Lecture 9 Comparative Respiration

Question 1

During inhalation in birds, what happens to the posterior air sacs?
a) They compress and release stale air into the lungs.
b) They expand and fill with fresh air directly from the environment.
c) They remain static and do not participate in air movement.
d) They compress and fill with stale air from the anterior air sacs.

Answer 1

Answer: b) They expand and fill with fresh air directly from the environment.

Question 2

What is the direction of airflow through the parabronchi in the bird’s lung?
a) From the anterior to posterior air sacs.
b) From the anterior air sacs directly to the environment.
c) From the posterior air sacs to the anterior air sacs.
d) From the lungs to the posterior air sacs.

Answer 2

Answer: c) From the posterior air sacs to the anterior air sacs.

Question 3

During exhalation in birds, which of the following occurs?
a) The anterior air sacs compress and discharge stale air stored in them.
b) The posterior air sacs expand and fill with fresh air.
c) The fresh air bypasses the lungs and is directly exhaled.
d) Stale air is sent back to the posterior air sacs for re-filtration.

Answer 3

Answer: a) The anterior air sacs compress and discharge stale air stored in them.

Question 4

What distinguishes avian respiration from mammalian respiration?
a) Airflow in bird lungs is bidirectional, ensuring continuous gas exchange.
b) Airflow in bird lungs is unidirectional, ensuring continuous gas exchange.
c) Air sacs in birds only store stale air without contributing to gas exchange.
d) Bird lungs exchange gases only during inhalation.

Answer 4

Answer: b) Airflow in bird lungs is unidirectional, ensuring continuous gas exchange.

Question 5

What is the primary characteristic of airflow in the parabronchi of avian lungs?
a) Bidirectional, with air flowing in and out through the same pathway.
b) Unidirectional, ensuring continuous and efficient gas exchange.
c) Circular, with air recirculating multiple times through the same capillaries.
d) Stochastic, with no defined direction of airflow.

Answer 5

Answer: b) Unidirectional, ensuring continuous and efficient gas exchange.

Question 6

How does the cross-current flow in bird lungs differ from counter-current flow found in fish gills?
a) Cross-current flow maximizes efficiency by having blood and air flow in the same direction.
b) In cross-current flow, blood intersects air at an angle, unlike the parallel flow in counter-current systems.
c) Cross-current flow uses capillaries thicker than those in counter-current systems.
d) Cross-current flow exchanges oxygen at lower efficiency than counter-current systems.

Answer 6

Answer: b) In cross-current flow, blood intersects air at an angle, unlike the parallel flow in counter-current systems.

Question 7

Why are air capillaries in bird lungs exceptionally thin?
a) To allow high-pressure air to flow through easily.
b) To facilitate efficient gas exchange with minimal diffusion distance.
c) To prevent air from escaping into the bloodstream.
d) To allow blood to flow directly into the parabronchi.

Answer 7

b)

Question 8

In the avian respiratory system, what is the main advantage of unidirectional airflow compared to tidal ventilation?
a) It allows air and blood to mix directly, increasing oxygen concentration.
b) It reduces the volume of air needed for gas exchange.
c) It ensures fresh air continuously flows over the respiratory surfaces, maximizing oxygen uptake.
d) It prevents carbon dioxide from diffusing back into the air sacs.

Answer 8

Answer: c) It ensures fresh air continuously flows over the respiratory surfaces, maximizing oxygen uptake.

Question 9

Which of the following best explains the role of air capillaries in avian lungs?
a) They act as storage units for fresh and stale air during respiration.
b) They create a high-pressure system to push air into the bloodstream.
c) They are the primary sites of gas exchange, facilitating oxygen diffusion into the blood.
d) They direct airflow into the anterior air sacs for expulsion during exhalation.

Answer 9

Answer: c) They are the primary sites of gas exchange, facilitating oxygen diffusion into the blood.

Question 10

Why are air capillaries in avian lungs described as “blind-ended”?
a) They allow air to circulate back to the air sacs.
b) They terminate without direct connection to larger bronchi, maximizing surface area for gas exchange.
c) They direct airflow into the posterior air sacs during exhalation.
d) They are blocked at one end to prevent stale air from exiting.

Answer 10

Answer: b) They terminate without direct connection to larger bronchi, maximizing surface area for gas exchange.

Question 11

What prevents pressure changes in the air capillaries of avian lungs during respiration?
a) The thick walls of the parabronchi.
b) The unidirectional airflow in the parabronchi.
c) The absence of direct ventilation in the lungs.
d) The expansion and contraction of the anterior air sacs.

Answer 11

Answer: c) The absence of direct ventilation in the lungs.

Question 12

How do the structural adaptations of air capillaries contribute to their function?
a) Their thick walls protect against pressure changes during high altitudes.
b) Their small diameter ensures minimal blood supply to conserve energy.
c) Their thin walls and high vascularization maximize oxygen and carbon dioxide exchange.
d) Their blind ends prevent air from mixing with blood.

Answer 12

Answer: c) Their thin walls and high vascularization maximize oxygen and carbon dioxide exchange.

Question 13

Which of the following statements about air capillaries in avian lungs is true?
a) Air capillaries are directly connected to anterior air sacs for gas exchange.
b) Gas exchange occurs only during inhalation because of pressure differences.
c) Air capillaries branch off parabronchi and are highly vascularized for efficient gas exchange.
d) Air capillaries are ventilated by muscular contractions during exhalation.

Answer 13

Answer: c) Air capillaries branch off parabronchi and are highly vascularized for efficient gas exchange.

Question 14

What unique feature of avian lungs ensures continuous gas exchange during both inhalation and exhalation?
a) The branching of air capillaries directly into blood vessels.
b) The presence of blind-ended parabronchi that store fresh air.
c) The combination of unidirectional airflow and non-ventilated lungs.
d) The alternate contraction of anterior and posterior air sacs.

Answer 14

Answer: c) The combination of unidirectional airflow and non-ventilated lungs.

Question 15

What is the primary mechanism of gas movement in the alveoli?
a) Bulk flow
b) Diffusion
c) Convection
d) Osmosis

Answer 15

Answer: b) Diffusion

Question 16

Why does diffusion become the primary method of gas movement in the alveoli?
a) The airways are too narrow for bulk flow to continue effectively.
b) Gas molecules are actively pumped across the alveolar membrane.
c) Bulk flow is inhibited by high oxygen concentration.
d) The air in the alveoli is stationary, requiring diffusion for movement.

Answer 16

Answer: a) The airways are too narrow for bulk flow to continue effectively.

Question 17

What factor limits the motion of gases in the deep ends of the bronchioles?
a) High pressure from bulk flow
b) Small radius of the airways
c) Decreased concentration gradients
d) Increased velocity of air molecules

Answer 17

Answer: b) Small radius of the airways

Question 18

Which two processes alternate during gas transport in animals?
a) Osmosis and bulk flow
b) Diffusion and active transport
c) Convection (bulk flow) and diffusion
d) Respiration and exhalation

Answer 18

Answer: c) Convection (bulk flow) and diffusion

Question 19

What happens to air molecules once they reach the alveoli?
a) They dissolve in a liquid layer before crossing into the blood supply.
b) They are directly transported by red blood cells without dissolving.
c) They undergo convection to reach the bloodstream.
d) They are exhaled directly back out of the lungs.

Answer 19

Answer: a) They dissolve in a liquid layer before crossing into the blood supply.

Question 20

What is the approximate distance a gas molecule must travel from the alveolus wall to the red blood cell?
a) 0.1 m
b) 0.01 m
c) 0.0001 m
d) 1 m

Answer 20

Answer: c) 0.0001 m

Question 21

Why is diffusion the primary method of gas transport in the alveoli?
a) The distance is too short for convection to be efficient.
b) The air pressure is too low for bulk flow.
c) Gas molecules are actively pumped through the alveolar membrane.
d) Convection stops completely in the alveoli.

Answer 21

Answer: a) The distance is too short for convection to be efficient.

Question 22

What role does bulk flow play in gas transport in the respiratory system?
a) It only transports gases from the mouth to the alveoli.
b) It drives ventilation and circulation, moving gases over large distances.
c) It is responsible for dissolving gases at the alveolar surface.
d) It pumps oxygen directly into red blood cells.

Answer 22

Answer: b) It drives ventilation and circulation, moving gases over large distances.

Question 23

What happens after a red blood cell picks up oxygen in the alveoli?
a) The oxygen diffuses back into the lungs for exhalation.
b) The oxygen is transported via convection to tissues where it is used.
c) The oxygen is stored in the alveolar liquid layer.
d) The oxygen dissolves again in the bloodstream before use.

Answer 23

b) The oxygen is transported via convection to tissues where it is used.

Question 24

What is the difference in scale between bulk flow in the respiratory system and diffusion in the alveoli?
a) Bulk flow covers much smaller distances compared to diffusion.
b) Diffusion occurs over significantly larger distances than bulk flow.
c) Bulk flow transports gases over larger distances, while diffusion is effective over short distances.
d) Both processes occur over the same distances.

Answer 24

Answer: c) Bulk flow transports gases over larger distances, while diffusion is effective over short distances.

Question 25

Which process is responsible for ventilation in the respiratory system?
a) Diffusion
b) Osmosis
c) Bulk flow
d) Active transport

Answer 25

Answer: c) Bulk flow

Question 26

Which type of alveolar cells are primarily responsible for gas exchange in the lungs?
a) Type I alveolar cells
b) Type II alveolar cells
c) Alveolar macrophages
d) Capillary endothelial cells

Answer 26

Answer: a) Type I alveolar cells

Question 27

What is the main function of Type II alveolar cells?
a) To facilitate oxygen diffusion into the bloodstream
b) To secrete surfactants and maintain fluid balance in the lungs
c) To transport carbon dioxide from the blood to the alveoli
d) To provide structural support for Type I alveolar cells

Answer 27

Answer: b) To secrete surfactants and maintain fluid balance in the lungs

Question 28

What role do surfactants play in the respiratory system?
a) They promote oxygen binding to red blood cells.
b) They reduce surface tension in the alveoli, making it easier to breathe.
c) They facilitate the movement of air from the trachea to the alveoli.
d) They increase blood flow to the capillaries surrounding the alveoli.

Answer 28

Answer: b) They reduce surface tension in the alveoli, making it easier to breathe.

Question 29

Where are capillaries located in relation to the alveoli?
a) Inside the alveolar walls
b) On the outer surface of the alveoli
c) Between the Type I and Type II alveolar cells
d) At the terminal bronchioles

Answer 29

b)

Question 30

What is the primary function of the capillaries surrounding the alveoli?
a) To secrete surfactants
b) To exchange oxygen and carbon dioxide with the alveoli
c) To maintain structural integrity of the alveolar walls
d) To regulate fluid balance in the lungs

Answer 30

b)

Question 31

What percentage of air in the airways after a resting inhalation is fresh air?
a) 100%
b) 50%
c) 12%
d) 88%

Answer 31

Answer: c) 12%

Question 32

What does the partial pressure of oxygen (PO2) in the alveoli depend on?
a) The oxygen concentration in the environment only.
b) The rate of ventilation and the rate of oxygen uptake by capillaries.
c) The amount of stale air in the alveoli.
d) The size of the alveoli.

Answer 32

Answer: b) The rate of ventilation and the rate of oxygen uptake by capillaries.

Question 33

What is the primary role of the diaphragm in mammalian respiration?
a) To actively push air out of the lungs during exhalation
b) To increase the size of the chest cavity during inhalation
c) To maintain constant pressure in the lungs
d) To contract during both inhalation and exhalation

Answer 33

Answer: b) To increase the size of the chest cavity during inhalation

Question 34

What happens to the pressure inside the lungs when the chest cavity volume increases?
a) Pressure increases, forcing air out of the lungs
b) Pressure decreases, allowing air to flow into the lungs
c) Pressure remains constant
d) Pressure increases slightly, causing air to mix with stale air

Answer 34

Answer: b) Pressure decreases, allowing air to flow into the lungs

Question 35

What does lung compliance refer to?
a) The ability of the lungs to resist stretching during inhalation
b) How easily the lungs stretch during inhalation
c) The ability of the lungs to contract during exhalation
d) How much oxygen the lungs can store

Answer 35

Answer: b) How easily the lungs stretch during inhalation

Question 36

How do surfactants improve lung compliance?
a) By reducing surface tension through disruption of hydrogen bonds in the alveolar fluid
b) By strengthening the walls of alveoli to resist collapsing
c) By increasing the amount of oxygen in the lungs
d) By removing fluid from the alveoli

Answer 36

Answer: a) By reducing surface tension through disruption of hydrogen bonds in the alveolar fluid

Question 37

Which cells in the alveoli are responsible for producing surfactants?
a) Type I alveolar cells
b) Type II alveolar cells
c) Alveolar macrophages
d) Capillary endothelial cells

Answer 37

Answer: b) Type II alveolar cells

Question 38

What condition is caused by the lack of surfactants in premature infants?
a) Pneumonia
b) Bronchitis
c) Infant respiratory distress syndrome
d) Pulmonary fibrosis

Answer 38

Answer: c) Infant respiratory distress syndrome

Question 39

What treatment can help premature infants with collapsed alveoli due to lack of surfactants?
a) Supplemental oxygen
b) Artificial surfactants administered into the lungs
c) Diuretics to remove fluid from the lungs
d) Mechanical ventilation without any chemical treatment

Answer 39

Answer: b) Artificial surfactants administered into the lungs

Question 40

What regulates the rhythmic process of ventilation in vertebrates?
a) Peripheral chemoreceptors
b) Central pattern generator (CPG)
c) Respiratory muscles
d) Pulmonary stretch receptors

Answer 40

Answer: b) Central pattern generator (CPG)

Question 41

What is the primary regulator of breathing in air-breathing vertebrates?
a) Oxygen
b) Carbon dioxide
c) Blood pressure
d) Nitrogen

Answer 41

Answer: b) Carbon dioxide

Question 42

Where are the central chemoreceptors that regulate breathing located?
a) Carotid arteries
b) Aortic arch
c) Medulla of the brain
d) Lungs

Answer 42

Answer: c) Medulla of the brain

Question 43

What do central chemoreceptors primarily sense to regulate ventilation?
a) Oxygen levels in the blood
b) Partial pressure of nitrogen
c) Changes in blood pH
d) Total lung capacity

Answer 43

Answer: c) Changes in blood pH

Question 44

What is the primary function of peripheral chemoreceptors in air-breathing vertebrates?
a) To sense changes in blood pH
b) To sense falling oxygen levels in the blood
c) To monitor nitrogen levels in the environment
d) To regulate respiratory muscle contractions

Answer 44

Answer: b) To sense falling oxygen levels in the blood

Question 45

Which structures house the peripheral chemoreceptors in air-breathing vertebrates?
a) Medulla oblongata and cerebral cortex
b) Carotid bodies and aortic bodies
c) Alveoli and pulmonary capillaries
d) Trachea and bronchi

Answer 45

Answer: b) Carotid bodies and aortic bodies

Question 46

Why is CO2 the primary regulator of breathing in air-breathing vertebrates?
a) Because CO2 directly stimulates the respiratory muscles.
b) Because high levels of CO2 decrease blood pH, which is sensed by chemoreceptors.
c) Because CO2 levels determine oxygen diffusion into the blood.
d) Because CO2 stimulates pulmonary stretch receptors.

Answer 46

Answer: b) Because high levels of CO2 decrease blood pH, which is sensed by chemoreceptors.

Question 47

Which chemoreceptors are responsible for most of the regulation of breathing in air-breathing vertebrates?
a) Peripheral chemoreceptors in the carotid bodies
b) Central chemoreceptors in the medulla
c) Pulmonary stretch receptors in the lungs
d) Baroreceptors in the aorta

Answer 47

Answer: b) Central chemoreceptors in the medulla

Question 48

Which of the following correctly describes the roles of both central and peripheral chemoreceptors in regulating breathing?

a) Central chemoreceptors detect falling oxygen levels, while peripheral chemoreceptors sense changes in blood pH.
b) Central chemoreceptors primarily monitor pH changes in the cerebrospinal fluid, while peripheral chemoreceptors detect falling oxygen levels in the blood.
c) Central chemoreceptors are located in the carotid and aortic bodies, while peripheral chemoreceptors are found in the medulla of the brain.
d) Central chemoreceptors and peripheral chemoreceptors both primarily monitor blood pressure.

Answer 48

Answer:
b) Central chemoreceptors primarily monitor pH changes in the cerebrospinal fluid, while peripheral chemoreceptors detect falling oxygen levels in the blood.

Question 49

What triggers peripheral chemoreceptors in air-breathing vertebrates to increase ventilation?
a) Rising levels of carbon dioxide in the medulla
b) Falling levels of oxygen in the blood
c) Increasing pH in the cerebrospinal fluid
d) Rising levels of nitrogen in the lungs

Answer 49

Answer:
b) Falling levels of oxygen in the blood

Question 50

Which of the following correctly pairs the sensors involved in regulating respiratory rate and their functions?

a) Central chemoreceptors: Located in the brainstem, sense CO2 and proton (H⁺) concentrations;
Peripheral chemoreceptors: Located in carotid and aortic bodies, sense O2 and proton (H⁺) concentrations.

b) Central chemoreceptors: Located in the aortic bodies, sense O2 and CO2 levels;
Peripheral chemoreceptors: Located in carotid arteries, sense blood pressure only.

c) Central chemoreceptors: Located in the carotid bodies, sense oxygen levels;
Peripheral chemoreceptors: Located in the brainstem, sense carbon dioxide and blood pH.

d) Central chemoreceptors: Located in the brainstem, sense O2 and blood pressure;
Peripheral chemoreceptors: Located in carotid and aortic bodies, monitor heart rate.

Answer 50

a)

Question 51

Which sensory structures detect rising CO2 and proton (H⁺) levels to initiate the breathing response?
a) Afferent neurons in the lungs
b) Peripheral chemoreceptors in the carotid and aortic bodies and central chemoreceptors in the brainstem
c) Pulmonary stretch receptors in the alveoli
d) Baroreceptors in the arteries

Answer 51

Answer: b) Peripheral chemoreceptors in the carotid and aortic bodies and central chemoreceptors in the brainstem

Question 52

What happens to CO2 and O2 levels in the blood as a result of the effector response during increased physical activity?
a) Blood CO2 levels rise, and O2 levels fall.
b) Blood CO2 levels fall, and O2 levels rise.
c) Blood CO2 and O2 levels remain unchanged.
d) Blood CO2 levels rise, but O2 levels remain constant.

Answer 52

Answer: b) Blood CO2 levels fall, and O2 levels rise.