Control of Ventilation: Chemoreceptors and Chemical Reflexes.

During a resting metabolic state, at what PaO2 do you begin to see a rapid increase in peripheral chemoreceptor induced ventilatory drive?

At about 60 mmHg

True or False. Both Central and Peripheral Chemoreceptors respond to changes in Oxygen Partial Pressures?

False. Central chemoreceptors only respond to changes in pH and CO2 partial pressures.

In a healthy adult at rest, what is the average pH of their cerebral spinal fluid?

About 7.3

In a healthy adult at rest, what is the average pH of their blood?

About 7.4

Is respiratory drive via central chemoreceptors more responsive to pH or Carbon Dioxide levels?

Carbon Dioxide Levels.

If Hydrogen ions and Bicarbonate cannot pass the blood brain barrier, how is it that the central chemoreceptors located in the medulla can monitor vascular PaCO2 levels?

Carbonic anhydrase converts H+ and bicarbonate back into CO2 which diffuses across the BBB where it is converted back into H+ and bicarbonate.

Between Carotid and Aortic body chemoreceptors, which ones are more sensitive to PaO2 levels?

Carotid bodies are more sensitive.

Where are the central and peripheral chemoreceptors located in the body?

Central Chemoreceptors: Located in the Medulla. Peripheral Chemoreceptors: Aortic arch and Carotid Sinus.

What are the two categories of Chemoreceptors that influence ventilation control with regards to their location?

Central and Peripheral Chemoreceptors.

If the PCO2 levels in the arteries and the CSF are identical, then why does the CSF have a lower pH?

Compared to blood, CSF has a smaller concentration of proteins which act to buffer changes in pH. Therefore, the same PCO2 in the CSF will result in a lower pH.

How does the partial pressure of inspired oxygen effect the respiratory drive with regards to carbon dioxide level and which chemoreceptors demonstrate this relationship?

Increasing the fraction of inspired oxygen will decrease the peripheral chemoreceptors sensitivity to PaCO2 levels. This will result in decreased ventilatory drive for a given PaCO2.

In a patient with CO poisoning, why does their PaO2 levels appear normal?

PaO2 measures the amount of oxygen dissolved in solution, not bound to hemoglobin. Carbon monoxide binds to hemoglobin and therefore will not effect the dissolved oxygen content.

What is the difference between Arterial partial pressure of oxygen [PO2] and arterial concentration of oxygen [CaO2]?

PaO2: Is a measure of the amount of dissolved oxygen in plasma as calculated by Henry's Law of Solubility. CaO2: Is a measure of the total oxygen in the blood to include dissolved and hemoglobin bound.

Do central or peripheral chemoreceptors respond to PaO2 levels?

Peripheral

Which chemoreceptors detect and respond to acute changes to PCO2 and which ones respond to long term PCO2 changes?

Peripheral CR's sense and respond to acute PCO2 changes. Central CR's sense and respond to long term PCO2 changes.

True or False. Central chemoreceptors directly respond to changes in pH and Carbon Dioxide levels in the CSF?

True. CCR's are directly stimulated CO2 and by changes in pH that result from carbonic anhydrase action.