Control of Ventilation: Chemoreceptors Quiz

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Questions and Answers

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

Central and Peripheral Chemoreceptors.

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

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

Both central and peripheral chemoreceptors respond to changes in oxygen partial pressures.

False

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

PaO2 measures the amount of dissolved oxygen in plasma; CaO2 measures the total oxygen in the blood, including dissolved and hemoglobin bound. Signup and view all the answers

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

PaO2 measures the amount of oxygen dissolved in solution, not bound to hemoglobin. Signup and view all the answers

Do central or peripheral chemoreceptors respond to PaO2 levels?

Peripheral Signup and view all the answers

Between carotid and aortic body chemoreceptors, which ones are more sensitive to PaO2 levels?

Carotid bodies are more sensitive. Signup and view all the answers

How does the partial pressure of inspired oxygen affect the respiratory drive regarding carbon dioxide level and which chemoreceptors demonstrate this relationship?

Increasing the fraction of inspired oxygen will decrease the peripheral chemoreceptors' sensitivity to PaCO2 levels. Signup and view all the answers

If hydrogen ions and bicarbonate cannot pass the blood-brain barrier, how do central chemoreceptors monitor vascular PaCO2 levels?

Carbonic anhydrase converts H+ and bicarbonate into CO2, which diffuses across the BBB. Signup and view all the answers

Central chemoreceptors directly respond to changes in pH and carbon dioxide levels in the CSF.

True Signup and view all the answers

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

CSF has a smaller concentration of proteins, which normally act as buffers. Signup and view all the answers

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

At about 60 mmHg. Signup and view all the answers

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

About 7.3. Signup and view all the answers

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

About 7.4. Signup and view all the answers

Is respiratory drive via central chemoreceptors more responsive to pH or carbon dioxide levels?

False Signup and view all the answers

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

Peripheral chemoreceptors sense and respond to acute PCO2 changes; Central chemoreceptors sense and respond to long-term PCO2 changes. Signup and view all the answers

Study Notes

Chemoreceptors and Ventilation Control

Chemoreceptors are classified into two types: Central and Peripheral, affecting ventilation regulation.
Central chemoreceptors are located in the Medulla, while Peripheral chemoreceptors are found in the Aortic arch and Carotid Sinus.

Response to Partial Pressures

Central chemoreceptors only respond to pH and CO2 levels, not to changes in oxygen partial pressures.
Arterial partial pressure of oxygen (PaO2) indicates the oxygen dissolved in plasma, based on Henry's Law, while arterial concentration of oxygen (CaO2) includes both dissolved oxygen and oxygen bound to hemoglobin.

Implications of CO Poisoning

In carbon monoxide poisoning, PaO2 levels may appear normal because PaO2 measures dissolved oxygen, unaffected by CO binding to hemoglobin, which impairs the ability to deliver oxygen effectively.

Sensitivity and Function of Chemoreceptors

Peripheral chemoreceptors respond to PaO2 levels, with Carotid bodies being more sensitive to changes compared to Aortic bodies.
Increased inspired oxygen fraction decreases peripheral chemoreceptor sensitivity to carbon dioxide (PaCO2), resulting in reduced ventilatory drive for a given PaCO2.

Monitoring CO2 Levels in the Central Nervous System

Central chemoreceptors can monitor arterial PaCO2 levels despite H+ ions and bicarbonate not passing the blood-brain barrier due to carbonic anhydrase converting these substances back into CO2, which can diffuse across.
Central chemoreceptors directly react to changes in pH and CO2 concentrations in cerebrospinal fluid (CSF).

pH Variations in Blood and CSF

Identical PCO2 levels in arteries and CSF lead to a lower pH in CSF because it contains fewer proteins to buffer pH changes compared to blood.

Ventilatory Drive Triggers

A rapid increase in ventilatory drive via peripheral chemoreceptors begins at a PaO2 of about 60 mmHg.
The average pH of cerebral spinal fluid in a healthy adult at rest is around 7.3, while the average blood pH is about 7.4.

Responsiveness of Chemoreceptors

Central chemoreceptors are more responsive to carbon dioxide levels than to pH levels.
Peripheral chemoreceptors detect acute changes in PCO2, while central chemoreceptors monitor long-term PCO2 alterations.

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Description

Test your knowledge on the control of ventilation through chemoreceptors. This quiz covers the classifications, locations, and functions of central and peripheral chemoreceptors. Engage with flashcards to better understand the physiological mechanisms of breathing control.