. The volume of air sample collected was measured by the syringe.

Treatment Volume measured by syringe (cm 3 )

A. Inhaled air exposed to potassium hydroxide solution 15.0 cm3

B. Inhaled air exposed to alkaline pyrogallol 12.0 cm3

C. Exhaled air exposed to potassium hydroxide solution 14.5 cm3

(i) What was the function of potassium hydroxide? (1 mark)

_______________________________________________________________________________

(ii) Why did the volume measured for treatment A remain at 15.0 cm3? (3 marks)

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

(iii) What gas did alkaline pyrogallol absorb? Calculate the percentage of the gas in the air sample.

(2 marks)

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_______________________________________________________________________________

(iv) Compare the volumes measured for treatment A and treatment C. What conclusion can you draw from

the comparison? Explain the difference. (3 marks)

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##

(i) To absorb carbon dioxide. (1 mark)



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(ii) Since the percentage of carbon dioxide in the inhaled air was only about 0.03, (1 mark)

its volume in the 15cm3 air sample was too small (1 mark)

for its absorption to be measured by the syringe. (1 mark)

(iii) Oxygen. (1 mark)

[(15－12)/15]×100%(1)＝20% (1 mark)

(iv) The exhaled air has more carbon dioxide/ a higher percentage of carbon dioxide than inhaled air.

(1 mark)

Since carbon dioxide is produced by cells as a waste product of respiration, it is carried away from the

body during exhalation. (2 marks)

_________

(9 marks)##

|!|EQA01300006|!|

The diagram below shows a model of a human chest. Axis A is fixed while axis B can be moved up and down.

(i) Which part of the body does each of the following represent?

(1) axis A: ___________________

(2) axis B: ___________________

(3) strips of wood: ___________________

(4) rubber bands: ___________________ (4 marks)

(ii) What corresponding movement in the human body is demonstrated when axis B is moved up? (1

mark)

_______________________________________________________________________________



________________________________________________________________________________________

(iii) How is the movement in (ii) brought about in the human body? (1 mark)

_______________________________________________________________________________

_______________________________________________________________________________

(iv) What would happen to the lungs in the human body as a result of the movement in (ii)?

(1 mark)

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(v) Describe and explain the sequence of events involved in the process of inspiration. (6 marks)

_______________________________________________________________________________

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##

(i) (1) vertebral column (1 mark)

(2) sternum (1 mark)

(3) ribs (1 mark)

(4) intercostal muscles (1 mark)

(ii) The sternum is moved up/ rib cage is raised/ inspiration. (1 mark)

(iii) by the contraction of intercostal muscles (1 mark)

(iv) The volume of the lungs increases./ inflation of lungs (1 mark)

(v) Contraction of the intercostal muscles raises the rib cage. (1 mark)

Contraction of the diaphragm muscles flattens the diaphragm. (1 mark)

The volume of the thorax is increased. (1 mark)

The pressure inside the thorax is reduced. (1 mark)

Thus air is forced into the lungs (1 mark)

by the greater atmospheric pressure. (1 mark)

__________

(13 marks)##



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|!|EQB01300007|!|

* The diagram below shows the structure of the bronchiole and an alveolus in a human lung:

(i) State the function of

(1) cilia on the inner surface of the bronchiole. (2 marks)

_______________________________________________________________________________

_______________________________________________________________________________

(2) the water film on the inner surface of the alveolus. (1 mark)

_______________________________________________________________________________

(ii) Name TWO gases which are most abundant in the expired air. (1 mark)

_______________________________________________________________________________

(iii) Name gas X and gas Y. Name the process by which these gases pass through the alveolar wall into the

blood. (2 marks)

_______________________________________________________________________________

(iv) State TWO structures in the diagram that are defensive against inhaled bacteria. (2 marks)

_______________________________________________________________________________

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(v) Give THREE structural features of the alveoli which make the lungs efficient for gaseous exchange.

(3 marks)

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________________________________________________________________________________________

(vi) State the differences between the pulmonary artery and the pulmonary vein with reference to their

(1) structures. (1 mark)

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(2) composition of blood. (1 mark)

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_______________________________________________________________________________

(3) nature of haemoglobin in their red blood cells. (1 mark)

_______________________________________________________________________________

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(vii) Give FOUR reasons why it is healthier to breathe through the nose than through the mouth.

(4 marks)

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(viii) Explain how the presence of soot particles may affect gaseous exchange. (2 marks)

_______________________________________________________________________________

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(ix) Suggest a possible source of soot particles. (1 mark)

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##

(i) (1) The waving movement of cilia causes the mucus to mix with dust and bacteria and move upwards

from the bronchiole to the larynx. (2 marks)

(2) as a moist layer for dissolving oxygen (1 mark)

(ii) oxygen (½ mark)

nitrogen (½ mark)

(Composition of expired air: oxygen ........

…...16.4 %

nitrogen ......……79.6 %

carbon dioxide ...4.0 %)

(iii) Gas X = oxygen (1/2 mark)

Gas Y = carbon dioxide (1/2 mark)

diffusion (1 mark)

(iv) cilia for sweeping dust and bacteria (1 mark)



________________________________________________________________________________________

white blood cells to kill bacteria (1 mark)

(v) The wall is thin enough for rapid diffusion of gases. (1 mark)

The wall is moistened by water film for dissolving oxygen. (1 mark)

It is richly supplied with blood capillaries for transport of gases/

to maintain a steep concentration gradient across the alveolar wall. (1 mark)

(vi)

Pulmonary artery Pulmonary vein

(1)Structure

(2)Composition of blood

(3)Nature of haemoglobin

(1) Thicker wall/ with

more elastic tissue

(2) More carbon dioxide/ less

oxygen

(3) Carbaminohaemoglobin

(1) Thinner wall/ with less

elastic tissue

(2) More oxygen/ less

carbon dioxide

(3) Oxyhaemoglobin

(3 marks)

(vii) -Hair in the nasal passage can filter the dust. (1 mark)

-Mucus in the nasal passage can trap the bacteria. (1 mark)

-Pressure of sensory cells in the nasal cavity prevents the breathing of harmful gases into the lungs. (1

mark)

-The blood capillaries in the nasal cavity warm the incoming air before it enters the lungs.

(1 mark)

(viii) Soot particles slow down the rate of gaseous exchange by depositing on the inner surface of alveoli

which increases the distance of gas diffusion/ reducing the surface area of the respiratory surface.

(2 marks)

(ix) The soot particles may come from smoking/ exhaust fumes. (1 mark)

__________

(21 marks)##

|!|EQA01300008|!|

The following table shows the results obtained from the analysis of an air sample:

Volume (cm 3 )

Original volume of the air sample

Volume after absorbing carbon dioxide

Volume after absorbing oxygen and carbon dioxide

100

96

80

(i) Name a chemical which could be used in this experiment to absorb carbon dioxide. (1 mark)

_______________________________________________________________________________

(ii) Calculate the percentages of carbon dioxide and oxygen in the air sample. (4 marks)



________________________________________________________________________________________

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(iii) Was this sample taken from inspired or expired air? Give a reason for your answer. (2 marks)

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(iv) Explain why great care had to be taken to avoid any change in temperature during the analysis of the

air sample. (2 marks)

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##

(i) caustic soda/ sodium hydroxide/ potassium hydroxide (1 mark)

(ii) The percentage of carbon dioxide = x 100% = 4% (2 marks)

The percentage of oxygen = x 100% = 16% (2 marks)

(iii) Expired air - because it contained more than 0.03% carbon dioxide (2 marks)

(iv) The air expanded when the temperature increased. (1 mark)

Thus the volumes would not be comparable. (1 mark)

_________

(9 marks)##



________________________________________________________________________________________

|!|EQB01300009|!|

* The following diagram shows the respiratory system in man:

(i) Name parts A to F. (3 marks)

A. ____________________ B. ____________________ C. ____________________

D. ____________________ E. ____________________ F. ____________________

(ii) State and explain TWO adaptive features possessed by B to perform its function. (4 marks)

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(iii) How is E adapted for gaseous exchange? State the importance of these adaptations. (4 marks)

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(iv) State and explain the status of F when the man inspires. (2 marks)

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________________________________________________________________________________________

(v) Name X and state its function. (2 marks)

_______________________________________________________________________________

_______________________________________________________________________________

(vi) State and explain what will happen if D is punctured in an accident. (3 marks)

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##

(i) A - nasal cavity

B - trachea

C – bronchus

D - pleura/ pleural membranes

E - alveolus/air sac

F – diaphragm (½ mark each) (3 marks)

(ii) It is supported by incomplete rings of cartilage/ C-shaped cartilage (1 mark)

which can keep the trachea open all the time. (1 mark)

Its inner lining produces mucus and is covered with cilia. (1 mark)

These can trap dust particles and germs and remove them from the respiratory tract. (1 mark)

(iii) E is highly folded/ lobed (1 mark)

to increase the surface area for diffusion of gases. (1 mark)

Its wall is thin/ one-cell thick (1 mark)

to shorten the distance for the diffusion of gases. (1 mark)

(iv) When the man inspires, his diaphragm muscle contracts and the diaphragm/ F becomes flattened.

(1 mark)

As a result it increases the volume of the thorax/ decreases the pressure inside the thorax. (1 mark)

(v) X is pleural fluid which reduces friction during breathing. (2 marks)

(vi) Air leaks into the pleural cavity. (1 mark)

The lungs collapse (1 mark)

because of their own elasticity. (1 mark)

__________

(18 marks)##

|!|EQA01300010|!|

The following diagram illustrates a model used to show the breathing mechanism of mammals:



________________________________________________________________________________________

(i) Name the structure in the human body corresponding to

(1) glass tube B. _____________________ (1 mark)

(2) the balloons. _____________________ (1 mark)

(ii) Explain why

(1) the rubber sheet cannot accurately represent the diaphragm in breathing movements. (4 marks)

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

(2) the bell jar cannot accurately represent the thoracic wall. (2 marks)

_______________________________________________________________________________

_______________________________________________________________________________

(3) glass tube A cannot accurately represent the trachea. (4 marks)

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________



________________________________________________________________________________________

(iii) (1) Which structure of the mammalian body is represented by space X in the diagram? (1 mark)

_______________________________________________________________________________

(2) Name the fluid contained in this structure. (1 mark)

_______________________________________________________________________________

##

(i) (1) bronchus (1 mark)

(2) lungs (1 mark)

(ii) (1)

Rubber sheet Diaphragm

any two pairs

- Flat when at rest

- Movement is controlled

by hand

- Moves downwards to fill

balloons with air

- Dome -shaped when at rest

- Movement is automatic

- Flattens during inspiration

(4 marks)

(2) The bell jar is rigid/ immovable/ not elastic while the ribs can move during breathing. (2 marks)

(3) The trachea is elastic and cilia are present in the inner lining while glass tube A is rigid and has no

cilia. (4 marks)

(iii) (1) thoracic cavity/pleural cavity/chest cavity (1 mark)

(2) pleural fluid (1 mark)

__________

(14 marks)##

|!|EQB01300011|!|

STS Connections

* The diagrams below show the field of view of a microscope for observing the bronchioles and alveoli of two

persons:


Person A Person B


________________________________________________________________________________________

(i) Which of the two persons, A or B, is a smoker? (1 mark)

_______________________________________________________________________________

(ii) With reference to the diagram, what are the TWO structural differences between the lungs of person A

and those of person B? (2 marks)

_______________________________________________________________________________

_______________________________________________________________________________

(iii) In what way would the differences in (ii) affect the functioning of the lungs? (2 marks)

_______________________________________________________________________________

_______________________________________________________________________________

(iv) The diagram below shows an alveolus of person A as observed under a high-power microscope:

(1) With reference to the diagram, what are the adaptations of the alveolus for gaseous exchange?

(3 marks)

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

(2) Write the route taken by oxygen to pass from space Y into cell X. (2 marks)

_______________________________________________________________________________

_______________________________________________________________________________

##

(i) Person B (1 mark)

(ii)

Person A Person B

The folding of alveoli is normal.

The diameter of bronchioles is wide.

The folding of alveoli disappears.

The bronchioles are constricted.

(1 mark each) (2 marks)

(iii) For person B, the surface area for gaseous exchange decreases due to potential disappearance of the

folding in alveoli. (1 mark)



________________________________________________________________________________________

In addition, person B has difficulty in breathing in or out due to the narrow passage at the bronchioles.

(1 mark)

(iv) (1) The wall of the alveolus is one-cell thick to shorten the distance for the diffusion of gases.

(1 mark)

The lining is moist to dissolve the gases for diffusion (1 mark)

The alveolus is surrounded by a network of capillaries. The blood carries the gases to and away

from the alveolus to increase the concentration gradient for diffusion. (1 mark)

(2) moisture on the wall of the alveolus wall of the alveolus wall of the blood capillary

cell membrane of cell X cell X (2 marks)

__________

(10 marks)##

Extension Section



________________________________________________________________________________________

|!|EQA01300012|!|

STS Connections

Aaron participated in a survey to measure the volume of air flowing into and out of his lungs. The graph

below shows the volume of air in his lungs while breathing at rest:

(i) Find out the volume of air breathed out in one breath. (1 mark)

_______________________________________________________________________________

(ii) Calculate Aaron’s breathing rate. Show your working. (2 marks)

_______________________________________________________________________________

_______________________________________________________________________________

(iii) Calculate the volume of air breathed out in one minute. (1 mark)

_______________________________________________________________________________



________________________________________________________________________________________

(iv) Describe the effect of exercise on:

(1) the depth of each breath; (1 mark)

_______________________________________________________________________________

(2) the rate of breathing. (1 mark)

_______________________________________________________________________________

(v) During vigorous exercise, both aerobic respiration and anaerobic respiration take place. Compare the

two types of respiration. (3 marks)

Aerobic respiration Anaerobic respiration

(1) Products

formed

1 mark each

(2) Amount of

energy

1/2 mark each

##

(i) 0.5 dm3 (1 mark)

(ii) Aaron’s breathing rate = 4 x 60/15 (1 mark)

= 16 breaths per minute (1 mark)

(iii) Volume of air breathed out in one minute = 0.5 x 16 = 8 dm3 (1 mark)

(iv) (1) The depth of each breath is increased. (1 mark)

(2) The rate of breathing is faster. (1 mark)

(v)

Aerobic respiration Anaerobic respiration

(1) Products

formed

water & carbon dioxide lactic acid 1 mark each

(2) Amount of

energy

larger smaller 1/2 mark each

_________

(9 marks)##

|!|EQA01300013|!|

A boy was allowed to breathe in three types of gases. His breathing rate with each type of gas is shown below:

Type of gas Breathing rate (no. of breaths per min.)

A. 20% oxygen + 0.03% carbon dioxide 18

B. 95% oxygen 10

C. 93% oxygen + 2.2% carbon dioxide 25



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(i) Which substance, oxygen or carbon dioxide, had a greater effect on the breathing rate? Explain briefly.

(3 marks)

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

(ii) Describe how this substance stimulated the breathing rate. (4 marks)

_______________________________________________________________________________

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_______________________________________________________________________________

_______________________________________________________________________________

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_______________________________________________________________________________

(iii) Without using this substance, how could he increase his breathing rate consciously? (2 marks)

_______________________________________________________________________________

_______________________________________________________________________________

(iv) Choose a gas from the above types (A, B or C) to apply to a person with breathing difficulty. Explain

your choice. (3 marks)

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

##

(i) Carbon dioxide. (1 mark)

By comparing the breathing rate for types B and C, which contained similar percentages of oxygen, it

was found that the breathing rate for type C was much higher than that of type B. (1 mark)

This indicates that the difference was due to the presence of carbon dioxide. (1 mark)

(ii) Breathing in more carbon dioxide led to an increase in carbon dioxide concentration in blood and hence

a decrease in the blood pH. (1 mark)

The change was detected by chemoreceptors (1 mark)

which then sent nerve impulses to the respiratory centre. (1 mark)

It then sent more nerve impulses to the diaphragm muscles and intercostal muscles to make them

contract more frequently. (1 mark)

(iii) Move the intercostal muscles and diaphragm muscles more quickly. (2 marks)

(iv) Type C. (1 mark)

It has a high carbon dioxide content which can lower blood pH, stimulating the patient to breathe faster

(1 mark)



________________________________________________________________________________________

to get more oxygen, and the gas also supplies a high percentage of oxygen. (1 mark)

__________

(12 marks)##

|!|EQA01300014|!|

An experiment was carried out by a student to measure the volume of air taken in per breath and the number

of breaths per minute at rest and after exercise. The results are shown as follows:

Volume of air per breath Breaths per minute

At rest 400 cm3 20

Just after exercise 900 cm3 36

(i) Calculate the total volume of air breathed in per minute

(1) at rest. (1 mark)

_______________________________________________________________________________

__________________________________________________________________

(2) just after exercise. (1 mark)

_______________________________________________________________________________

_______________________________________________________________________________

(ii) Assuming that the air breathed in consists of 20% oxygen and the air breathed out consists of 16%

oxygen, calculate the volume of oxygen entering the blood per minute when the student was

(1) at rest. (1 mark)

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

(2) just after exercise. (1 mark)

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

(iii) From the data in the table, state the effect of exercise on breathing. (2 marks)

_______________________________________________________________________________

_______________________________________________________________________________

(iv) In order to bring about the changes in (iii) during exercise, state

(1) the part of the nervous system involved. (1 mark)

_______________________________________________________________________________

_______________________________________________________________________________

(2) the stimulus concerned. (1 mark)

_______________________________________________________________________________



________________________________________________________________________________________

_______________________________________________________________________________

(3) the TWO effectors responsible. (2 marks)

_______________________________________________________________________________

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##

(i) (1) At rest = 8000 cm3 (1 mark)

(2) Just after exercise = 32400 cm3 (1 mark)

(ii) (1) At rest = 8000 x 4% = 320 cm3 (1 mark)

(2) Just after exercise = 32400 x 4% = 1296 cm3 (1 mark)

(iii) During exercise the rate and depth of breathing increase. (2 marks)

(iv) (1) medulla oblongata (1 mark)

(2) high concentration of CO2 (1 mark)

(3) diaphragm muscle and intercostal muscle (2 marks)

__________

(10 marks)##

|!|EQA01300015|!|

A man breathed into and out of an air-tight bag which was filled with air initially. His nose was clipped so that

the air getting into his body could only come from the bag.



________________________________________________________________________________________

(i) What would happen to the rate and depth of breathing of the man? (2 marks)

_______________________________________________________________________________

_______________________________________________________________________________

(ii) Explain why and how the changes in (i) occurred. (4 marks)

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

##

(i) Both the rate and depth of breathing increased. (2 marks)

(ii) Carbon dioxide accumulated in the body. (1 mark)

The blood pH was lowered and this stimulates the breathing centre of the medulla oblongata

(1 mark)

to send off nerve impulses to the diaphragm muscle and intercostal muscles (1 mark)

so as to increase the rate and depth of breathing for expelling the carbon dioxide. (1 mark)

_________

(6 marks)##


chapter 13 question

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