Resp. 5 - Control of Ventilation Flashcards
Respiratory Control System
- Automatic Rhythm
- Rhythm Adjustment to Changing Demands
– E.g. – metabolic demands ( PO2 , PCO2 and pH)
Automatic rhythm used when were not consciously controlling breathing, in tune with
metabolic demands (partial pressure of O2 and CO2 and pH) that will increase or decrease ventilation or the depth of breathing or the rate.
Change in partial pressures are monitored by:
- Peripheral Chemoreceptors (PCR)
- Central Chemoreceptors (CCR)
-Drive the CPG (central pattern generator)
What does the CPG do?
Increase or decrease ventilation
Respiratory and Metabolic Acidosis/Alkalosis:
- Respiratory acidosis →
- Respiratory alkalosis →
- Metabolic Acidosis →
- Metabolic Alkalosis →
• Respiratory acidosis →
hypoventilation (CO2 production > CO2 elimination): not only PCO2 ↑ but also H+ concentration ↑
• Respiratory alkalosis →
hyperventilation (CO2 production < CO2 elimination): not only PCO2 ↓ but also H+ concentration ↓
• Metabolic Acidosis →
↑ in blood H+ concentration independent from changes in PCO2
• Metabolic Alkalosis →
↓ in blood H+ concentration independent from changes in PCO2
Where are peripheral chemoreceptors located
Carotid and aortic bodies
Peripheral Chemoreceptor Sense mostly changes in
arterial PO2 and will also be activated by changes in pH (H+ conc.).
• The carotid and aortic bodies sense primarily
hypoxia, which is a low arterial PO2 level
Which cells are coupled with blood vessels to monster the levels of O2 levels
The Glomus Cell Is the Chemosensor in the Carotid and Aortic Bodies
_______ that are responsible for evoking an increase in ventilation to a decrease in PaO2.
Glomus cells
Type I glomus cells -
chemosensitive; drive the response, or the change in ventilation, if there are changes in the arterial PO2.
- Triggered when O2 falls below 60 mmHg.
- sensitive to high conc. of H+ (low pH)
Chemical Control of Ventilation- CCR
- Sensitivity to increase in PaCO2(H+)
* Indirectly does sensitive to PaCO2, and directly sensitive to H+ levels.
Respiratory Acidosis vs Metabolic Acidosis
Both result in significant responses when viewed by CCR
Respiratory Acidosis: increase in PaCO2 and decrease in pH
Metabolic Acidosis: no change in PaCO2 but decrease in pH
Metabolic acidosis Occurs with the production of
acids which are carried in the blood and are not associated with changes in PCO2
Metabolic acidosis process
concentration of H+ → activation of PCR (glomus cells in carotid bodies) → increase ventilation → decrease alveolar PCO2 → decrease arterial PCO2 → return of arterial hydrogen ions towards normal levels
• H+ stimulates mostly peripheral chemoreceptors because
H+ does not cross easily blood brain barrier (As CO2 does)
Respiratory acidosis process
As CO2 crosses the BBB, producing more bicarbonate and H+, the pH will drop making it more acidic, the CCR then respond by increasing ventilation.
Dependence of CSF pH on blood pH
- the response for repository acid-base changes is far greater then metabolic acid-base changes because of the H+ easily detected by CCR.
- the reps once for Metabolic acid-base changes is a lot smaller since H+ aren’t diffusible, and wont be detected (small relative change)
Dependance of ventilation on CSF pH
Heavily relies on the CCR to monitor pH and increase ventilation when its to acidic.
Very importantly for control of metabolism, or acidity of blood. Chngaes in CO2 and H+ on a regulatory pathways are
more important then any changes in O2.
