How is alveolar ventilation regulated?
This is a core topic (syllabus Level 1) and a high level of understanding was expected. Overall
candidates failed to demonstrate sufficient depth and breadth in their knowledge. A
structured response considering the three basic elements underpinning the control of
alveolar ventilation (the Sensors, Central integration and control and the Effectors) was core
material. A detailed description of each was expected.
This question is essentially identical to Question 13 from the second paper of 2015 and Question 1 from the first paper of 2015, except the examiner comments this time were much more cranky.
Sensor | Stimulus | Afferent nerve |
Carotid body glomus |
|
Glossopharyngeal |
Aortic glomus cells - in the aortic arch, subclavian arteries and pulmonary trunk |
|
Aortic nerve (branch of the vagus) |
Central chemoreceptors |
|
- |
Mechanoreceptors in bronchial and lung tissue |
|
Vagus |
Controller | Role | Efferents and effectors |
Nucleus retroambigualis | Expiratory function |
Upper motor neuron axons to contralateral expiratory muscles |
Nucleus paraambigualis | Inspiratory function |
Upper motor neuron axons to contralateral inspiratory muscles |
Nucleus ambiguous | Airway dilator function |
Vagus nerve: to (larynx, pharynx and muscularis uvulae) Glossopharyngeus muscle to stylopharyngeus muscle |
Pre-Bötzinger complex | Respiratory pacemaker ("central pattern generator") | Interneurons connecting to other respiratory control regions |
Bötzinger complex | Expiratory function |
Inhibitory interneurons to phrenic motor neurons and other respiratory control regions |
Pontine respiratory group |
Integrates descending control of respiration from the CNS |
Interneurons connecting to other respiratory control regions |
Cerebral cortex | Volitional and behavioural respiratory control | Pontine respiratory group |
Wolff, Christopher B. "The physiological control of respiration." Molecular aspects of medicine 13.6 (1992): 445-567.
Henderson, V. E., and E. Horne Craigie. "On the respiratory centre." American Journal of Physiology-Legacy Content115.3 (1936): 520-529.
Remmers, John E. "A century of control of breathing." American journal of respiratory and critical care medicine172.1 (2005): 6-11.
Richter, D. W., F. Heyde, and M. Gabriel. "Intracellular recordings from different types of medullary respiratory neurons of the cat." Journal of neurophysiology 38.5 (1975): 1162-1171.
López-Barneo, J., et al. "Carotid body oxygen sensing." European Respiratory Journal 32.5 (2008): 1386-1398.
Prabhakar, Nanduri R., and Ying-Jie Peng. "Peripheral chemoreceptors in health and disease." Journal of Applied Physiology 96.1 (2004): 359-366.
Atanasova, Dimitrinka Y., Michail E. Iliev, and Nikolai E. Lazarov. "Morphology of the rat carotid body." Biomedical Reviews 22 (2011): 41-55.
Ortega‐Sáenz, Patricia, et al. "Cellular properties and chemosensory responses of the human carotid body." The Journal of physiology 591.24 (2013): 6157-6173.
López-Barneo, José. "Oxygen sensing and stem cell activation in the hypoxic carotid body." Cell and tissue research 372.2 (2018): 417-425.
Nattie, Eugene. "Why do we have both peripheral and central chemoreceptors?." Journal of Applied Physiology 100.1 (2006): 9-10.
Smith, Curtis A., et al. "Response time and sensitivity of the ventilatory response to CO2 in unanesthetized intact dogs: central vs. peripheral chemoreceptors." Journal of Applied Physiology 100.1 (2006): 13-19.
Lahiri, S., et al. "Relative responses of aortic body and carotid body chemoreceptors to carboxyhemoglobinemia." Journal of Applied Physiology 50.3 (1981): 580-586.
Lahiri, S., et al. "Relative responses of aortic body and carotid body chemoreceptors to hypotension." Journal of Applied Physiology 48.5 (1980): 781-788.
Prabhakar, Nanduri R. "O2 and CO2 detection by the carotid and aortic bodies." Chemosensory Transduction. Academic Press, 2016. 321-338.
Coleridge, Hazel, J. C. G. Coleridge, and A. Howe. "A search for pulmonary arterial chemoreceptors in the cat, with a comparison of the blood supply of the aortic bodies in the new‐born and adult animal." The Journal of physiology 191.2 (1967): 353-374.
Honda, Yoshiuki. "Respiratory and circulatory activities in carotid body-resected humans." Journal of Applied Physiology 73.1 (1992): 1-8.
Nattie, Eugene, and Aihua Li. "Central chemoreceptors: locations and functions." Comprehensive Physiology 2.1 (2011): 221-254.
Li, Aihua, Shawn Zhou, and Eugene Nattie. "Simultaneous inhibition of caudal medullary raphe and retrotrapezoid nucleus decreases breathing and the CO2 response in conscious rats." The Journal of physiology 577.1 (2006): 307-318.
Phillipson, ELIOT A., James Duffin, and Joel D. Cooper. "Critical dependence of respiratory rhythmicity on metabolic CO2 load." Journal of Applied Physiology 50.1 (1981): 45-54.
Wang, Wengang, Stefania Risso Bradley, and George B. Richerson. "Quantification of the response of rat medullary raphe neurones to independent changes in pHo and PCO2." The Journal of Physiology 540.3 (2002): 951-970.
Ullmann, Elisabeth. "The two original papers by Hering and Breuer submitted by Hering to the KK Akademie der Wissenschaften zu Wien in 1868." Ciba Foundation Symposium‐Breathing: Hering‐Breuer Centenary Symposium. Chichester, UK: John Wiley & Sons, Ltd., 1970
Tryfon, S., et al. "Hering-Breuer reflex in normal adults and in patients with chronic obstructive pulmonary disease and interstitial fibrosis." Respiration 68.2 (2001): 140-144.