Lecture 8-Chemical Control of Breathing

Question 1

Define hypoxia

Answer 1

Fall in pO2

Question 2

Define hypercapnia

Answer 2

Rise in pCO2

Question 3

Define hypocapnia

Answer 3

Fall in pCO2

Question 4

Define hyperventilation

Answer 4

Increased ventilation without change in metabolism - increased pO2 and decreased pCO2

Question 5

Define hypoventilation

Answer 5

Decreased ventilation without change in metabolism - decreased pO2 and increased pCO2

Question 6

How does hyperventilation affect pH?

Answer 6

Decreases pCO2 -> rise in pH

Question 7

How does hypoventilation affect pH?

Answer 7

Increases pCO2 -> fall in pH

Question 8

What are the acute effects on ventilation of a falling inspired pO2?

Answer 8

• increased breathing

- changes in HR and blood flow distribution

Question 9

What are the acute effects on ventilation of increases in inspired pCO2?

Answer 9

Increase ventilation

Question 10

Where are peripheral chemoreceptors found?

Answer 10

Carotid and aortic bodies

Question 11

True or false: peripheral chemoreceptors are sensitive to changes in pCO2

Answer 11

FALSE

Question 12

Where are central chemoreceptors found?

Answer 12

Medulla of the brain

Question 13

What do central chemoreceptors do?

Answer 13

Respond to changes in pH of CSF

Question 14

What is the CSF [HCO3-] controlled by?

Answer 14

Choroid plexus cells

Question 15

What corrects persisting changes in CSF pH?

Answer 15

Choroid plexus cells which change [HCO3-]

Question 16

Describe the effect of persisting hypoxia on the CSF

Answer 16

• hypoxia detected by peripheral chemoreceptors to increase ventilation but pCO2 will fall and ventilation will then decrease
• CSF choroid plexus cells add H+ or HCO3- into CSF and central chemoreceptors accept this pCO2 as normal

Question 17

Describe the effect of persisting hypercapnia on the CSF

Answer 17

• peripheral and central chemoreceptors stimulate breathing but acidic pH is undesirable for neurons
• choroid plexus cells need to adjust pH of CSF by adding HCO3- and central chemoreceptors will accept this high pCO2 as normal