Chapter 18 - Gas Exchange and Transport

Human Physiology: An Integrated Approach, 6e (Silverthorn)

Chapter 18 Gas Exchange and Transport

1) High carbon dioxide concentration in body fluids is called

A) carbonation.

B) hyperdioxia.

C) hyperoxia.

D) hypercarbia.

E) hypercapnia.

: E

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.4

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

2) The partial pressure of oxygen in arterial blood is approximately ________ mm Hg.

A) 40

B) 45

C) 50

D) 70

E) 100

: E

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.4

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

3) The partial pressure of carbon dioxide in the cells of peripheral tissues is approximately ________ mm Hg.

A) 40

B) 45

C) 50

D) 70

E) 100

: B

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.5

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

4) Of the factors that influence diffusion of respiratory gases, the most variable and, therefore, important factor to consider is the

A) concentration gradient.

B) diffusion distance.

C) membrane surface area.

D) membrane thickness.

E) electrical charge.

: A

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

5) The process by which dissolved gases are exchanged between the blood and interstitial fluids is

A) pulmonary ventilation.

B) external respiration.

C) diffusion.

D) cellular respiration.

E) breathing.

: C

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

6) The lung pathology most likely to result from certain kinds of heart disease is

A) emphysema.

B) asthma.

C) pulmonary edema.

D) fibrotic lung disease.

E) lung cancer.

: C

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

7) Hypoxia resulting from fluid accumulation in the alveoli that cannot be corrected by oxygen therapy can lead to

A) emphysema.

B) fibrotic lung disease.

C) asthma.

D) adult respiratory distress syndrome.

E) sudden infant death syndrome.

: D

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

8) If the partial pressure of oxygen in both air and water is 100 mm Hg, then the concentration of the oxygen is the same in the air and water.

A) True

B) False

: B

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.2

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

9) The variables of oxygen consumption, cardiac output, and blood oxygen content are unrelated.

A) True

B) False

: B

Section Title: Gas Transport in the Blood

Learning Outcome: 18.5

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

10) Which of the following characteristics makes hemoglobin's structure such a good match for its function as an oxygen carrier?

A) Each hemoglobin molecule can bind one oxygen molecule.

B) Each hemoglobin molecule can bind two oxygen molecules.

C) Each hemoglobin molecule can bind four oxygen molecules.

D) Each hemoglobin molecule can't be saturated by oxygen molecules.

E) Each hemoglobin binds irreversibly to an oxygen molecule.

: C

Section Title: Gas Transport in the Blood

Learning Outcome: 18.6

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

11) Most of the oxygen transported by the blood is

A) dissolved in plasma.

B) bound to hemoglobin.

C) in ionic form as solute in the plasma.

D) bound to a plasma protein.

E) carried by white blood cells.

: B

Section Title: Gas Transport in the Blood

Learning Outcome: 18.7

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

12) At a PO2 of 70 mm Hg and normal temperature and pH, hemoglobin is ________% saturated with oxygen.

A) 10

B) 25

C) 50

D) 75

E) over 90

: E

Section Title: Gas Transport in the Blood

Learning Outcome: 18.7

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

13) Which of the following would make the oxygen-hemoglobin curve shift right?

A) increased H+ concentration

B) increased pH

C) decreased temperature

D) decreased CO2

E) None of the answers are correct.

: A

Section Title: Gas Transport in the Blood

Learning Outcome: 18.8

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

14) Chronic hypoxia

A) increases 2,3-DPG production in blood.

B) shifts the HbO2 dissociation curve to the left.

C) can be caused by anemia.

D) increases 2,3-DPG production in blood and can result from anemia.

E) All of the answers are correct.

: D

Section Title: Gas Transport in the Blood

Learning Outcome: 18.8

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

15) Most of the carbon dioxide in the blood is transported as

A) solute dissolved in the plasma.

B) carbaminohemoglobin.

C) bicarbonate ions.

D) solute dissolved in the cytoplasm of red blood cells.

E) carbonic acid.

: C

Section Title: Gas Transport in the Blood

Learning Outcome: 18.3

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

16) In the medulla oblongata, the nucleus tractus solitarius contains the ________ of neurons.

A) pontine respiratory group

B) ventral respiratory group

C) dorsal respiratory group

D) pre-Botzinger complex

: C

Section Title: Regulation of Ventilation

Learning Outcome: 18.14

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

17) The most important chemical regulator of respiration is

A) oxygen.

B) carbon dioxide.

C) bicarbonate ion.

D) sodium ion.

E) hemoglobin.

: B

Section Title: Regulation of Ventilation

Learning Outcome: 18.14

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

18) An increase in the level of carbon dioxide in the blood will

A) decrease the rate of breathing.

B) increase the rate of breathing.

C) decrease pulmonary ventilation.

D) decrease the alveolar ventilation rate.

E) increase the pH of arterial blood.

: B

Section Title: Regulation of Ventilation

Learning Outcome: 18.15

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

19) The expiratory neurons control the ________ muscles, whereas the inspiratory neurons control the ________ muscles.

A) diaphragm and external intercostal, abdominal and internal intercostal

B) abdominal and internal intercostal, diaphragm and external intercostal

C) diaphragm and internal intercostal, abdominal and external intercostal

D) abdominal and external intercostal, diaphragm and internal intercostal

E) diaphragm and abdominal, intercostal internal and external

: B

Section Title: Regulation of Ventilation

Learning Outcome: 18.14

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

20) If the neural connections between the pons and medulla are severed, breathing will stop.

A) True

B) False

: B

Section Title: Regulation of Ventilation

Learning Outcome: 18.14

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

21) The Hering-Breuer reflex

A) functions to increase ventilation with changes in blood pressure.

B) alters pulmonary ventilation when the PO2 changes.

C) alters pulmonary ventilation when the PCO2 changes.

D) prevents overexpansion of the lungs.

E) is an important aspect of normal, quiet breathing.

: D

Section Title: Regulation of Ventilation

Learning Outcome: 18.16

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

22) Protective reflexes of the lungs include

A) coughing.

B) bronchoconstriction.

C) bronchodilation.

D) bronchodilation and coughing.

E) coughing and bronchoconstriction.

: E

Section Title: Regulation of Ventilation

Learning Outcome: 18.16

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

Match the lung disease to its description.

A. fibrotic lung disease

B. emphysema

C. asthma

D. pulmonary edema

23) destruction of alveoli

: B

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

24) thickened alveolar membrane and decreased lung compliance

: A

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

25) decreased surface area for gas exchange

: B

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

26) increased airway resistance

: C

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

27) fluid accumulation in interstitial spaces

: D

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

28) increased diffusion distance

: D

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

Match the factor with its effect on the affinity of hemoglobin for oxygen.

A. increase

B. decrease

29) increased temperature

: B

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.8

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

30) increased pH

: A

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.8

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

31) increased PCO2

: B

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.8

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

32) increased 2,3-DPG

: B

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.8

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

33) Too little oxygen in cells is called ________.

: hypoxia

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

34) Too little oxygen in cells is often accompanied by too much ________, which is called ________.

: carbon dioxide, hypercapnia

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

35) Generally, PO2 in arterial blood is ________ than PO2 in venous blood.

: higher

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.4

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

36) Generally, PCO2 in arterial blood is ________ than PCO2 in venous blood.

: lower

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.4

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

37) PCO2 tends to be ________ in tissues than in systemic capillaries.

: higher

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.4

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

38) Diffusion rate is directly proportional to ________ and ________.

: surface area, concentration gradient

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

39) ________ is characterized by a decreased surface area for gas exchange in the lungs.

: Emphysema

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

40) ________ is characterized by a thickened alveolar membrane, slowing respiratory gas exchange.

: Fibrotic lung disease

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

41) In ________, fluid accumulates in the interstitial spaces of the lungs, slowing gas exchange.

: pulmonary edema

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

42) ________ is characterized by an increased airway resistance and decreased ventilation.

: Asthma

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

43) Diffusion rate is indirectly proportional to ________.

: membrane thickness

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

44) ________ is the enzyme that converts CO2 into bicarbonate ions.

: Carbonic anhydrase

Section Title: Gas Transport in the Blood

Learning Outcome: 18.11

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

45) The ________ group of neurons contains mostly inspiratory neurons. The ________ group of neurons controls muscles used for active expiration and some inspiratory muscles.

: dorsal respiratory; ventral respiratory

Section Title: Regulation of Ventilation

Learning Outcome: 18.14

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

46) The output of the ________ group of inspiratory neurons controls the ________ muscle(s) by way of the ________ nerve.

: dorsal respiratory, diaphragm (or internal intercostal), phrenic (or intercostal)

Section Title: Regulation of Ventilation

Learning Outcome: 18.14

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

47) Inappropriate relaxation of the ________ muscles during sleep contributes to ________, a sleep disorder associated with snoring.

: mouth and throat (larynx, pharynx, and tongue), obstructive sleep apnea

Section Title: Regulation of Ventilation

Learning Outcome: 18.14

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

48) Specialized ________ in the carotid and aortic bodies are activated by a decrease in PO2 and pH or an increase in PCO2. What do they trigger?

: glomus cells; they trigger a reflex increase in ventilation.

Section Title: Regulation of Ventilation

Learning Outcome: 18.15

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

49) The carotid and aortic bodies contain specialized ________ cells, which can increase ventilation in response to changes in PO2, PCO2, or pH.

: glomus

Section Title: Regulation of Ventilation

Learning Outcome: 18.15

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

50) Fear and excitement may affect the pace and depth of respiration by stimulation of portions of the ________.

: limbic system

Section Title: Regulation of Ventilation

Learning Outcome: 18.17

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

51) What force(s) move(s) carbon dioxide from the blood into the alveoli?

: Carbon dioxide moves into the alveoli as a result of the pressure gradient.

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

52) List and explain the factors that influence gas diffusion in the lungs.

: Concentration gradient, surface area, membrane thickness, and diffusion distance are the four factors. Increasing the concentration gradient and surface area will increase the rate of diffusion across the lungs while increasing membrane thickness and diffusion distance will decrease the rate of diffusion in the lungs. This is discussed in the "Diffusion and Solubility of Gases" section of the chapter.

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

53) Name three pathological changes that adversely affect gas exchange.

: 1. a decrease in the amount of alveolar surface area available for gas exchange

2. an increase in the thickness of the alveolar membrane

3. an increase in the diffusion distance between the alveoli and the blood

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

54) List and explain the factors that influence the presence of gases in liquids.

: Pressure, solubility, and temperature are three factors. This is discussed in "The Solubility of Gases in Liquids Depends on Pressure, Solubility, and Temperature" section of the chapter.

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.2

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

55) What are the three ways CO2 is transported in blood? Approximately what percentage is transported by each way?

: 1. attached to hemoglobin, 23%

2. dissolved, 7%

3. as bicarbonate, 70%

Section Title: Regulation of Ventilation

Learning Outcome: 18.13

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

56) What are the PO2 and PCO2 in the alveoli, artery, peripheral tissue, and veins?

Explain why the PO2 and PCO2 change.

: See Figure 18.2 and the "Gas Exchange in the Lungs and Tissues" section of the chapter.

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.5

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

57) Jill lives in St. Louis, which is close to sea level. She decides to spend a month of her summer vacation working in the mountains outside of Denver. After a week in the mountains, what kinds of changes would you expect to see as Jill adapts to the higher altitude?

A) decreased hematocrit

B) decreased blood pressure

C) decreased alveolar ventilation rate

D) decreased PO2 in the alveoli

E) All of the answers are correct.

: D

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

58) Carbon dioxide is more soluble in water than oxygen. To get the same amount of oxygen to dissolve in plasma as carbon dioxide, you would have to

A) decrease the temperature of the plasma.

B) increase the partial pressure of oxygen.

C) decrease the partial pressure of nitrogen.

D) increase the rate of plasma flow through the lungs.

E) decrease the alveolar ventilation rate.

: B

Section Title: Regulation of Ventilation

Learning Outcome: 18.3

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

59) For maximum efficiency in loading oxygen at the lungs,

A) the pH should be slightly acidic.

B) the temperature should be slightly lower than normal body temperature.

C) the PO2 should be about 70 mm.

D) DPG levels in the red blood cells should be high.

E) All of the answers are correct.

: B

Section Title: Gas Transport in the Blood

Learning Outcome: 18.8

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

60) A student in your lab volunteers to enter a hypoxic breathing chamber for 10 minutes, and his alveolar PO2 drops to 50 mm Hg. What other change would occur?

A) decrease in arterial pH

B) decrease in arterial PCO2

C) decrease in pH of cerebrospinal fluid

D) increase in alveolar PCO2

E) hypoventilation

: B

Section Title: Gas Transport in the Blood

Learning Outcome: 18.8

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

61) A molecule that blocks the activity of carbonic anhydrase would

A) interfere with oxygen binding to hemoglobin.

B) cause an increase in blood pH.

C) increase the amount of bicarbonate formed in the blood.

D) decrease the amount of carbon dioxide dissolved in the plasma.

E) All of the answers are correct.

: B

Section Title: Gas Transport in the Blood

Learning Outcome: 18.12

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

62) The chloride shift occurs when

A) hydrogen ions leave the red blood cells.

B) hydrogen ions enter the red blood cells.

C) bicarbonate ions enter the red blood cells.

D) bicarbonate ions leave the red blood cells.

E) carbonic acid is formed.

: D

Section Title: Regulation of Ventilation

Learning Outcome: 18.13

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

63) Blocking afferent action potentials from the chemoreceptors in the carotid and aortic bodies would interfere with the brain's ability to regulate breathing in response to all EXCEPT which of the following?

A) changes in PCO2

B) changes in PO2

C) changes in pH due to carbon dioxide levels

D) changes in blood pressure

E) All of the answers are correct.

: D

Section Title: Regulation of Ventilation

Learning Outcome: 18.15

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

64) Describe the different causes of hypoxia, and give specific examples of the associated conditions.

: See Table 18.1 in the chapter.

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

65) What are the two possible causes of lower alveolar PO2? Give examples of each.

:

1. The composition of the inspired air is abnormal. Altitude affects oxygen content of air.

2. Alveolar ventilation is inadequate. Pathological factors include increased airway resistance (asthma), decreased lung compliance (fibrosis), and overdoses of drugs or alcohol.

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

66) Describe the problems that result in low arterial oxygen content.

: Three categories of problems are inadequacies in oxygen reaching alveoli, oxygen exchange between the alveoli and blood, and transport of oxygen in the blood.

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

67) Compare and contrast the pulmonary pathologies that affect alveolar ventilation and gas exchange.

: See Figure 18.3c in the chapter, which discusses emphysema, fibrotic lung disease, pulmonary edema, and asthma.

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

68) Explain how oxygen and carbon dioxide are transported in the blood. How does the means of transport relate to the solubility and chemical reactivity of these gases in plasma?

: Oxygen is not highly soluble in water, which is the main component of plasma. Less than 2% is dissolved in plasma, with the remainder bound to hemoglobin. The iron in the heme portion of the molecule can bind up to four oxygen atoms. Oxygen is not chemically reactive in the body. Carbon dioxide is more soluble than oxygen, at about 7% dissolved. Carbon dioxide is chemically reactive, combining with water to form carbonic acid, which then dissociates to bicarbonate and hydrogen ion. Most carbon dioxide is transported in the form of bicarbonate, about 70%, and the remaining 23% binds to amino acids on hemoglobin.

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.3

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

69) List, compare, and contrast the brain's centers for monitoring and controlling respiration.

: Respiratory neurons in the medulla control inspiration and expiration. Neurons in the pons modulate ventilation. The rhythmic pattern of breathing arises from a network of spontaneously discharging neurons. Ventilation is subject to modulation by various chemical factors and by higher brain centers.

Section Title: Regulation of Ventilation

Learning Outcome: 18.14

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

70) List, compare, and contrast the locations and stimuli for respiratory chemoreceptors.

: Peripheral chemoreceptors in the carotid and aortic bodies sense changes in oxygen concentration, pH, and PCO2 of the plasma. Central chemoreceptors monitor cerebrospinal fluid composition and respond to changes in the concentration of CO2 in the cerebrospinal fluid.

Section Title: Regulation of Ventilation

Learning Outcome: 18.5

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

71) Draw a flow chart that shows the components of the reflex in which an increase in blood PCO2 leads to increased ventilation.

: Peripheral chemoreceptors in carotid and aortic bodies detect changes in PCO2 and pH. Central chemoreceptors in the medulla oblongata monitor CO2 in CSF. Either an increase in PCO2 or decrease in pH will stimulate the receptors, which project to a control center in the medulla oblongata. The control center stimulates somatic motor neurons that control the skeletal muscles involved in ventilation. The effect is increased ventilation, which lowers PCO2 by eliminating CO2, so blood pH increases because of this shift. See Figure 18.17 in the chapter.

Section Title: Regulation of Ventilation

Learning Outcome: 18.15

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

72) An industrious 10-year-old swimmer has attached an extension to his snorkel tube, so that he can sit on the bottom of the ocean for a longer period of time, watching the fish of the coral reef. What problems would you expect him to have? Assuming he is successful in breathing this way for a little while, what are some of the differences he will experience compared to normal breathing?

: The resistance to air flow increases as a result of adding the extension to the snorkel tube. Assuming he has used an extension of sufficiently large diameter, he is in a shallow location where the total length isn't excessive, and he has the strength and endurance in his respiratory muscles, he may be able to breathe this way for a few seconds longer than he could have held his breath. He will probably notice that he is breathing more deeply and at a higher rate, to maintain ventilation against the higher resistance. After a few exchanges he will start to hypoventilate, despite his efforts to increase pulmonary ventilation, because the presence of dead airspace in the tube will result in decreasing PO2 in the alveoli. Dead airspace is a problem if the total volume of air in the tube is greater than the volume exchanged with each breath.

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.1

: Level III: Problem Solving (Bloom's Taxonomy: Synthesis)

73) Drowning is often the introduction of outside water into the alveoli, yet some water is normally present in alveoli. Why is water normally present in the alveoli? What is present in alveolar fluid, besides water, that aids in respiration? What properties of water are detrimental to respiration? What causes drowning? While extremely rare, there have even been documented cases of people walking away from recreational swimming only to die later, on dry land, as a result of drowning (termed "delayed" or "secondary" drowning). Propose an explanation for delayed drowning.

: Water is present everywhere in living tissues, because all living cells require water as a diffusion medium for solutes. Alveolar fluid is present in only a thin layer because it contains surfactant, preventing it from collapsing the alveoli due to surface tension. Oxygen has low solubility in water, but the large total surface area of alveoli combined with the thinness of the water layer in the alveoli allows for sufficient oxygen to enter the blood. Inhalation of water increases the amount of water and decreases the relative amount of surfactant. Less oxygen will reach the alveolar membranes, and alveoli will collapse. Alveolar collapse combined with the low solubility of oxygen in water will lead to hypoxemia and will trigger cardiovascular and respiratory reflexes. Delayed drowning likely results from tissue damage in the lungs and malfunction in other organs resulting from hypoxemia and reflexes related to the water inhalation.

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.2

: Level III: Problem Solving (Bloom's Taxonomy: Synthesis)

74) In the science fiction movie The Abyss, a diver is able to breathe while his head is immersed in a specially prepared liquid pumped into a water-tight helmet attached to a suit, thus allowing him to dive without an air tank and at greater depths than possible for scuba divers. Is this purely fiction, or is it at least theoretically possible? Explain, considering the nature of alveoli and alveolar gas exchange. Assuming it is possible, describe the composition and nature of the liquid in terms of its oxygen pressure and concentration.

: (Note to instructor: Such experiments were done in the 1960s with rodents, and were partially successful but ultimately deemed impractical and too risky for humans.) It is theoretically possible. Oxygen dissolves in a thin film of fluid in the alveoli, thus even in normal breathing a liquid containing dissolved oxygen is involved. Obviously the respiratory gases would have to be soluble in this liquid and in concentrations appropriate to maintain the partial pressures necessary to drive diffusion.

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.3

: Level III: Problem Solving (Bloom's Taxonomy: Evaluation)

75) Do the factors affecting affinity of hemoglobin for oxygen have the same impact on loading and unloading in lungs and tissues? Explain your answer, and indicate if this presents a conflict in remedying hypoxia. Assuming a medical team has treatments available for changing all the factors affecting hemoglobin's oxygen affinity, how should they manipulate pH, temperature, PCO2, and 2,3-DPG content in a hypoxic patient?

: Hemoglobin affinity changes in the same way in the lungs and tissues, thus increasing unloading in the tissues does decrease loading in the lungs, which seems as if one cancels out the other. But from the oxygen dissociation curves it is evident that the impact is greater in the tissues; thus increased unloading can remedy hypoxia. The medical team should decrease pH, increase temperature, increase PCO2, and increase 2,3-DPG.

Section Title: Regulation of Ventilation

Learning Outcome: 18.7

: Level III: Problem Solving (Bloom's Taxonomy: Application)

76) Hemoglobin binds to and has a much higher affinity for carbon monoxide (CO) than for oxygen. CO is colorless and odorless and can be produced in homes heated by natural gas; victims usually do not realize they are being poisoned and often die in their sleep. Describe the likely changes in a CO poisoning victim.

: CO will gradually displace O2 on hemoglobin molecules. While this increases O2 unloading in tissues, it will significantly decrease O2 loading in lungs, therefore hypoxia will result. Victims gradually lose consciousness as the brain tissues become hypoxic.

Section Title: Gas Transport in the Blood

Learning Outcome: 18.10

: Level III: Problem Solving (Bloom's Taxonomy: Application)

77) Compare and contrast carbon monoxide (CO) poisoning, in which CO displaces oxygen from hemoglobin, and metabolic poisoning such as by cyanide.

: Both types of poisoning interfere with oxygen-dependent metabolism and thus can be fatal. CO prevents oxygen loading at the lungs and thus produces hypoxia. Metabolic poisons exert their effects on the chemical reactions that consume oxygen to produce ATP, and thus have no effect on PO2.

Section Title: Gas Exchange in the Lungs and Tissues

Learning Outcome: 18.10

: Level III: Problem Solving (Bloom's Taxonomy: Synthesis)

78) Write the chemical equation catalyzed by the enzyme carbonic anhydrase. Suppose the concentration of H+ is increased by an outside force in a solution that had been at equilibrium. According to the law of mass action, what must happen to the CO2 concentration to reestablish equilibrium after this disturbance? What must happen to the concentration of bicarbonate?

: CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-

Carbon dioxide concentration will increase as the reaction is shifted to the left. Bicarbonate concentration will decrease.

Section Title: Gas Transport in the Blood

Learning Outcome: 18.11

: Level III: Problem Solving (Bloom's Taxonomy: Application)

79) A chemistry student accidentally spills chlorine bleach into a dilute acid. The mixture reacts and produces fumes that are inhaled by the student and that reduce his ventilation. Assume that the gaseous chemical produced is a base (i.e., it releases OH- in an aqueous solution), and that the chemical is absorbed into the bloodstream at the alveoli. Explain why ventilation is reduced in the patient.

: The physiological response is opposite that for acidosis. A decreased ventilation would reduce loss of CO2. By maintaining higher PCO2 in the blood, the resulting acidity would help to counteract the alkalinity resulting from the inhalation of a base.

Section Title: Gas Transport in the Blood

Learning Outcome: 18.13

: Level III: Problem Solving (Bloom's Taxonomy: Application)

80) You are a scientist who has been hired to write a screenplay for a popular TV series. The plot involves the discovery by a rogue botanist of a plant toxin that interferes with the function of the exchange pump responsible for the chloride shift. This scientist provides the toxin to bioterrorists. What should you write for the coroner to say about symptoms in the poisoning victims?

: The chloride shift is the transport process that occurs in red blood cells and is necessary for normal carbon dioxide transport. In this process, a bicarbonate ion is exchanged for a chloride ion. As a result, the red blood cell loses bicarbonate, which carries a negative charge, but gains a chloride ion, thus maintaining its membrane potential. Losing the bicarbonate prevents the chemical reaction that produces bicarbonate from carbon dioxide and water from reaching equilibrium. Bicarbonate is the most important extracellular buffer in the body. Without the transporter function, bicarbonate will build up inside the red blood cell and will not be maintained in the plasma. With a reduction in plasma bicarbonate, acidosis will result. An increase in pulmonary ventilation is triggered by acidosis and can help reverse this process, but it may be unable to compensate fully for the lack of bicarbonate buffer. Chapter 20 covers some of the physiological consequences of acidosis.

Section Title: Gas Transport in the Blood

Learning Outcome: 18.12

: Level III: Problem Solving (Bloom's Taxonomy: Synthesis)

81) Which is typically more important in regulating the respiratory system, PO2 or PCO2? Explain your answer and briefly discuss the receptors involved. Give examples of situations in which each of those factors changes enough to stimulate a reflex. How and why are these factors related to each other?

: PCO2 is the more important factor. For PCO2, there are central and peripheral receptors that respond to CO2 as well as to CO2-related pH. These receptors are very sensitive to routine changes in PCO2 and pH, such as those associated with an increase in physical activity. Peripheral chemoreceptors have been identified for O2, but these respond only to dramatic changes in PO2, such as those associated with high altitude or disease. Because CO2 is produced as a by-product of aerobic (oxygen-consuming) metabolism, an increase in CO2 is associated with a corresponding decrease in O2.

Section Title: Regulation of Ventilation

Learning Outcome: 18.15

: Level III: Problem Solving (Bloom's Taxonomy: Synthesis)

82) Timmy is a cantankerous toddler who has just threatened that he will hold his breath until Mom gives him some chocolate. His mother refuses to be manipulated and watches in amusement as Timmy stubbornly refuses to breathe. To her horror, Timmy loses consciousness and collapses onto the floor. Her cousin, who is enrolled in a course for emergency medical technical (EMT) training, is visiting, and tells her there is no need to call for an ambulance. Why did Timmy lose consciousness? Should his mother trust her instincts and call for help and begin CPR, or should she listen to her well-meaning but young and inexperienced cousin? Explain.

: Timmy loses consciousness due to hypoxia in his brain. There is no need for alarm, because the loss of consciousness indicates mainly that cerebral activity has decreased. The parts of the brain involved in respiratory control are in the brain stem. As long as Timmy was awake and determined, his cerebral signals were able to inhibit brain stem control of pulmonary ventilation. Once he loses consciousness, however, the respiratory control areas are released from inhibition and he starts breathing again. Soon normal oxygen content in the brain will be restored, and Timmy will wake up.

Section Title: Regulation of Ventilation

Learning Outcome: 18.17

: Level III: Problem Solving (Bloom's Taxonomy: Synthesis)

83) Cary deliberately hyperventilates for several minutes before diving into a swimming pool. Shortly after he enters the water and begins swimming, he blacks out and almost drowns. What caused this to happen?

: Hyperventilation causes a decrease in the alveolar PCO2, and more carbon dioxide is eliminated from the body than during normal breathing. The loss of large amounts of carbon dioxide upsets the body's normal drive for ventilation, and Cary does not feel the urge to breathe as he swims. As the exercising muscles use oxygen, a state of hypoxia develops. This results in insufficient amounts of oxygen reaching the brain, causing Cary to lose consciousness.

Section Title: Regulation of Ventilation

Learning Outcome: 18.17

: Level III: Problem Solving (Bloom's Taxonomy: Synthesis)

84) Define hyperventilation and explain what may cause it. Is the increased ventilation that occurs while exercising an example of hyperventilation? Explain your answer. How are PO2 and PCO2 affected by hyperventilation? Can breathing into a paper bag remedy hyperventilation or is this just unfounded folk medicine? Explain.

: Hyperventilation is an increase in alveolar ventilation that exceeds metabolic demand. A person can deliberately hyperventilate, or it may occur as a result of emotional stress or high altitude. Strictly speaking, the increase in ventilation during exercise is necessary to meet increased metabolism and is therefore not hyperventilation. PO2 is increased and PCO2 is decreased during hyperventilation, because more O2 is inhaled and more CO2 is exhaled; this produces abnormally low PCO2. Hyperventilation can be remedied by a paper bag treatment, because rebreathing exhaled air will increase PCO2 in the body back to normal.

Section Title: Regulation of Ventilation

Learning Outcome: 18.17

: Level III: Problem Solving (Bloom's Taxonomy: Application)

85) Oxygen consumption increases with exercise due to the fact that the contracting muscles are doing work and require ATP to produce the contractions.

A) How does the body meet the increased demand for oxygen?

B) Calculate the oxygen consumption of a runner using the following information:

Heart Rate: 130 bpm; Stroke Volume: 270 mL/beat;

Arterial oxygen content: 250 mL O2/L blood,

and Venous oxygen content: 100 O2/L blood.

: In order to meet the increased oxygen usage, more blood needs to be delivered to the working muscles. This is accomplished by increasing cardiac output and by vasodilation of blood vessels to the exercising muscles thus increasing flow and delivering more oxygen rich blood. Oxygen consumption can be calculated using the Fick equation.

Qo2 = CO × (arterial oxygen content - venous oxygen content)

However, CO must be calculated first: CO = SV × HR = 130 x 250 = 32.5 L/min

Then Qo2 = 32.5 × (0.250 - 0.100) = 4.875 L O2/min

Section Title: Gas Transport in the Blood

Learning Outcome: 18.5

: Level IV: Quantitative Problems (Bloom's Taxonomy: Synthesis)

86) The graph below shows an oxygen dissociation curve, with the normal curve in the center. What is the name of the phenomenon that shifts the curve to the right? What causes this change in oxygen dissociation? Is the shift beneficial or detrimental? Explain.

: The shift in the dissociation curve is called the Bohr effect. The decrease in pH may be due to an increase in CO2 and lactic acid during vigorous physical activity, or to metabolic acidosis. The Bohr effect is beneficial, because the unloading of oxygen from hemoglobin increases under such conditions. If the decrease in pH is due to exercise, then the skeletal muscles have an increased demand for oxygen, and thus increased unloading is desirable.

Section Title: Gas Transport in the Blood

Learning Outcome: 18.7

: Level IV: Quantitative Problems (Bloom's Taxonomy: Analysis)

87) Refer to the graph below.

A. At a PO2 of 80 mm Hg, which type of hemoglobin binds more oxygen?

B. At a PO2 of 40 mm Hg, which type of hemoglobin has released more oxygen to the cell?

C. Explain the significance of the differences in fetal and maternal hemoglobin affinity.

D. If a worm lived in low oxygen mud flats where the PO2 is 60 mm Hg, which type of hemoglobin would be better for it to have? Explain.

:

A. Fetal hemoglobin has a higher affinity for oxygen than maternal hemoglobin at that oxygen pressure.

B. Maternal hemoglobin releases oxygen more readily than fetal hemoglobin at that oxygen pressure.

C. The higher affinity of fetal hemoglobin for oxygen ensures a net transfer of oxygen from the maternal blood to the fetal blood in the placenta. While unloading from fetal hemoglobin to fetal tissues is less favorable due to the higher affinity, the high rate of oxygen consumption in fetal tissues and consequent low oxygen pressure ensures unloading will occur.

D. The fetal form of hemoglobin would be better in this situation, because it has a higher affinity for the oxygen at this pressure. Thus, the worm's blood would become more saturated, and more oxygen would then be available for the worm's cells.

Section Title: Gas Transport in the Blood

Learning Outcome: 18.9

: Level IV: Quantitative Problems (Bloom's Taxonomy: Evaluation)