L5. Control of breathing in exercise Flashcards
What are the three primary control mechanisms for breathing during exercise?
Feedforward, feedback, and adaptive control
What is the role of feedforward control in exercise?
It anticipates exercise and adjusts ventilation accordingly
Why is there no error signal for chemical feedback during mild to moderate exercise?
Arterial PCO2, pH, and PO2 remain constant
What is the concept of ‘cortical irradiation’ proposed by Krogh and Lindhard?
It explains anticipatory hyperventilation prior to exercise
What is the significance of the ‘Douglas Bag’ in breathing studies?
It was used to collect expired air for analyzing respiratory patterns
What are the three phases of ventilation during steady-state exercise?
Phase 1: Immediate rise, Phase 2: Gradual increase, Phase 3: Plateau
How does central command influence breathing during exercise?
It sends signals to increase ventilation based on expected activity
What experiment showed central command’s role in breathing?
Eldridge’s fictive locomotion experiments in decerebrate animals
What evidence supports the role of muscle afferents in breathing?
Crosse-perfused dog experiments showed increased ventilation from muscle signals
What is cardiodynamic hyperpnoea?
The hypothesis that increased cardiac output drives ventilation
How did heart transplant studies challenge cardiodynamic hyperpnoea?
Ventilation increased during exercise without neural control of cardiac output
What is CO2 flux sensing?
The idea that ventilation adjusts to the rate of CO2 transport
What experiments questioned CO2 flux sensing?
Studies showing inconsistent results when venous CO2 was artificially increased
What is the role of the carotid bodies in exercise?
They provide load compensation for ventilatory control
How does adaptive control influence breathing?
It allows the ventilatory system to calibrate responses over time
What experiment demonstrated learned ventilatory responses?
Training animals to exercise with added dead space normalized CO2 levels
What did Helen Wood’s experiment show about humans adapting to CO2 loads?
Training improved ventilatory control even with additional CO2
Why is redundancy important in respiratory control?
Multiple mechanisms ensure accurate ventilation even if one fails
What happens to ventilation during high-intensity exercise?
Ventilation increases disproportionately due to anaerobic metabolism
What role do feedforward mechanisms play in ventilatory control?
They dominate during mild to moderate exercise to prevent errors
What is the evidence for central command in humans?
Increased ventilation even in paralyzed patients with exercise simulation
What did studies on carotid body removal reveal?
Submaximal exercise ventilation is largely unaffected, but high-intensity responses are impaired
How does hyperventilation before exercise occur?
Anticipatory signals from the brain increase ventilation before movement starts
What is the significance of VCO2 in ventilation studies?
It represents the rate of CO2 production and helps analyze ventilatory efficiency
How does ventilation respond to changes in exercise intensity?
It increases linearly with CO2 production until the anaerobic threshold
What is the concept of ‘load compensation’ in carotid bodies?
They adjust their sensitivity to match the increased metabolic demands
What did experiments on patients with congenital chemoreceptor absence show?
Ventilatory control is partially innate but benefits from chemoreceptor feedback
What are the key stimuli for increased ventilation during exercise?
Central command, muscle afferents, and cardiac output
What happens to alveolar CO2 levels during exercise?
They show larger fluctuations but maintain a stable mean level
What did the artificial CO2 flux experiments conclude?
Inconsistent evidence for CO2 flux as a primary ventilatory driver
What is the role of perceived exertion in ventilation?
Higher perceived effort increases ventilatory drive
How does redundancy in control mechanisms benefit respiration?
Ensures stable ventilation despite individual mechanism failures
What did studies on ventilatory adaptation in goats reveal?
Animals can recalibrate their breathing to compensate for artificial changes
How does hyperventilation relate to unexplained breathlessness?
Some patients hyperventilate without clear physiological causes
What did Mitchell’s experiments on ventilatory learning demonstrate?
Animals adapt their breathing patterns to external respiratory challenges
How do ventilation and metabolism synchronize during exercise?
Feedforward systems anticipate and match ventilation to metabolic needs
What is the significance of the phase 1 ventilatory response?
It provides immediate ventilation increase at exercise onset
What is the relationship between tidal volume and ventilation?
Increases in tidal volume contribute to higher overall ventilation
What did Krogh and Lindhard conclude about central command?
It is a primary driver of anticipatory hyperventilation during exercise
What is the impact of hypercapnia on ventilatory responses during exercise?
Hypercapnia increases ventilatory drive to expel excess CO2
