mark wrote:
Quote:
9. The resulting respiratory minute volume is markedly increased by:
a. a lowered CSF pH
b. an arterial PO2 of 10kPa (75mmHg)
c. chronic anaemia to Hb content of 5gm per 100 ml
d. increased blood pH to 7.6
e. breathing atmosphere air with 0.03 per cent carbon monoxide added
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This question is asking about the regulation of minute ventilation by both the peripheral and central chemoreceptors.
The central chemoreceptors respond to alterations in CSF hydrogen ion concentration. As the CSF has a low protein count the buffering capacity is reduced. small alterations of BBB permaeable carbon dioxide tensions are therefore picked up by the central chemoreceptors. The response to hypercarbia is an increased minute ventilation.
peripheral chemoreceptors located in the carotid and aortic bodies sense changes in arterial oygen tensions and not oxygen content. therefore the presence of carbon monoxide and chronic anaemia do not alter these receptors and their firing rates.
the henderson hasselbach equation dictates that in the presence of an alkolosis(raised bicarbonate ion concentration) in order to maintain the pH the carbon dioxide levels will need to rise and hence hypOventilation occurs.
Linear Mode
