Describe the physiological consequences of a progressive rise in blood carbon dioxide levels.

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College Answer

Candidates were expected to present a mechanistic description the neuro-cellular events 
following a rise in PaCO2 such as changes in H+ in CSF, stimulation of central and peripheral 
chemoreceptors and neural pathways that lead to stimulation of respiratory centre. A 
systematic approach to the question with in-depth details of direction and magnitude of 
physiologic changes were required. Most candidates presented graphs of cerebral blood 
flow and tidal volume changes with increasing PaCO2. Common omissions included other 
important points,such as the cardiovascular and respiratory effects of rising CO2 and the 
rightward shift of oxygen haemoglobin curve.