Respiratory ANSWER KEY
1. B
2. A
3. C
4. D
5. D
6. A
7. A
8. D
9. C
10. D
11. A
12. C
13. D
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
D
C
C
D
A
C
A
C
C
A
C
B
D
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
A
A
D
A
A
B
B
B
B
A
A
C
A
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
C
B
A
B
B
B
A
D
D
C
50. • The stretch receptors in the alveoli send signals to the medulla oblongata.
• The medulla oblongata stops the signals to the diaphragm and the intercostal muscles.
• The diaphragm relaxes. • The diaphragm moves up (back to dome shaped).
• The rib muscles relax. • The ribcage moves down and inwards.
• Air is pushed out of the lungs as the thoracic cavity decreases in size.
• Decreased size of the thoracic cavity results in increased pressure to force air out.
• The elastic lungs recoil to push the air out. (any four for 1 mark each)
51. a) • The diaphragm moves down to increase the volume of the thoracic cavity, decreasing pressure, causing air to rush
in. • The ribs move up and out to increase the volume of the thoracic cavity, decreasing pressure, causing air to rush into
the lungs.
b) • The medulla oblongata controls the breathing rate.
• The pleural membranes ensure that the thoracic cavity is sealed so that pressure remains low during breathing.
• They allow the lungs to move freely within the thoracic cavity.
• They reduce friction between lung tissue and the rib cage.
• They create a partial vacuum and negative pressure. any one for 1 mark
52. • The contraction of the diaphragm causes it to move down (flatten).
• The contraction of the rib muscles causes the rib cage to move up and out.
• Negative pressure within the pleural cavities causes the lungs to expand.
• The volume of the thoracic cavity increases.
• The pleural membranes seal the lungs, allowing them to inflate. any four for 1 mark each
53. • Wetness increases the diffusion rate of gases.
• Large surface area allows for greater gas exchange.
• Alveoli are one cell layer thick for ease of diffusion.
• Numerous blood vessels increase the efficiency of gas exchange.
• Lipoprotein layer decreases surface tension to prevent alveolar collapse.
• Capillaries are one cell layer thick for ease of diffusion.
• Made up of alveoli to maximize surface area to volume ratio.
• Alveoli are made up of simple squamus epithelium.
• Alveoli are surrounded by a rich capillary network which increases the rate of diffusion.
• The large number of alveoli allows for greater gas exchange.
• A neutral pH or more basic pH than tissues allows hemoglobin to bind more readily to O2 .
• Cooler temperature in the lungs than in the tissues allows hemoglobin to bind more readily to O2 .
• Mucus and cilia in the lungs move debris out of the lungs for more efficient gas exchange.
• The pleural membranes prevent friction to allow inflation of the lungs.
• Stretch receptors in the alveoli inhibit the medulla oblongata thus allowing exhalation to occur.
• The alveoli are flexible or elastic for ease of inflation.
54. a) H2O + CO2 (diffuse into the blood from the tissues)  H2CO3 (carbonic acid) H + and HCO3
 Hb+H+  HHb (the excess H ions produced from the water and carbon dioxide are taken up by the hemoglobin
forming reduced hemoglobin)
 HbO2 + Hb  O2 (the oxygen diffuses into the tissues)
 Occurs in a warm, acidic environment (relative to the lung capillaries)
 Hb + CO2  HbCO2
b) Hemoglobin takes up excess H+ ions forming reduced hemoglobin at the tissues.
Bicarbonate ions take up excess H+ ions at the lungs forming water and carbon dioxide.
Blood is buffered by a variety of substances (including Hb, HCO3 ± , HPO4 2±, etc.) which reduces the amount of H+ ions
and keeps the pH relatively constant.
55. a) • The breathing rate increases. (1 mark)
b) • The medulla oblongata detects an increase in carbon dioxide concentration. (1 mark)
• The medulla oblongata then sends out a nerve impulse that increases the rate of contractions of the diaphragm and
intercostal muscles. (1 mark)
56. a) oxygen combines with hemoglobin to form oxyhemoglobin (O2 + Hb  HbO2) (1 mark)
 carbaminohemoglobin releases carbon dioxide (HbCO2  Hb + CO2) (1 mark)
 bicarbonate ions combine with hydrogen ions to release carbon dioxide
b) Blood at the lung capillaries has a lower temperature.
 Blood at the lung capillaries has a higher pH / less acidic.
 Blood at the lung capillaries has a lower oxygen concentration.
 Blood at the lung capillaries has a higher carbon dioxide concentration.
 Low amounts of hemoglobin will reduce the amount of O2 diffused per minute.
 Changes in blood pressure and blood velocity will affect the rate of gas exchange. any two for 1 mark each
57. • They are moist which increases the rate of diffusion of gases.
• They are highly vascularized which allows more exchange of gases.
• The thin walls of the alveoli allow materials to be exchanged quickly and easily.
• A layer of lipoprotein reduces surface tension and prevents the alveoli from collapsing.
• They are small and number in the millions. This increases their surface area and allows for speedy gas exchange.
• Stretch receptors in their walls signal medulla oblongata to stop inhalation.
any three for 1 mark each
58. • Carbon dioxide concentrations in the blood increase because of increased cellular respiration due to exercising.
• The medulla oblongata detects the increased levels of carbon dioxide / hydrogen ions.
• The medulla oblongata sends an increasing number of impulses to the diaphragm and rib muscles causing them to contract
faster.
• Increased muscle activity needs ATP.
• Increased hydrogen ion & carbon dioxide concentration increases the breathing rate.
• Muscles need more glucose.
59. a) • The lungs have a higher (7.4) pH / the tissues have a lower (7.38) pH.
• The lungs are more basic / less acidic.
• The tissues are more acidic / less basic. any one for 1 mark
AND • The lungs have a lower (cooler) temperature / the
tissues have a higher (warmer) temperature.
b) • Oxygen is released more readily from hemoglobin due to the lower pH and the higher temperature.
• Hemoglobin is denatured and releases oxygen at a lower pH and a higher temperature. either one for 1 mark
c) • pH would decrease
• increased lactic acid concentration
• temperature would increase
• increased hydrogen ions (H+)
• more oxygen released from hemoglobin
• more waste (CO2 )
• decreased oxyhemoglobin (HbO2) in blood
• sweating causes decreased blood volume
• greater concentration of bicarbonate ions in blood
• blood velocity increases
• increased carbaminohemoglobin (HbCO2) produced
• increased solute concentration due to sweating
• more reduced hemoglobin (HHb) would be produced