Chemical Control of Breathing Flashcards
Define hypoxia
Fall in pO2 in the tissues
Define hypercapnia
Rise in pCO2
Define hypocapnia
Fall in pCO2
Define hyperventilation
Ventilation increase without change in metabolism
Define hypoventilation
Ventilation decrease without change in metabolism
Outline the effects of hyperventilation on plasma pH
pO2 will rise
pCO2 will fall
pH = rise
Outline the effects of hypoventilation on plasma pH
pO2 will fall
pCO2 will rise
pH = fall
Briefly outline the effects of acidic/alkali pH changes
Below 7 = enzymes denature
Above 7.6 = free [Ca] drops leading to tetany
Define respiratory acidosis
Hypoventilation = increase in pCO2 = fall in plasma pH
Define respiratory alkalosis
Hyperventilation = decrease in pCO2 = rise in plasma pH
Define compensated respiratory acidosis
Respiratory acidosis compensated by the kidneys increasing [HCO3]
Define compensated respiratory alkalosis
Respiratory alkalosis compensated by the kidneys decreasing [HCO3]
Define metabolic acidosis
Tissue prod acid, reacts with HCO3 = fall in HCO3 = fall in pH
Define metabolic alkalosis
High levels of HCO3 = rise in pH
Define compensated metabolic acidosis
Metabolic acidosis compensated for by the lungs lowering pCO2
Define compensated metabolic alkalosis
Metabolic alkalosis compensated for by the lungs raising pCO2
How does ventilation change in response to falling inspired pO2?
Increased ventilation
How does ventilation change in response to a fall in plasma pH
Increased ventilation
Describe the location of the peripheral chemoreceptors
Carotid bodies in carotid sinus
Aortic bodies in aortic arch
Describe the function of the peripheral chemoreceptors
Large fall in pO2 = increased breathing, increased HR, changes in blood flow distribution
Describe the location of central chemoreceptors
Inside the medulla in the brain
What is the function of central chemoreceptors
Very sensitive to pCO2
Selectively allows CO2 across the blood-brain barrier = acidification of CSF/ECF = stim central chemoreceptor neurons = stim breathing
What is the carbonic acid-bicarb buffer system?
Buffer system in the blood
Dissolved CO2 = controlled by respiration
[HCO3] = controlled by the kidneys
What is the choroid plexus?
Cell present in the CSF that have the ability to alter [HCO3] in CSF
Persisting hypoxia = initial ventilation increase will blow off CO2, pCO2 will then fall so choroid plexus will add H
Persisting hypercapnia = decreased CSF pH, choroid plexus adds HCO3
