Respiratory Control of Ventilation

Question 1

What provides chief baseline control of respiration?

Answer 1

Brainstem “pacemakers”

Question 2

What are the chief inputs to the brainstem “pacemakers”?

Answer 2

• pH in the cerebrospinal fluid
• Pco2 in the periphery
• Po2 in the periphery
• pH in the periphery

Question 3

What do medullary pH sensors monitor?

Answer 3

Arterial Pco2

Question 4

How do medullary pH sensors monitor arterial Pco2?

Answer 4

By Pco2’s influence on CSF acidity (carbonic anhydrase).

Question 5

What senses Pco2?

Answer 5

Carotid and aortic bodies

Question 6

What senses Po2?

Answer 6

Carotid bodies

Question 7

What senses arterial pH?

Answer 7

Carotid bodies

Question 8

What can cause an increase in breathing?

Answer 8

High Pco2 or low Po2/pH.

Question 9

What variable is most relevant for day-to-day control of ventilation?

Answer 9

CO2

Question 10

What is important in altitude adaptations and in chronic lung disease?

Answer 10

O2

Question 11

What is the mechanism of exercise-induced hyperventilation?

Answer 11

Unknown

Question 12

What are three major feedback mechanisms for control of ventilation?

Answer 12

1. Central controller
2. Peripheral sensors (chemoreceptors)
3. Efferent mechanisms (nerves and muscles)

Question 13

Where is the central controller?

Answer 13

Brainstem (pons and medulla)

Question 14

What can panic attacks do to the Pco2?

Answer 14

They can halve the Pco2 as a result of doubling the respiration rate!

Question 15

What is the most important sensor in day-to-day regulation of ventilation?

Answer 15

Central chemoreceptors

–> they respond to pH

Question 16

What are the peripheral chemoreceptors and what do they respond to?

Answer 16

Aortic arch and Carotid bodies.

-Respond to Pco2, pH and Po2

Question 17

What are the lung receptors?

Answer 17

• Stretch receptors
• Irritant receptors
• J receptors
• Bronchial receptors

Question 18

How do Central pH receptors relate to respiration?

Answer 18

• H+ stimulates respiration

- Alkalosis suppresses respiration

Question 19

What surrounds Central pH receptors and what determines the pH there?

Answer 19

Bathed by cerebrospinal fluid (CSF)

• H+ cannot cross the BBB
• CO2 diffuses across and is converted to carbonic acid

Question 20

What determines CSF pH? What is the normal CSF pH?

Answer 20

Plasma CO2, 7.32

Question 21

How is CSF acidosis compensated for?

Answer 21

By HCO3 retention by the CSF
–>Can be observed in patients with emphysema having extremely low Po2 and high Pco2 and relatively low respiration rates because of this compensation