Explain the control of breathing.
This question was generally well done. It was expected answers would include discussion of
the three core elements of sensors, a central controller and effectors. Central control involves
three main groups of neurones in the brainstem with some cortical voluntary control also
possible. More in depth answers included graphs of the ventilatory response to oxygen and
carbon dioxide tensions.
This question is essentially identical to Question 13 from the second paper of 2015, except that this time the college also expected graphs to illustrate the ventilatory response to oxygen and carbon dioxide. These graphs can be found in any decent physiology textbook, and they usually look like this:
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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