Section 7

Question 1

What are the three components of neural control of respiration?

Answer 1

1. Generation of the alternating inspiration/expiration rhythm: This occurs in the medullary respiratory center. Dorsal respiratory group (DRG) neurons are inspiratory, while ventral respiratory group (VRG) neurons are both inspiratory and expiratory.
2. Regulation of the level of respiration (rate and depth) to match metabolism: Controlled by the brain stem under the influence of receptors involved in respiration.
3. Modulation of respiratory activity for other purposes: Involves voluntary actions like speech and involuntary actions like cough or sneeze.

Question 2

What are the three classes of pulmonary receptors, and what are their functions?

Answer 2

1. Slowly adapting receptors: These have endings in the airway smooth muscle and respond to changes in lung volume. Their rate of discharge increases as the lungs inflate.
2. Rapidly adapting receptors: These have endings in the epithelia of larger airways and respond to both mechanical and chemical stimuli. Activation can cause airway narrowing and cough, serving as a protective reflex. Their activation can also induce mucus production to trap inhaled particles.
3. C-fibres: Located close to pulmonary capillaries, these receptors detect increases in pulmonary arterial pressure and pulmonary edema. They also respond to chemical stimuli like capsaicin, signaling inflammation. Activation leads to bronchoconstriction and rapid shallow breathing.

Question 3

What is the function of slowly adapting receptors among pulmonary receptors?

Answer 3

Slowly adapting receptors have endings in the airway smooth muscle and respond to changes in lung volume. Their rate of discharge increases as the lungs inflate.

Question 4

What role do rapidly adapting receptors play among pulmonary receptors, and what stimuli do they respond to?

Answer 4

Rapidly adapting receptors have endings in the epithelia of larger airways. They respond to both mechanical and chemical stimuli, and their activation can cause airway narrowing and induce cough as a protective reflex. They also trigger mucus production to trap inhaled particles.

Question 5

What is the function of C-fibres among pulmonary receptors, and what stimuli do they respond to?

Answer 5

C-fibres, located close to pulmonary capillaries, detect increases in pulmonary arterial pressure and pulmonary edema. They also respond to chemical stimuli like capsaicin, signaling inflammation. Activation of C-fibres leads to bronchoconstriction and rapid shallow breathing.

Question 6

What is the role of Rib Cage Receptors in respiration?

Answer 6

The muscles of the chest wall, including muscle spindles and a few Golgi tendon organs, have unclear roles in respiration. Muscle spindles detect discrepancies in chest wall distention, possibly related to posture regulation and respiratory control.

Question 7

Do diaphragm receptors play a significant role in respiration?

Answer 7

The diaphragm contains very few mechanical receptors, suggesting that its key roles in respiration may have limited these receptor types. However, the diaphragm has many small myelinated and unmyelinated afferents responding to local metabolic conditions.

Question 8

How is the maintenance of arterial blood gases achieved concerning breathing?

Answer 8

The maintenance of arterial blood gases is achieved by varying the rate and depth of breathing to match metabolic demand. When metabolism increases, ventilation increases to maintain constant arterial PO2 and PCO2.

Question 9

What are the chemical factors that play an important role in regulating ventilation?

Answer 9

The chemical factors include PO2 and PCO2. They are crucial in providing information about the chemical composition of the blood to the medullary control center, helping regulate ventilation to match metabolic demand.

Question 10

Where are the peripheral chemoreceptors that monitor arterial PO2 located?

Answer 10

The peripheral chemoreceptors monitoring arterial PO2 are found in the carotid bodies and the aortic bodies.

Question 11

How do carotid chemoreceptors respond to changes in arterial PO2?

Answer 11

Carotid chemoreceptors respond to changes in arterial PO2. However, they are relatively insensitive to small changes until the PO2 drops below 60 mmHg, the level at which oxygen desaturation could impair peripheral tissue functioning.

Question 12

What is the effect of activating carotid chemoreceptors on ventilation?

Answer 12

Activation of carotid chemoreceptors causes an increase in ventilation to raise arterial PO2. This response is significant when arterial PO2 drops below 60 mmHg.

Question 13

How do aortic chemoreceptors respond to changes in oxygen content?

Answer 13

Aortic chemoreceptors respond to changes in oxygen content. Activation of aortic chemoreceptors occurs when oxygen content decreases but does not affect ventilation; instead, it increases cardiac output to enhance systemic oxygen delivery.

Question 14

What is the most important factor regulating minute-to-minute ventilation when at rest?

Answer 14

Carbon dioxide is the most important factor regulating minute-to-minute ventilation when at rest.

Question 15

How do slight increases in PCO2 affect ventilation?

Answer 15

Even slight increases in PCO2 stimulate the respiratory centres to increase ventilation to remove the excess CO2.

Question 16

What happens when PCO2 falls?

Answer 16

A fall in PCO2 decreases ventilation to allow metabolically-derived CO2 to accumulate until PCO2 is normalized.

Question 17

Where are the central chemoreceptors located?

Answer 17

The central chemoreceptors are located in the medulla near the respiratory centres.

Question 18

Do peripheral chemoreceptors play a significant role in the control of ventilation by CO2?

Answer 18

No, peripheral chemoreceptors do not play any significant role in the control of ventilation by CO2; it is primarily regulated by central chemoreceptors.

Question 19

How does an increase in arterial PCO2 affect brain extracellular fluid PCO2?

Answer 19

An increase in arterial PCO2 causes an increase in brain extracellular fluid PCO2 because carbon dioxide readily crosses the blood-brain barrier.

Question 20

According to the law of mass action, what happens when CO2 increases?

Answer 20

According to the law of mass action, if CO2 increases, there is a rise in H+.

Question 21

How does the increase in H+ influence ventilation?

Answer 21

The increase in H+ stimulates the central chemoreceptors to increase ventilation.

Question 22

What reverses the increase in H+?

Answer 22

As the excess PCO2 is exhaled, the reaction reverses to decrease H+ again.

Question 23

Why do plasma H+ concentrations not influence respiration?

Answer 23

Plasma H+ concentrations do not influence respiration because H+ does not readily cross the blood-brain barrier.

Question 24

Can voluntary inhibition of breathing override the effects of increasing H+?

Answer 24

No, the effects of increasing H+ are so powerful that they can override voluntary inhibition of breathing.

Question 25

Which of the following are mechanical control of breathing?

Aortic bodies,
Cardiac receptors,
Carotid bodies,
Decrease in H-,
Diaphragm receptors,
Increase in Arterial PCO2,
Increase in brain Na2+,
Increase in brain-ECF H+,
Increase in Arterial P02,
Pulmonary receptors,
Rib cage receptors

Answer 25

Diaphragm receptors,
Pulmonary receptors,
Rib cage receptors

Question 26

Which of the following are chemical control of breathing?

Aortic bodies,
Cardiac receptors,
Carotid bodies,
Decrease in H-,
Diaphragm receptors,
Increase in Arterial PCO2,
Increase in brain Na2+,
Increase in brain-ECF H+,
Increase in Arterial P02,
Pulmonary receptors,
Rib cage receptors

Answer 26

Aortic bodies,
Carotid bodies,
Increase in Arterial PCO2,
Increase in brain-ECF H+,

Question 27

Which of the following are NEITHER mechanical control nor chemical control of breathing?

Aortic bodies,
Cardiac receptors,
Carotid bodies,
Decrease in H-,
Diaphragm receptors,
Increase in Arterial PCO2,
Increase in brain Na2+,
Increase in brain-ECF H+,
Increase in Arterial P02,
Pulmonary receptors,
Rib cage receptors

Answer 27

Cardiac receptors,
Increase in Arterial P02,
Decrease in H-,
Increase in brain Na2+,

Question 28

As you know by now, there are many physiological adaptations which occur at the onset and during
the course of exercise.

From what you have learned so far, from this Module and from others, describe why you think ventilation increases during exercise.

Answer 28

think about it and answer the rest of the flashcards

Question 29

What is the effect of exercise on alveolar ventilation?

Answer 29

During exercise, alveolar ventilation can increase up to 20-fold.

Question 30

Do PO2, PCO2, and H+ play significant roles in the increase in ventilation during exercise?

Answer 30

No, during exercise, arterial PO2 generally remains normal or may even be slightly elevated, PCO2 also remains normal or may even decrease, and brain extracellular fluid H+ remains constant. These factors play little role in the increase in ventilation during exercise.

Question 31

What are some factors that contribute to the exercise-induced increase in ventilation?

Answer 31

Several factors contribute to the exercise-induced increase in ventilation, including reflexes originating from body movements (muscle mechanoreceptors), epinephrine release, increased body temperature, and impulses from the cerebral cortex.

Question 32

How do muscle mechanoreceptors contribute to the increase in ventilation during exercise?

Answer 32

Muscle mechanoreceptors excited during muscle contraction reflexly stimulate the respiratory centre to increase ventilation.

Question 33

What role does the release of epinephrine play in the increase in ventilation during exercise?

Answer 33

The release of epinephrine from the adrenal medulla stimulates ventilation during exercise.

Question 34

How does increased body temperature contribute to the control of ventilation during exercise?

Answer 34

Increasing body temperature, as seen during exercise, increases ventilation (similar to what occurs during fever), and this is a likely contributor to the control of ventilation.

Question 35

What is the feedforward mechanism that occurs at the onset of exercise?

Answer 35

At the onset of exercise, it is believed that the motor areas of the cerebral cortex simultaneously stimulate the medullary respiratory neurons and activate the motor neurons of the exercising muscles. This is a feedforward mechanism that can occur before any homeostatic factors could occur.