Chemical control of ventilation Flashcards
What do chemoreceptors detect
Changes in arterial;
- pCO2
- pO2
- [H+]
does oxygenated blood have more [H+] or deoxygenated
oxygenated
Where are central chemoreceptors found
Medulla
What are central chemoreceptors sensitive to
Changes in;
[H+] and pCO2
Where are peripheral chemoreceptors found
Within aortic arch and carrot arteries
What are peripheral chemoreceptors sensitive to
Changes in;
arterial pO2 and pH
How are CCRs (central chemoreceptors) activated
- Blood brain barrier impermeable to H+ and HCO3- but permeable to CO2
- Increase in partial pressure of CO2 causes it to diffuse out of the blood vessel
- H+ ions are formed from a reaction
- Increase in the concentration of H+ in extracellular fluid and cerebrospinal fluid is detected by central chemoreceptors and leads to hyperventilation
- Hyperventilation decreases PCo2 in blood and cerebral spinal fluid
- decreases in PCO2 leads o hyperventilation
What does a decreased arterial O2 do in peripheral chemoreceptors
Hyperventilation
-stimulated when arterial pO2 falls below a certain level
What does an increase in PCO2 mean in peripheral chemoreceptors
Not as important as CCR
Where is a fall in pH detected
By carotid peripheral chemoreceptors but not aortic bodies
what does hypoventilation cause
Respiratory acidosis
What does hyperventilation cause
Hyperventilation
What is increased in hypoventilation
[H+] excretion
[HCo3-] reabsorption
In kidneys
What is increased in hyperventilation
[H+] reabsorption
[HCo3-] excretion
in kidneys
How does diabetes affect ventilation
In uncontrolled diabetes, there is a decrease in the ability of kidneys to excrete H+ and reabsorb HCO3-
To compensate, there is an increase in ventilation which leads to a decrease in arterial partial pressure of CO2
What is the order of importance in ventilation stimulus
1) PCO2
2) pH
3) PO2
What receptors are the most sensitive to changes in PCO2
central chemoreceptors
Why control PCO2?
Avoid acid-base problems
What does a decrease in pH cause
An increase in ventilation
What detects the most changes of PO2
Peripheral chemoreceptors
When are PCRs stimulated when PO2 levels drop
Below 13.3kPa
Why control PO2?
to avoid hypoxia
