Deck 13: Respiratory Physiology

Question 1

Under normal circumstances,an increase in transpulmonary pressure will result in

A)Inhalation/inspiration
B)Exhalation/expiration
C)A collapsed lung
D)All of these things
E)None of these things

Answer 1

A

Question 2

The volume of air flowing into the alveoli during inhalation/inspiration is increased when there is an increase in

A)Airway resistance
B)The pressure gradient from the atmosphere to the alveoli
C)The rate of action potential firing in the motor neurons to the inhalatory/inspiratory muscles
D)Airway resistance and the pressure gradient from the atmosphere to the alveoli
E)The pressure gradient from the atmosphere to the alveoli and the rate of action potential firing in the motor neurons to the inhalatory/inspiratory muscles

Answer 2

E

Question 3

A respiratory physiologist has measured ventilation parameters for each of three subjects: Tidal volume (TV); Respiratory rate (RR),and Anatomic dead space volume (ADSV). $$\begin{array} { | l | r | r | r | } \hline & { \text { TV } } & { \text { RR } } & { \text { ADV } } \\\hline \text { Tom: } & 200 \mathrm { ml } & 40 / \mathrm { min } & 150 \mathrm { ml } \\\hline \text { Dick: } & 500 \mathrm { ml } & 10 / \mathrm { min } & 150 \mathrm { ml } \\\hline \text { Harry: } & 1000 \mathrm { ml } & 5 / \mathrm { min } & 150 \mathrm { ml } \\\hline\end{array}$$ Which of the following statements accurately compares the alveolar ventilation in the three men?

A)Tom's is the largest; Dick's and Harry's are the same
B)Tom's is the smallest; Dick's and Harry's are the same
C)Tom's is greater than Dick's, which is greater than Harry's
D)Dick's is greater than Harry's, which is greater than Tom's
E)Harry's is greater than Dick's, which is greater than Tom's

Answer 3

Harry's is greater than Dick's, which is greater than Tom's

Question 4

Which of the following drugs,administered as an aerosol spray,would be most likely to help a victim of respiratory distress syndrome of the newborn?

A)Pulmonary surfactant
B)A beta-adrenergic agonist
C)A muscarinic agonist
D)Histamine
E)A beta-adrenergic antagonist

Question 5

Inhalation/inspiration occurs as a result of

A)An upward movement of the diaphragm
B)Movement of the ribs closer together due to contraction of the inspiratory/inhalatory intercostal muscles
C)A downward movement of the diaphragm
D)An upward movement of the diaphragm and movement of the ribs closer together due to contraction of the inspiratory/inhalatory intercostal muscles
E)Movement of the ribs closer together due to contraction of the inspiratory/inhalatory intercostal muscles and a downward movement of the diaphragm

Question 6

Lung compliance is reduced in

A)Respiratory distress syndrome of the newborn
B)Prolonged shallow breathing
C)Emphysema
D)Respiratory distress syndrome of the newborn and prolonged shallow breathing
E)All of the choices are correct

Question 7

Asthma is caused by

A)Loss of alveoli
B)Inflammation of the bronchioles
C)Elevation of intrapleural pressure to equal atmospheric pressure
D)Loss of alveoli and inflammation of the bronchioles
E)Loss of alveoli and elevation of intrapleural pressure to equal atmospheric pressure

Question 8

During an unforced exhalation/expiration,all of the following are true except

A)Alveolar pressure is greater than atmospheric pressure
B)Intrapleural pressure is greater than alveolar pressure
C)Transpulmonary pressure decreases
D)The diaphragm relaxes
E)Lung volume decreases

Question 9

In order for the lungs to function normally,the intrapleural pressure must

A)Be lower than alveolar pressure
B)Be between +5 and +10 mm Hg above atmospheric pressure
C)Alternate between being less than and greater than atmospheric pressure
D)Change as the respiratory demands of the body change
E)Be the same as atmospheric pressure

Question 10

Which of the following drugs,administered as an aerosol spray,would be most likely to help a victim of an asthmatic attack?

A)Pulmonary surfactant
B)A beta-adrenergic agonist
C)A muscarinic agonist
D)Histamine
E)A beta-adrenergic antagonist

Question 11

The pleural sac

A)Protects lungs from infection
B)Prevents collapse of the lungs
C)Contains a large volume of surfactant
D)Supports the chest wall and keeps it from collapsing into lungs
E)Both prevents collapse of the lungs and supports the chest wall and keeps it from collapsing into lungs are correct

Question 12

Which of the following statements about the response of arteriolar smooth muscle to changing oxygen partial pressures is true?

A)Both systemic and pulmonary arterioles respond to a decrease in by constricting
B)Both systemic and pulmonary arterioles respond to a decrease in $\mathrm { P } _ { \mathrm { o } _ { 2 } }$ by dilating
C)Systemic arterioles respond to a decrease in $\mathrm { P } _ { \mathrm { o } _ { 2 } }$ by dilating but pulmonary arterioles constrict in response to decreased $\mathrm { P } _ { \mathrm { o } _ { 2 } }$
D)Systemic arterioles respond to a decrease in by constricting but pulmonary arterioles dilate in response to decreased $\mathrm { P } _ { \mathrm { o } _ { 2 } }$
E)None of the choices are true

Question 13

The concentration of a gas in a liquid is

A)Directly proportional to the partial pressure of the gas in the air around the liquid
B)Directly proportional to the solubility of the gas in the liquid
C)The partial pressure of the gas in the liquid
D)Directly proportional to the partial pressure of the gas in the air around the liquid and directly proportional to the solubility of the gas in the liquid
E)All of the choices are correct

Question 14

Functions of the respiratory system include each of the following except

A)Exchange of carbon dioxide from the air with oxygen from the blood
B)Regulation of blood H⁺ concentration
C)Trapping of blood clots
D)Phonation
E)Defense against microbes

Question 15

That the lung surface and the thoracic wall will move in and out together,rather than separately,during ventilation is assured by the

A)Diaphragm
B)Inhalatory/inspiratory intercostal muscles
C)Exhalatory/expiratory intercostal muscles
D)Intrapleural fluid
E)Alveoli

Question 16

During a physical examination,Joe learns that his resting tidal volume is 500 ml; his average resting respiratory rate is 12 breaths per minute; his total lung capacity is 6000 ml; and his anatomic dead space is 150 ml.Joe's resting alveolar ventilation is

A)72.0 L/min
B)6.0 L/min
C)4.2 L/min
D)1.8 L/min
E)0.5 L/min

Question 17

In an average-size subject with a resting breathing rate of 10 breaths per minute at sea level,what is the approximate alveolar O2 ventilation in liters?

A)5.0
B)3.5
C)1.5
D)0.7
E)0.2

Question 18

Which of the following statements regarding pulmonary surfactant is true?

A)It is secreted by type I alveolar cells
B)It increases the compliance of the lungs
C)It decreases airway resistance
D)Both it is secreted by type I alveolar cells and it increases the compliance of the lungs are true
E)Both it increases the compliance of the lungs and it decreases airway resistance are true

Question 19

The type II alveolar cells are important because they

A)Produce surfactant
B)Secrete mucus
C)Phagocytize bacteria and other foreign particles
D)Do all of these things
E)Do none of these things

Question 20

The bronchi and bronchioles

A)Are part of the anatomic dead space
B)Increase surface area for gas exchange
C)Account for the total dead space in the lungs
D)Both are part of the anatomic dead space and increase surface area for gas exchange are correct
E)Both increase surface area for gas exchange and account for the total dead space in the lungs are correct

Question 21

Regarding the relationships between the rates of oxygen consumption/carbon dioxide production and alveolar ventilation,

A)Increased ventilation without a similar increase in oxygen consumption is called hyperventilation
B)In hypoventilation, alveolar $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ increases above resting levels
C)In hyperventilation, alveolar $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ can fall to zero
D)Both increased ventilation without a similar increase in oxygen consumption is called hyperventilation and in hypoventilation, alveolar $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ increases above resting levels are correct
E)Both in hypoventilation, alveolar $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ increases above resting levels and in hyperventilation, alveolar can fall to zero are correct

Question 22

Hyperventilation

A)Results in respiratory alkalosis
B)Results in respiratory acidosis
C)Lowers blood $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$
D)Both results in respiratory alkalosis and lowers blood $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ are correct
E)Both results in respiratory acidosis and lowers blood $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ are correct

Question 23

The affinity of hemoglobin for oxygen is decreased by

A)Decreased H+ ion concentration
B)Decreased pCO2
C)Increased temperature
D)Decreased diphosphoglycerate concentration
E)Both decreased H+ ion concentration and decreased pCO2

Question 24

Which of the following statements regarding the transport of CO2 in blood is true?

A)Some of the CO2 in blood is dissolved in plasma
B)Some of the CO2 in blood is dissolved in the cytosol of erythrocytes
C)Some of the CO2 in blood is bound to hemoglobin
D)Most of the CO2 in blood is converted to another molecule
E)All of the these statements are true

Question 25

Hyperventilation results in

A)Increased alveolar $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ and decreased alveolar $\mathrm { P } _ { \mathrm { o } _ { 2 } }$
B)Increased alveolar $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ and $\mathrm { P } _ { \mathrm { o } _ { 2 } }$
C)Decreased alveolar $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ and increased alveolar $\mathrm { P } _ { \mathrm { o } _ { 2 } }$
D)Decreased alveolar $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ and $\mathrm { P } _ { \mathrm { o } _ { 2 } }$
E)No change in alveolar $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ gas concentrations

Question 26

Chemoreceptors include

A)Hair cells in the cochlea
B)Receptors in the aortic and carotid bodies
C)Baroreceptors in the aortic and carotid arch
D)Hair cells in the cochlea and receptors in the aortic and carotid bodies
E)Receptors in the aortic and carotid bodies and baroreceptors in the aortic and carotid arch

Question 27

The hypothesized value in hemoglobin's ability to bind and transport nitric oxide is

A)It allows hemoglobin to resist the effects of small pH changes as buffer molecule
B)By circulation into peripheral vessels it will trigger vasodilation to improve local blood flow
C)As it circulates it promotes smooth muscle of arteries and arterioles to contract, to increase blood pressure as needed
D)It acts as an enzyme cofactor necessary to maintaining a "clean and smooth" endothelial lining within blood vessels
E)It provides a mechanism upon which additional electrolytes can be transported to deficient tissues in the body

Question 28

Oxygen is carried in blood

A)Bound to hemoglobin
B)Dissolved in the plasma
C)Dissolved in the cytosol of erythrocytes
D)Both bound to hemoglobin and dissolved in the cytosol of erythrocytes are correct
E)All of the choices are correct

Question 29

The skeletal muscles involved in producing the contractions related to inspiration are stimulated by motor impulses originating from

A)The ventral respiratory group of the medulla oblongata
B)The Pre-Botzinger complex
C)The dorsal respiratory group of the medulla oblongata
D)Pneumotaxic center of the pons
E)Apneustic center of the pons

Question 30

During hypoventilation

A)A person's rate and depth of ventilation is dramatically increased
B)The person's levels of blood CO2 increase
C)The person's levels of blood H+ ions increase; blood pH decreases
D)Both a person's rate and depth of ventilation is dramatically increased and the person's levels of blood H+ ions increase; blood pH decreases are correct
E)Both the person's levels of blood CO2 increase and the person's levels of blood H+ ions increase; blood pH decreases are correct

Question 31

Action potentials in neurons in the inhalatory/inspiratory center of the medulla result in action potentials in the ________ nerves to the diaphragm,which in turn cause ________ of the muscle,resulting in a/an ________ in the volume of the thoracic cage.

A)Motor; contraction; decrease
B)Parasympathetic; contraction; decrease
C)Sympathetic; contraction; increase
D)Motor; contraction; increase
E)Sympathetic; relaxation; increase

Question 32

An increase in arterial H+ concentration is detected by

A)The medulla, which acts to increase respiratory rate
B)The peripheral chemoreceptors
C)The central chemoreceptors
D)The diaphragm, which increases breathing rate
E)The peripheral chemoreceptors and the central chemoreceptors

Question 33

Which of the following would cause a decrease in the binding affinity of hemoglobin for oxygen?

A)Increased pH of the blood
B)Increased temperature of the blood
C)Decreased DPG levels in erythrocytes
D)Both increased pH of the blood and increased temperature of the blood are correct
E)Both increased temperature of the blood and decreased DPG levels in erythrocytes are correct

Question 34

Which of the following is not true regarding ventilation-perfusion inequality?

A)It does not exist in normal lungs
B)It may result from increased alveolar dead space
C)It is increased in emphysema
D)It is caused by too little or too much blood flow relative to ventilation
E)It is caused by too little or too much ventilation relative to blood flow

Question 35

Regarding the partial pressures of O₂ and CO₂,which of the following statements is not true in a normal person at rest?

A)Atmospheric $\mathrm { P } _ { \mathrm { o } _ { 2 } }$ is greater than alveolar $\mathrm { P } _ { \mathrm { o } _ { 2 } }$
B) $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ In air is less than alveolar $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$
C)Alveolar $\mathrm { P } _ { \mathrm { o } _ { 2 } }$ is greater than the $\mathrm { P } _ { \mathrm { o } _ { 2 } }$ in the pulmonary capillaries
D) $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ In the systemic veins exceeds systemic arterial $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$
E) $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ In the systemic arteries exceeds systemic venous $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$

Question 36

According to the oxygen-hemoglobin dissociation curve,

A)The greater the $\mathrm { P } _ { \mathrm { o } _ { 2 } }$ of the blood, the greater the dissociation of O2 from hemoglobin
B)At normal systemic arterial $\mathrm { P } _ { \mathrm { o } _ { 2 } }$ , hemoglobin is almost 100% saturated
C)At normal systemic venous $\mathrm { P } _ { \mathrm { o } _ { 2 } }$ , only about 25% of the hemoglobin is in the form of deoxyhemoglobin
D)Both the greater the $\mathrm { P } _ { \mathrm { o } _ { 2 } }$ of the blood, the greater the dissociation of O2 from hemoglobin and at normal systemic arterial $\mathrm { P } _ { \mathrm { o } _ { 2 } }$ , hemoglobin is almost 100% saturated are correct
E)Both at normal systemic arterial $\mathrm { P } _ { \mathrm { o } _ { 2 } }$ , hemoglobin is almost 100% saturated and at normal systemic venous $\mathrm { P } _ { \mathrm { o } _ { 2 } }$ , only about 25% of the hemoglobin is in the form of deoxyhemoglobin are correct

Question 37

Carbonic anhydrase catalyzes the chemical combination of

A)H2O and O2
B)H2O and CO2
C)H2O and CO
D)H+ and HCO3-
E)None of these choices

Question 38

Curve B below represents the oxygen-hemoglobin dissociation curve for normal body temperature,arterial hydrogen ion concentration,and DPG concentration. $\mathrm { P } _ { \mathrm { o } _ { 2 } }$ (mm Hg)

A)Curve A may represent the dissociation at higher than normal arterial hydrogen ion concentration
B)Curve C may represent the dissociation at lower than normal body temperature
C)Curve A may represent the dissociation at very low DPG levels
D)Both curve A may represent the dissociation at higher than normal arterial hydrogen ion concentration and curve C may represent the dissociation at lower than normal body temperature are correct
E)Both curve A may represent the dissociation at higher than normal arterial hydrogen ion concentration and curve A may represent the dissociation at very low DPG levels are correct

Question 39

Most of the CO2 that is transported in blood is

A)Dissolved in the plasma
B)Bound to hemoglobin
C)In carbonic acid
D)In bicarbonate ion
E)In carbonic anhydrase

Question 40

Hemoglobin

A)Has a higher affinity for H+ when in the deoxy state
B)Increases the oxygen-carrying capacity of blood
C)Has a higher affinity for oxygen during exercise due to increased temperature and decreased pH
D)Both has a higher affinity for H+ when in the deoxy state and increases the oxygen-carrying capacity of blood are correct
E)Both increases the oxygen-carrying capacity of blood and has a higher affinity for oxygen during exercise due to increased temperature and decreased pH are correct

Question 41

Which of the following statements regarding control of respiration is correct?

A)A slight decrease in arterial $P _ { o _ { 2 } }$ ) is a stronger stimulus for increased ventilation than is a comparable decrease in arterial $P _ { o _ { 2 } }$
B)The most important signal for regulating ventilation is the H ion concentration of arterial blood
C)Increased concentrations of lactic acid stimulate ventilation primarily by acting on peripheral chemoreceptors
D)All of the choices are correct
E)None of the choices are correct

Question 42

According to Boyle's law,the pressure exerted by a constant number of gas molecules in a container is inversely proportional to the volume of the container.Therefore,increasing the volume of the container will cause a decrease in its pressure.

Question 43

The diaphragm is a large sheet of smooth muscle that separates the thorax from the abdomen.

Question 44

Compared to healthy people who live at sea level,arterial $P _ { o _ { 2 } }$ is lower in people who

A)Live at high altitude
B)Have pulmonary edema
C)Have iron-deficiency anemia
D)Both live at high altitude and have pulmonary edema are correct
E)All of the choices are correct

Question 45

During inhalation/inspiration,the diaphragm contracts and the alveolar pressure is less than atmospheric pressure; during exhalation/expiration,the diaphragm relaxes and the alveolar pressure is greater than atmospheric pressure.

Question 46

Stimuli or conditions that would tend to increase ventilation include

A)Lower than normal blood $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$
B)Higher than normal blood pH
C)Breathing carbon monoxide
D)Iron-deficiency anemia
E)Breathing air with reduced $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$

Question 47

During inhalation/inspiration,the total alveolar volume decreases.

Question 48

Infants born prematurely frequently develop respiratory distress syndrome of the newborn because they have too few alveoli to exchange O₂ and CO₂ efficiently.

Question 49

During heavy exercise,all of the following increase except

A)Minute ventilation
B)Arterial $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$
C)Oxygen delivery to muscles
D)Oxygen extraction by muscles
E)Body heat production

Question 50

Following strenuous exercise,blood levels of lactic acid are ________ compared to pre-exercise levels.This change in acid concentration causes a reflex ________ in ventilation by activating ________.

A)Decreased; decrease; peripheral chemoreceptors
B)Decreased; decrease; central chemoreceptors
C)Increased; increase; baroreceptors in the aortic arch
D)Increased; increase; central chemoreceptors
E)Increased; increase; peripheral chemoreceptors

Question 51

In a normal person at rest,the part of the respiratory cycle in which no air is flowing through the airways and the respiratory muscles are relaxed is at the end of inhalation/inspiration,prior to exhalation/expiration.

Question 52

If the parietal pleura is cut during surgery,the lung on the side of the cut will expand and the chest wall will be compressed.

Question 53

Compared to normal people,people suffering from hypoxic hypoxia will have

A)Elevated plasma concentration of erythropoietin
B)A higher hematocrit
C)Higher arterial $P _ { o _ { 2 } }$ values
D)Elevated plasma concentration of erythropoietin and a higher hematocrit
E)All of the choices are correct

Question 54

Which of the following statements regarding hypoxia is correct?

A)Exposure to high altitude is a form of hypoxic hypoxia
B)"Anemic hypoxia" refers to the condition of lower than normal arterial $P _ { o _ { 2 } }$
C)Carbon monoxide poisoning is an example of anemic hypoxia
D)Both exposure to high altitude is a form of hypoxic hypoxia and "anemic hypoxia" refers to the condition of lower than normal arterial $P _ { o _ { 2 } }$ are correct
E)Both exposure to high altitude is a form of hypoxic hypoxia and carbon monoxide poisoning is an example of anemic hypoxia are correct

Question 55

Exhalation/expiration of air from the lungs requires contraction of the exhalatory/expiratory intercostal muscles.

Question 56

The primary regulator of the magnitude of ventilation under normal circumstances is

A)The H⁺ concentration in the brain extracellular fluid, which is monitored by central chemoreceptors
B)The $P _ { o _ { 2 } }$ of the arterial blood, which is monitored by central chemoreceptors
C)The $P _ { o _ { 2 } }$ of the arterial blood, which is monitored by peripheral chemoreceptors
D)The H+ concentration in the arterial blood, which is monitored by central chemoreceptors

Question 57

If the nerves from the carotid and aortic bodies are cut,

A)A decrease in arterial $P _ { o _ { 2 } }$ will no longer stimulate increased ventilation
B)An increase in arterial $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ will no longer stimulate increased ventilation
C)An increase in arterial lactic acid will no longer stimulate increased ventilation
D)Both a decrease in arterial $P _ { o _ { 2 } }$ will no longer stimulate increased ventilation and an increase in arterial $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ will no longer stimulate increased ventilation will occur
E)Both a decrease in arterial $P _ { o _ { 2 } }$ will no longer stimulate increased ventilation and an increase in arterial lactic acid will no longer stimulate increased ventilation will occur

Question 58

The diameter of the airways in normal lungs is generally great enough that little resistance is offered to airflow.

Question 59

The process of ventilation includes both the transport of gases by bulk flow and the diffusion of gases into and out of the blood.

Question 60

A person who travels from sea level to a high elevation will initially experience bouts of increased ventilation followed by periods of suppressed ventilation.After a day or two,ventilation will be increased without suppression.The best explanation for the initial events is

A)Arteriolar $P _ { o _ { 2 } }$ is decreased, which initiates reflexes leading to increased ventilation.Increased ventilation causes an increase in blood $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ , which initiates reflexes leading to decreased ventilation
B)Arteriolar $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ is decreased, which initiates reflexes leading to increased ventilation.Increased ventilation causes an increase in blood $P _ { o _ { 2 } }$ , which initiates reflexes leading to decreased ventilation
C)Arteriolar $P _ { o _ { 2 } }$ is decreased, which initiates reflexes leading to increased ventilation.Increased ventilation causes a decrease in blood $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ , which initiates reflexes leading to decreased ventilation
D)Arteriolar $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ is increased, which initiates reflexes leading to increased ventilation.Increased ventilation causes an increase in blood $P _ { o _ { 2 } }$ which initiates reflexes leading to decreased ventilation
E)Arteriolar $P _ { o _ { 2 } }$ is increased, which initiates reflexes leading to increased ventilation.Increased ventilation causes a decrease in blood $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ , which initiates reflexes leading to decreased ventilation

Question 61

The total dead space in the lungs includes anatomic dead space and any portion of the alveoli that has little or no blood supply.

Question 62

Deoxyhemoglobin binds bicarbonate ion better than oxyhemoglobin does.

Question 63

Most of the O2 carried in the blood is dissolved in plasma.

Question 64

In the systemic circulation,the $P _ { o _ { 2 } }$ of arterial blood exceeds the $P _ { o _ { 2 } }$ of venous blood,while the reverse is true for the pulmonary circulation.

Question 65

Emphysema is a disease characterized by low lung compliance,obstructed airways,and ventilation-perfusion inequality.

Question 66

The rhythmic contractions and relaxations of the inhalatory/inspiratory muscles are dependent upon spontaneous depolarizations of the diaphragm.

Question 67

Normally all the H⁺ ions generated in tissue capillaries recombine with bicarbonate,then go to forming CO₂ and water in pulmonary capillaries and don't appear in arterial blood.

Question 68

If a tissue increases its metabolism enough to drop its interstitial $P _ { o _ { 2 } }$ to half the resting venous value,the amount of O₂ available from oxyhemoglobin will be more than twice that for the resting tissue.

Question 69

The medullary inhalatory/inspiratory neurons receive inhibitory neural input from the pons and also from pulmonary stretch receptors.

Question 70

The neurons responsible for the cyclic nature of respiratory-muscle function are located in the brain stem.

Question 71

At sea level $P _ { o _ { 2 } }$ ,is about 760 mm Hg.

Question 72

If lung disease results in an arterial $P _ { o _ { 2 } }$ of 80 mm Hg,the ability of the blood to carry O₂ to the tissues is severely compromised.

Question 73

In the systemic capillaries,the $P _ { o _ { 2 } }$ of the erythrocytes is greater than the $P _ { o _ { 2 } }$ of the plasma,causing a shift from oxyhemoglobin to deoxyhemoglobin.

Question 74

Doubling the rate of breathing will cause a greater increase in alveolar ventilation than will doubling the depth of inspiration.

Question 75

Decreased alveolar $P _ { o _ { 2 } }$ causes reflex vasodilation of the pulmonary arterioles.

Question 76

The affinity of hemoglobin for O₂ is decreased in rapidly metabolizing tissues.

Question 77

A clinical sign of obstructive lung disease would be a reduced FEV1/FVC ratio.

Question 78

The majority of hydrogen ions generated in the formation of carbonic acid are carried dissolved in the plasma.

Question 79

Unlike O₂,more of the CO₂ in blood is dissolved in plasma than is bound to hemoglobin.

Question 80

When a person hyperventilates,there are lower than normal levels of $\mathrm { P } _ { \mathrm { CO } _ { 2 } }$ and hydrogen ion in arterial blood,a condition called respiratory alkalosis.