Chapter 13 The Respiratory System

Question 1

Respiratory Anatomy

• Cellular respiration refers to the _______ metabolic reactions that use O₂ and produce CO₂ during energy-yielding oxidation of nutrient molecules.
• _______ respiration refers to the transfer of O₂ and CO₂ between the external environment and tissue cells.
• The respiratory and _______ systems function together to accomplish external respiration.

Answer 1

Respiratory Anatomy

• Cellular respiration refers to the intracellular metabolic reactions that use O₂ and produce CO₂ during energy-yielding oxidation of nutrient molecules.
• External respiration refers to the transfer of O₂ and CO₂ between the external environment and tissue cells.
• The respiratory and circulatory systems function together to accomplish external respiration.

Question 2

Respiratory Anatomy

• The respiratory system exchanges air between the _____ and _____ .
• The airways conduct air from the atmosphere to the _____ , across which O2 and CO2 are exchanged between air in these air sacs and blood in the surrounding __________ .
• The extremely thin alveolar walls are formed by __________ .
• _____ alveolar cells secrete __________ .

Answer 2

Respiratory Anatomy

• The respiratory system exchanges air between the atmosphere and lungs.
• The airways conduct air from the atmosphere to the alveoli, across which O2 and CO2 are exchanged between air in these air sacs and blood in the surrounding pulmonary capillaries.
• The extremely thin alveolar walls are formed by Type I alveolar cells.
• Type II alveolar cells secrete pulmonary surfactant.

Question 3

Respiratory Anatomy

• The lungs consist of the smaller airways, _______, _______ arteries, and highly elastic _______.
• They are housed within the closed compartment of the _______, the volume of which can be changed by _______ of surrounding respiratory muscles.
• Each lung is surrounded by a double-walled, closed _______.

Answer 3

Respiratory Anatomy

• The lungs consist of the smaller airways, alveoli, pulmonary arteries, and highly elastic connective tissue.
• They are housed within the closed compartment of the thorax, the volume of which can be changed by contractile activity of surrounding respiratory muscles.
• Each lung is surrounded by a double-walled, closed pleural sac.

Question 4

Respiratory Mechanics

• Ventilation, or breathing, is the process of ____ moving air in and out of the lungs so that old alveolar air that has given up ____ and picked up ____ can be exchanged for fresh air.

Answer 4

Respiratory Mechanics

• Ventilation, or breathing, is the process of cyclically moving air in and out of the lungs so that old alveolar air that has given up O2 and picked up CO2 can be exchanged for fresh air.

Question 5

Respiratory Mechanics

• Ventilation is mechanically accomplished by alternately shifting the direction of the __________ for air flow between the atmosphere and _____ through the cyclic expansion and recoil of the lungs.
• When intra-alveolar pressure _____ as a result of lung expansion during inspiration, air flows into the lungs from the higher atmospheric pressure.
• When intra-alveolar pressure _____ as a result of lung recoil during expiration, air flows out of the lungs toward the lower atmospheric pressure.

Answer 5

Respiratory Mechanics

• Ventilation is mechanically accomplished by alternately shifting the direction of the pressure gradient for air flow between the atmosphere and alveoli through the cyclic expansion and recoil of the lungs.
• When intra-alveolar pressure decreases as a result of lung expansion during inspiration, air flows into the lungs from the higher atmospheric pressure.
• When intra-alveolar pressure increases as a result of lung recoil during expiration, air flows out of the lungs toward the lower atmospheric pressure.

Question 6

Respiratory Mechanics

• Alternate contraction and relaxation of the ____ muscles (primarily the ____) indirectly produce periodic inflation and deflation of the lungs by cyclically expanding and com- pressing the ________, with the lungs passively following its movements.

Answer 6

Respiratory Mechanics

• Alternate contraction and relaxation of the inspiratory muscles (primarily the diaphragm) indirectly produce periodic inflation and deflation of the lungs by cyclically expanding and com- pressing the thoracic cavity, with the lungs passively following its movements.

Question 7

Respiratory Mechanics

• The lungs follow the movements of the thoracic cavity by virtue of the __________ _____ across the lung wall resulting from the intrapleural pressure being _______ and thus less than the intra-alveolar pressure.

Answer 7

Respiratory Mechanics

• The lungs follow the movements of the thoracic cavity by virtue of the transmural pressure gradient across the lung wall resulting from the intrapleural pressure being subatmospheric and thus less than the intra-alveolar pressure.

Question 8

Respiratory Mechanics

• Because energy is ______ for contracting the inspiratory muscles, inspiration is an ______ process, but expiration is ______ during quiet breathing because it is accomplished by ____________ of the lungs when the inspiratory muscles relax, at no ______ expense.

Answer 8

Respiratory Mechanics

• Because energy is required for contracting the inspiratory muscles, inspiration is an active process, but expiration is passive during quiet breathing because it is accomplished by elastic recoil of the lungs when the inspiratory muscles relax, at no energy expense.

Question 9

Respiratory Mechanics

• For more forceful active expiration, contraction of the ______ muscles (namely, the ____________) further decreases the size of the ____________ and ______, which further increases the intra-alveolar–to–atmospheric-pressure gradient.

Answer 9

Respiratory Mechanics

• For more forceful active expiration, contraction of the expiratory muscles (namely, the abdominal muscles) further decreases the size of the thoracic cavity and lungs, which further increases the intra-alveolar–to–atmospheric-pressure gradient.

Question 10

Respiratory Mechanics

• The larger the pressure gradient between the alveoli and atmosphere in either direction, the larger the ______ because air flows until intra-alveolar pressure ______ with atmospheric pressure.

Answer 10

Respiratory Mechanics

• The larger the pressure gradient between the alveoli and atmosphere in either direction, the larger the air flow rate because air flows until intra-alveolar pressure equilibrates with atmo- spheric pressure.

Question 11

Respiratory Mechanics

• Besides being directly proportional to the pressure gradient, air flow rate is also inversely proportional to __________.
• Because airway resistance, which depends on the caliber of the __________, is normally very _____, air flow rate usually depends primarily on the pressure gradient between the _____ and atmosphere.

Answer 11

Respiratory Mechanics

• Besides being directly proportional to the pressure gradient, air flow rate is also inversely proportional to airway resistance.
• Because airway resistance, which depends on the caliber of the conducting airways, is normally very low, air flow rate usually depends primarily on the pressure gradient between the alveoli and atmosphere.

Question 12

Respiratory Mechanics

• The lungs can be stretched to varying degrees during inspiration and then recoil to their preinspiratory size during expiration because of their ______ behavior.
• Pulmonary compliance refers to the ______ of the lungs—how much they stretch in response to a given change in the __________________.
• ___________ refers to the snapping back of the lungs to their resting position during expiration.

Answer 12

Respiratory Mechanics

• The lungs can be stretched to varying degrees during inspiration and then recoil to their preinspiratory size during expiration because of their elastic behavior.
• Pulmonary compliance refers to the distensibility of the lungs—how much they stretch in response to a given change in the transmural pressure gradient.
• Elastic recoil refers to the snapping back of the lungs to their resting position during expiration.

Question 13

Respiratory Mechanics

• Pulmonary elastic behavior depends on the ____________ in the lung and on alveolar ____________.
• Alveolar surface tension, which is the result of attractive forces between the ____________ lining each alveolus, tends to resist the alveolus being stretched on inflation (______ compliance) and tends to return it back to a smaller surface area during deflation (______ lung rebound).

Answer 13

Respiratory Mechanics

• Pulmonary elastic behavior depends on the elastin fibers in the lung and on alveolar surface tension.
• Alveolar surface tension, which is the result of attractive forces between the surface water molecules lining each alveolus, tends to resist the alveolus being stretched on inflation (decreases compliance) and tends to return it back to a smaller surface area during deflation (increases lung rebound).

Question 14

Respiratory Mechanics

• If the alveoli were lined by water alone, the ________ would be so great that the lungs would be poorly compliant and would tend to ________.
• ________________intersperses between the water molecules and lowers alveolar surface tension, thereby increasing ________ and counteracting the tendency for alveoli to ________.

Answer 14

Respiratory Mechanics

• If the alveoli were lined by water alone, the surface tension would be so great that the lungs would be poorly compliant and would tend to collapse.
• Pulmonary surfactant intersperses between the water molecules and lowers alveolar surface tension, thereby increasing compliance and counteracting the tendency for alveoli to collapse.

Question 15

Respiratory Mechanics

• The lungs can be fillled to about 5.5 liters on maximal _____ or emptied to about 1 liter on maximal _____.
• Normally the lungs operate at “half full.” Lung volume typically varies from about 2 to 2.5 liters as an _______________ of 500 mL of air is moved in and out with each breath.

Answer 15

Respiratory Mechanics

• The lungs can be filled to about 5.5 liters on maximal inspiration or emptied to about 1 liter on maximal expiration.
• Normally the lungs operate at “half full.” Lung volume typically varies from about 2 to 2.5 liters as an average tidal volume of 500 mL of air is moved in and out with each breath.

Question 16

Respiratory Mechanics

• The amount of air moved in and out of the lungs in one minute, the ______ ventilation, is equal to tidal volume times ____________.
• Not all the air moved in and out is available for gas exchange with the blood because __________________ (anatomic dead space).
• ______ ventilation, the volume of air exchanged between the atmosphere and alveoli in one minute, is a measure of the air actually available for ____________ with the blood.
• ______ ventilation equals (tidal volume minus dead space volume) times respiratory rate.

Answer 16

Respiratory Mechanics

• The amount of air moved in and out of the lungs in one minute, the pulmonary ventilation, is equal to tidal volume times respiratory rate.
• Not all the air moved in and out is available for gas exchange with the blood because part occupies the conducting airways (anatomic dead space).
• Alveolar ventilation, the volume of air exchanged between the atmosphere and alveoli in one minute, is a measure of the air actually available for gas exchange with the blood.
• Alveolar ventilation equals (tidal volume minus dead space volume) times respiratory rate.

Question 17

Respiratory Mechanics

• Even though ventilation and perfusion rates are both higher at the ____ than at the ____ of the lungs (with the ventilation–perfusion ratio being ____ at the top), ____ controls act on bronchiolar and pulmonary arteriolar ________ to match air flow and blood flow to each area of the lung as much as possible.

Answer 17

Respiratory Mechanics

• Even though ventilation and perfusion rates are both higher at the bottom than at the top of the lungs (with the ventilation–perfusion ratio being higher at the top), local controls act on bronchiolar and pulmonary arteriolar smooth muscle to match air flow and blood flow to each area of the lung as much as possible.

Question 18

Gas Exchange

• O2 and CO2 move across body membranes by ____________ down partial pressure gradients.
• The partial pressure of a gas in air is that portion of the ______ atmospheric pressure contributed by this ______ gas, which in turn is directly proportional to the percentage of this gas in the air.
• The partial pressure of a gas in blood depends on the amount of this gas ____________.

Answer 18

Gas Exchange

• O2 and CO2 move across body membranes by passive diffusion down partial pressure gradients.
• The partial pressure of a gas in air is that portion of the total atmospheric pressure contributed by this individual gas, which in turn is directly proportional to the percentage of this gas in the air.
• The partial pressure of a gas in blood depends on the amount of this gas dissolved in the blood.

Question 19

Gas Exchange

• Net diffusion of O2 occurs first between the ____ and blood and then between the blood and ____ as a result of the ____________ created by continuous use of O2 in the cells and continuous replenishment of fresh alveolar O2 provided by ventilation.
• Net diffusion of CO2 occurs first between the ____ and blood and then between the blood and ____, as a result of the ______________ created by continuous production of CO2 in the cells and continuous removal of alveolar CO2 through ventilation.

Answer 19

Gas Exchange

• Net diffusion of O2 occurs first between the alveoli and blood and then between the blood and tissues as a result of the O2 partial pressure gradients created by continuous use of O2 in the cells and continuous replenishment of fresh alveolar O2 provided by ventilation.
• Net diffusion of CO2 occurs first between the tissues and blood and then between the blood and alveoli, as a result of the CO2 partial pressure gradients created by continuous production of CO2 in the cells and continuous removal of alveolar CO2 through ventilation.

Question 20

Gas Exchange

• Other factors that influence the rate of gas exchange are ________ and ____ of the ____ across which the gas is diffusing and the diffusion constant of the gas in the membrane (____ law of diffusion).

Answer 20

Gas Exchange

• Other factors that influence the rate of gas exchange are surface area and thickness of the membrane across which the gas is diffusing and the diffusion constant of the gas in the membrane (Fick’s law of diffusion).

Question 21

Gas Transport

• Because O2 and CO2 are ________ in blood, they must be transported primarily by mechanisms other than ________________.
• Only 1.5% of the O2 is physically dissolved in the blood, with 98.5% chemically bound to ________.

Answer 21

Gas Transport

• Because O2 and CO2 are not that soluble in blood, they must be transported primarily by mechanisms other than simply being physically dissolved.
• Only 1.5% of the O2 is physically dissolved in the blood, with 98.5% chemically bound to hemoglobin (Hb).

Question 22

Gas Transport

• The primary factor that determines the extent to which Hb and O2 are combined (the % Hb saturation) is the ___ of the blood, depicted by an S-shaped curve known as the O2–Hb dissociation curve.
• In the PO2 range of the ____________ (the plateau portion of the curve), Hb is still almost fully saturated even if the blood PO2 falls as much as 40%.
• This provides a margin of safety by ensuring near-normal O2 delivery to the tissues despite a substantial reduction in ______.
• In the PO2 range in the ___ capillaries (the steep portion of the curve), Hb unloading increases greatly in response to a _________ in blood PO2 associated with increased ________.
• In this way, more O2 is provided to match the increased tissue ______.

Answer 22

Gas Transport

• The primary factor that determines the extent to which Hb and O2 are combined (the % Hb saturation) is the PO2 of the blood, depicted by an S-shaped curve known as the O2–Hb dissociation curve.
• In the PO2 range of the pulmonary capillaries (the plateau portion of the curve), Hb is still almost fully saturated even if the blood PO2 falls as much as 40%.
• This provides a margin of safety by ensuring near-normal O2 delivery to the tissues despite a substantial reduction in arterial PO2.
• In the PO2 range in the systemic capillaries (the steep portion of the curve), Hb unloading increases greatly in response to a small local decline in blood PO2 associated with increased cellular metabolism.
• In this way, more O2 is provided to match the increased tissue needs.

Question 23

Gas Transport

• Increased P_CO2, increased acid, and increased temperature at the tissue level shift the O2–Hb curve to the ___, facilitating the ______ of O2 from Hb for tissue use.

Answer 23

Gas Transport

• Increased P_CO2, increased acid, and increased temperature at the tissue level shift the O2–Hb curve to the right, facilitating the unloading of O2 from Hb for tissue use.

Question 24

Gas Transport

• Hemoglobin facilitates a large net transfer of O2 between ____ and blood and between blood and ________ by acting as a storage depot to keep PO2 (that is, dissolved O2 concentration) ____, despite a considerable increase in the total _______ of the blood.

Answer 24

Gas Transport

• Hemoglobin facilitates a large net transfer of O2 between alveoli and blood and between blood and tissue cells by acting as a storage depot to keep PO2 (that is, dissolved O2 concentration) low, despite a considerable increase in the total O2 content of the blood.

Question 25

Gas Transport

• CO₂ picked up at the ______ capillaries is transported in blood by three means:
  
  1. 10% is __________________
  2. 30% is ____________
  3. 60% __________________.
• The erythrocyte enzyme ______________ catalyzes conversion of CO₂ to HCO₃^– according to the reaction:
  
  • CO₂ + H₂O -> H⁺ + HCO₃^–.
• These reactions are all ______ in the lungs as CO₂ is eliminated to the ______.

Answer 25

Gas Transport

• CO₂ picked up at the systemic capillaries is transported in blood by three means:
  
  1. 10% is physically dissolved
  2. 30% is bound to Hb
  3. 60% takes the form of bicarbonate (HCO₃^-).
• The erythrocyte enzyme carbonic anhydrase catalyzes conversion of CO₂ to HCO₃^– according to the reaction CO₂ + H₂O -> H⁺ + HCO₃^–.
• These reactions are all reversed in the lungs as CO₂ is eliminated to the alveoli.

Question 26

Control of Respiration

• Ventilation involves two aspects, both subject to ____ control:
  
  1. ________ between inspiration and expiration
  2. regulation of ventilation ____, which depends on control of ____ and depth of ________.

Answer 26

Control of Respiration

• Ventilation involves two aspects, both subject to neural control:
  
  1. rhythmic cycling between inspiration and expiration
  2. regulation of ventilation magnitude, which depends on control of respiratory rate and depth of tidal volume.

Question 27

Control of Respiration

• Respiratory rhythm is established by the _______, which displays _______ activity and drives the inspiratory neurons located in the dorsal respiratory group (DRG) of the_____________________.
• When these neurons fire, impulses ultimately reach the ______________ to bring about inspiration.

Answer 27

Control of Respiration

• Respiratory rhythm is established by the pre-Bötzinger complex, which displays pacemaker activity and drives the inspiratory neurons located in the dorsal respiratory group (DRG) of the medullary respiratory control center.
• When these neurons fire, impulses ultimately reach the inspiratory muscles to bring about inspiration.

Question 28

Control of Respiration

• When the inspiratory neurons stop firing, the inspiratory muscles ___ and ___ expiration takes place.
• For active expiration, the ______ muscles are activated at this time by expiratory neurons in the _______________ of the medullary respiratory control center.

Answer 28

Control of Respiration

• When the inspiratory neurons stop firing, the inspiratory muscles relax and passive expiration takes place.
• For active expiration, the expiratory muscles are activated at this time by expiratory neurons in the ventral respiratory group (VRG) of the medullary respiratory control center.

Question 29

Control of Respiration

• This basic rhythm is smoothed out by the _____ and _____ located in the pons.
• The apneustic center _____ inspiration; the more powerful pneumotaxic center _____ inspiration.

Answer 29

Control of Respiration

• This basic rhythm is smoothed out by the apneustic and pneumotaxic centers located in the pons.
• The apneustic center prolongs inspiration; the more powerful pneumotaxic center limits inspiration.

Question 30

Control of Respiration

• Three chemical factors play a role in determining the magnitude of ventilation:
  
  1. ___
  2. ___
  3. ____________

Answer 30

Control of Respiration

• Three chemical factors play a role in determining the magnitude of ventilation:
  
  1. PCO₂,
  2. PO₂,
  3. H⁺ concentration of the arterial blood.

Question 31

Control of Respiration

• The dominant factor in the ongoing regulation of ventilation is ________, an increase of which is the most potent chemical stimulus for ________ ventilation.
• Changes in ________ alter ventilation by bringing about corresponding changes in the alter ____________ concentration, to which the central chemoreceptors are very sensitive.

Answer 31

Control of Respiration

• The dominant factor in the ongoing regulation of ventilation is arterial PCO₂, an increase of which is the most potent chemical stimulus for increasing ventilation.
• Changes in arterial PCO2 alter ventilation by bringing about corresponding changes in the alter brain-ECF H⁺ concentration, to which the central chemoreceptors are very sensitive.

Question 32

Control of Respiration

• The ________ are responsive to an increase in arterial H⁺ concentration, which likewise reflexly brings about _______.
• The resulting adjustment in arterial H⁺- generating CO₂ is important in maintaining the ________ balance of the body.

Answer 32

Control of Respiration

• The peripheral chemoreceptors are responsive to an increase in arterial H⁺ concentration, which likewise reflexly brings about increased ventilation.
• The resulting adjustment in arterial H⁺- generating CO₂ is important in maintaining the acid–base balance of the body.

Question 33

Control of Respiration

• The peripheral chemoreceptors also reflexly increase ______ in response to a marked reduction in ____________, serving as an emergency mechanism to increase respiration when ______ levels fall below the safety range provided by the plateau portion of the ____________.

Answer 33

Control of Respiration

• The peripheral chemoreceptors also reflexly increase ventilation in response to a marked reduction in arterial PO₂ (< 60 mmHg), serving as an emergency mechanism to increase respiration when arterial PO₂ levels fall below the safety range provided by the plateau portion of the O2-Hb curve.

Question 34

Control of Respiration

• Respiration activity can also be ______ modified.

Answer 34

Control of Respiration

• Respiration activity can also be voluntarily modified.