Control of Respiration

Question 1

What would PaO2, SaO2, PaCO2, and A-a gradient do with low [Hb]?

Answer 1

they would all stay normal

Question 2

What would PaO2, SaO2, PaCO2, and A-a gradient do with carbon monoxide poisoning?

Answer 2

all normal except SaO2 would decrease

Question 3

Where is the respiratory center located?

Answer 3

the medulla

Question 4

What does the output from the medulla control?

Answer 4

• motor neurons that control respiratory muscles
• changes in tidal volume
• changes in breathing rate

Question 5

Where are peripheral chemoreceptors located?

Answer 5

the carotid bodies

Question 6

What is the function of peripheral chemoreceptors?

Answer 6

increase ventilation in response to:

• decreased arterial O2
• increased arterial PCO2
• high arterial [H+]

Question 7

Which type of receptors respond to changes in pH/[PaCO2] the fastest?

Answer 7

peripheral chemoreceptors

Question 8

Where are central chemoreceptors located and what type of receptor is it?

Answer 8

located on the ventral surface of the medulla, H+ receptor

Question 9

Where do the H+ ions come from that the central chemoreceptors sense?

Answer 9

CO2 crosses the BBB and causes bicarbonate formation and the release of H+ ions. Therefore, the H+ ions DO NOT come from the blood but instead from HCO3 in the brain from CO2 crossing the BBB

Question 10

T/F the CSF has a high buffering capacity

Answer 10

False, it has a low buffering capacity

Question 11

What is the most important day to day regulator of ventilation?

Answer 11

central chemoreceptors

Question 12

What type of receptor mediates increase in ventilation when climbing Mt. Everest?

Answer 12

peripheral O2 receptors

Question 13

What type of receptor mediates increase in ventilation with ketoacidosis?

Answer 13

peripheral proton receptors

Question 14

What type of receptor mediates increase in ventilation when climbing stairs?

Answer 14

peripheral CO2 receptors

Question 15

What type of receptor mediates increase in ventilation with bronchitis?

Answer 15

central proton receptors/CO2 sensors

Question 16

what elements of blood in bronchitis could potentially mediate increase in ventilation?

Answer 16

CO2

Question 17

Why are protons and O2 not major mediators of ventilation?

Answer 17

because H+ are buffered well in the blood and oxygen receptors are not very sensitive

Question 18

Why is the initial recovery of PaO2 at high altitude incomplete?

Answer 18

• initially reduced CO2 leads to reduced H+ in the blood
• this leads to respiratory alkalosis due to decreased PCO2
• compensation: decrease in bicarb through reabsorption in kidney
• this leads to decreased [HCO3-] in the blood
• this creates a gradient of HCO3 from CSF to blood causing flow of HCO3 from the CSF to the blood
• this increases the [H+] in the CSF because HCO3 leaves (dilution)
• central chemoreceptors sense increased [H+] which results in increased ventilation turning it into a vicious cycle with more loss of CO2