Chemical Control of Breathing

Question 1

Define hypoxia

Answer 1

Fall in pO2 in the tissues

Question 2

Define hypercapnia

Answer 2

Rise in pCO2

Question 3

Define hypocapnia

Answer 3

Fall in pCO2

Question 4

Define hyperventilation

Answer 4

Ventilation increase without change in metabolism

Question 5

Define hypoventilation

Answer 5

Ventilation decrease without change in metabolism

Question 6

Outline the effects of hyperventilation on plasma pH

Answer 6

pO2 will rise

pCO2 will fall

pH = rise

Question 7

Outline the effects of hypoventilation on plasma pH

Answer 7

pO2 will fall

pCO2 will rise

pH = fall

Question 8

Briefly outline the effects of acidic/alkali pH changes

Answer 8

Below 7 = enzymes denature

Above 7.6 = free [Ca] drops leading to tetany

Question 9

Define respiratory acidosis

Answer 9

Hypoventilation = increase in pCO2 = fall in plasma pH

Question 10

Define respiratory alkalosis

Answer 10

Hyperventilation = decrease in pCO2 = rise in plasma pH

Question 11

Define compensated respiratory acidosis

Answer 11

Respiratory acidosis compensated by the kidneys increasing [HCO3]

Question 12

Define compensated respiratory alkalosis

Answer 12

Respiratory alkalosis compensated by the kidneys decreasing [HCO3]

Question 13

Define metabolic acidosis

Answer 13

Tissue prod acid, reacts with HCO3 = fall in HCO3 = fall in pH

Question 14

Define metabolic alkalosis

Answer 14

High levels of HCO3 = rise in pH

Question 15

Define compensated metabolic acidosis

Answer 15

Metabolic acidosis compensated for by the lungs lowering pCO2

Question 16

Define compensated metabolic alkalosis

Answer 16

Metabolic alkalosis compensated for by the lungs raising pCO2

Question 17

How does ventilation change in response to falling inspired pO2?

Answer 17

Increased ventilation

Question 18

How does ventilation change in response to a fall in plasma pH

Answer 18

Increased ventilation

Question 19

Describe the location of the peripheral chemoreceptors

Answer 19

Carotid bodies in carotid sinus

Aortic bodies in aortic arch

Question 20

Describe the function of the peripheral chemoreceptors

Answer 20

Large fall in pO2 = increased breathing, increased HR, changes in blood flow distribution

Question 21

Describe the location of central chemoreceptors

Answer 21

Inside the medulla in the brain

Question 22

What is the function of central chemoreceptors

Answer 22

Very sensitive to pCO2

Selectively allows CO2 across the blood-brain barrier = acidification of CSF/ECF = stim central chemoreceptor neurons = stim breathing

Question 23

What is the carbonic acid-bicarb buffer system?

Answer 23

Buffer system in the blood

Dissolved CO2 = controlled by respiration

[HCO3] = controlled by the kidneys

Question 24

What is the choroid plexus?

Answer 24

Cell present in the CSF that have the ability to alter [HCO3] in CSF

Persisting hypoxia = initial ventilation increase will blow off CO2, pCO2 will then fall so choroid plexus will add H

Persisting hypercapnia = decreased CSF pH, choroid plexus adds HCO3