Chemoreceptors Flashcards
Where are central chemoreceptors located?
Ventro-lateral medulla
NTS
ventral respiratory group
locus coeruleus
caudal raphe
Retro Trapezoid nucleus
What is the composition of ECF giverened by?
Cerebrospinal fluid
Local blood flow
Local metabolism
What is CSF impermeable and permeable to?
Impermeable - H+ and HCO3-
Permeable - CO2
What do central chemoreceptors sense?
changes in pH and CO2
What happens when blood pCO2 rises?
Diffuses into CSF liberating H+ ions
How does CO2 level regulates ventilation?
By its effect on pH in CSF
Why is CSF pH lower than blood?
Contains less proteins so less buffer present eg Hb
What happens if PCO2 rises?
Diffuses into CSF -> releases H+ -> decreases pH -> chemoreceptor stimulated -> impulses to respiratory Centre -> increase in ventilation -> should lower pH
also cerebral vasodilation due to high CO2
What does chronic lung disease cause?
Increased CO2 retention which can lead to decreased pH in CSF
What is compensation for chronic lung diseas?
HCO3- lowers H+ ions to bring back pH to normal
accompanied by abnormally low ventilation
What is chronic lung disease and hypercapnia accompanied by?
Abnormally low ventilation
What happens when PCO2 goes down?
Less diffusion of CO2 into CSF -> less H+ ions formed -> pH increases -> chemoreceptors detect -> reduced impulses -> reduced ventilation
Leads to hypoventilation to increase PCO2 to restore pH
How long does the HCO3- compensatory response takes?
2-3 days
What do peripheral chemoreceptors respond to?
Elevations in PCO2
only 10-30% in response to hypercapnia but rapid
What happens to carotid body response to hypoxia?
Response is more robust/greater to PCO2
