Control of Breathing

Question 1

Describe the automatic control of breathing

Answer 1

Phrenic nerve sends impulses to respiratory centre in pons/medulla to send efferents to effectors (diaphragm and pharynx) to control respiration

Question 2

How is control of breathing affected by low pH?

Answer 2

Low pH = acidosis = raised CO2

Hypoventilation

Question 3

How is control of breathing affected by low PaO2?

Answer 3

Hyperventilation restores hypoxia

Question 4

What are peripheral chemoreceptors?

Answer 4

Carotid bodies send impulses via CN IX to respiratory centre in pons/medulla to increase ventilation rate

Question 5

What are central chemoreceptors and how do they control respiration?

Answer 5

Central chemoreceptors detect pH changes in CSF as a surrogate for arterial blood (pCO2 is the same).

Chemoreceptors are key to respiratory compensation: will control respiration to have opposite effect. Eg if CSF pH is raised and body in metabolic alkalosis, then central chemoreceptors will stimulate respiratory centre to hyperventilate resulting in compensatory respiratory acidosis.

Question 6

Where are central chemoreceptors located?

Answer 6

On surface of medulla so in direct contact with CSF (secreted by choroid plexus, pH determined by HCO3- and CO2)

Question 7

Physiological response to hypoxia?

Answer 7

Hyperventilation to take in more O2 and restore PAO2 for O2 delivery to tissues

Question 8

Physiological response to hypercapnia?

Answer 8

Hypercapnia = raised blood CO2

Question 9

If someone goes into a respiratory arrest, which part of the brain is most likely affected?

Answer 9

Medulla