L5. Control of breathing in exercise

Question 1

What are the three primary control mechanisms for breathing during exercise?

Answer 1

Feedforward, feedback, and adaptive control

Question 2

What is the role of feedforward control in exercise?

Answer 2

It anticipates exercise and adjusts ventilation accordingly

Question 3

Why is there no error signal for chemical feedback during mild to moderate exercise?

Answer 3

Arterial PCO2, pH, and PO2 remain constant

Question 4

What is the concept of ‘cortical irradiation’ proposed by Krogh and Lindhard?

Answer 4

It explains anticipatory hyperventilation prior to exercise

Question 5

What is the significance of the ‘Douglas Bag’ in breathing studies?

Answer 5

It was used to collect expired air for analyzing respiratory patterns

Question 6

What are the three phases of ventilation during steady-state exercise?

Answer 6

Phase 1: Immediate rise, Phase 2: Gradual increase, Phase 3: Plateau

Question 7

How does central command influence breathing during exercise?

Answer 7

It sends signals to increase ventilation based on expected activity

Question 8

What experiment showed central command’s role in breathing?

Answer 8

Eldridge’s fictive locomotion experiments in decerebrate animals

Question 9

What evidence supports the role of muscle afferents in breathing?

Answer 9

Crosse-perfused dog experiments showed increased ventilation from muscle signals

Question 10

What is cardiodynamic hyperpnoea?

Answer 10

The hypothesis that increased cardiac output drives ventilation

Question 11

How did heart transplant studies challenge cardiodynamic hyperpnoea?

Answer 11

Ventilation increased during exercise without neural control of cardiac output

Question 12

What is CO2 flux sensing?

Answer 12

The idea that ventilation adjusts to the rate of CO2 transport

Question 13

What experiments questioned CO2 flux sensing?

Answer 13

Studies showing inconsistent results when venous CO2 was artificially increased

Question 14

What is the role of the carotid bodies in exercise?

Answer 14

They provide load compensation for ventilatory control

Question 15

How does adaptive control influence breathing?

Answer 15

It allows the ventilatory system to calibrate responses over time

Question 16

What experiment demonstrated learned ventilatory responses?

Answer 16

Training animals to exercise with added dead space normalized CO2 levels

Question 17

What did Helen Wood’s experiment show about humans adapting to CO2 loads?

Answer 17

Training improved ventilatory control even with additional CO2

Question 18

Why is redundancy important in respiratory control?

Answer 18

Multiple mechanisms ensure accurate ventilation even if one fails

Question 19

What happens to ventilation during high-intensity exercise?

Answer 19

Ventilation increases disproportionately due to anaerobic metabolism

Question 20

What role do feedforward mechanisms play in ventilatory control?

Answer 20

They dominate during mild to moderate exercise to prevent errors

Question 21

What is the evidence for central command in humans?

Answer 21

Increased ventilation even in paralyzed patients with exercise simulation

Question 22

What did studies on carotid body removal reveal?

Answer 22

Submaximal exercise ventilation is largely unaffected, but high-intensity responses are impaired

Question 23

How does hyperventilation before exercise occur?

Answer 23

Anticipatory signals from the brain increase ventilation before movement starts

Question 24

What is the significance of VCO2 in ventilation studies?

Answer 24

It represents the rate of CO2 production and helps analyze ventilatory efficiency

Question 25

How does ventilation respond to changes in exercise intensity?

Answer 25

It increases linearly with CO2 production until the anaerobic threshold

Question 26

What is the concept of ‘load compensation’ in carotid bodies?

Answer 26

They adjust their sensitivity to match the increased metabolic demands

Question 27

What did experiments on patients with congenital chemoreceptor absence show?

Answer 27

Ventilatory control is partially innate but benefits from chemoreceptor feedback

Question 28

What are the key stimuli for increased ventilation during exercise?

Answer 28

Central command, muscle afferents, and cardiac output

Question 29

What happens to alveolar CO2 levels during exercise?

Answer 29

They show larger fluctuations but maintain a stable mean level

Question 30

What did the artificial CO2 flux experiments conclude?

Answer 30

Inconsistent evidence for CO2 flux as a primary ventilatory driver

Question 31

What is the role of perceived exertion in ventilation?

Answer 31

Higher perceived effort increases ventilatory drive

Question 32

How does redundancy in control mechanisms benefit respiration?

Answer 32

Ensures stable ventilation despite individual mechanism failures

Question 33

What did studies on ventilatory adaptation in goats reveal?

Answer 33

Animals can recalibrate their breathing to compensate for artificial changes

Question 34

How does hyperventilation relate to unexplained breathlessness?

Answer 34

Some patients hyperventilate without clear physiological causes

Question 35

What did Mitchell’s experiments on ventilatory learning demonstrate?

Answer 35

Animals adapt their breathing patterns to external respiratory challenges

Question 36

How do ventilation and metabolism synchronize during exercise?

Answer 36

Feedforward systems anticipate and match ventilation to metabolic needs

Question 37

What is the significance of the phase 1 ventilatory response?

Answer 37

It provides immediate ventilation increase at exercise onset

Question 38

What is the relationship between tidal volume and ventilation?

Answer 38

Increases in tidal volume contribute to higher overall ventilation

Question 39

What did Krogh and Lindhard conclude about central command?

Answer 39

It is a primary driver of anticipatory hyperventilation during exercise

Question 40

What is the impact of hypercapnia on ventilatory responses during exercise?

Answer 40

Hypercapnia increases ventilatory drive to expel excess CO2