Describe the control of alveolar ventilation.
The most comprehensive answers were those structured as sensor-controller-effector with an
explanation of each part and how homeostasis was maintained. Insufficient detail was generally
provided as to how central and peripheral chemoreceptors were stimulated. A description of
central control was required, rather than listing nuclei or areas.
Many failed to address all three components of a control question and focused primarily on the
sensors. Many answers were just too brief and did not present enough information to
This is a question which Nunn's takes twenty pages to answer, so condensing it requires a bit of preparation. Ideally, the exam candidate will have a prefabricated answer stored in their cheek pouch, ready to regurgitate. Tabulated answers are almost always the best, and so here a series of tables which hopefully "present enough information to demonstrate understanding".
Carotid body glomus
|Aortic glomus cells - in the aortic arch, subclavian arteries and pulmonary trunk||
(branch of the vagus)
|Mechanoreceptors in bronchial and lung tissue||
|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|
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