4. Chemical Control Of Breathing Flashcards
What do automatic respiratory centres in the brainstem do?
Activate respiratory muscles rhythmically and subconsciously
Set automatic rhythm for contraction of respiratory muscles
What do peripheral chemoreceptors sense?
pO2, pCO2, pH
What do central chemoreceptors sense?
pH and pCO2
Where are carotid bodies located?
Bifurcation of common carotid arteries
Where are aortic bodies located?
Located in aortic arch
What are the carotid bodies and aortic bodies sensitive to?
Decreases in arterial pO2 although high pCO2 and low pH also stimulate
What are the peripheral chemoreceptors?
Carotid bodies and aortic bodies
What is the major function of the carotid and aortic bodies?
Sense hypoxaemia and signal cells in the medulla to increase ventilation
What are the chemical sensing cells in the carotid bodies?
Type I glomus cells
What happens if peripheral chemoreceptors sense low pO2 and/or high pCO2?
They will feed back to medulla respiratory centres to increase minute ventilation, leads to increase in pO2 and decrease in pCO2
Where are central chemoreceptors located?
Specialised neurons located on brain side of blood brain barrier
Just beneath the ventral surface of the brainstem medulla
Very close to brainstem respiratory centres
How do central chemoreceptors sense changes in pCO2 and pH?
CO2 diffuses into brain ECF which bathes brain cells including central chemoreceptors neuron cells
CNS very limited HCO3- buffering capacity and therefore acidosis develops
What can lead to chronic hypercapnia?
Emphysematous COPD
What is hypercapnia?
Abnormally elevated CO2 levels in the blood
What happens if CO2 remains elevated?
pH of CSF/BECF slowly recovers over 8-24 hours because of choroid plexus increases active transport of HCO3 into CSF and BECF
