Neural control of breathing

Question 1

What do CPG and RPG stand for

Answer 1

Central Pattern Generator
Respiratory Pattern Generator

Complex system of neurons within the medulla + pons, determines pattern of ventilation

Question 2

Why is it impossible to voluntarily asphyxiate onself

Answer 2

Urge to breath caused by excess CO2 overpowers, acute hypoxaemia results in loss of consciousness (body will breathe involuntarily)

Question 3

Describe pathway from CPG

Answer 3

Inspiratory/expiratory signals generated within CPG< signals to respiratory muscles via motor neurons.

Control of voluntary, emotional inputs as well as central and peripheral respiratory chemoreceptors

Question 4

Describe the role of the central respiratory chemoreceptors

Answer 4

Indirectly monitor changes in PaCO2, responds to changes in pH of cerebrospinal fluid. Arterial CO2 can pas through blood-brain barrier into the CSF, producing carbonic acid, and H+ activates CRCs. Urges ventilation/breathing

Question 5

Describe the role of the central respiratory chemoreceptors

Answer 5

Indirectly monitor changes in PaCO2, responds to changes in pH of cerebrospinal fluid. Arterial CO2 can pas through blood-brain barrier into the CSF, producing carbonic acid, and H+ activates CRCs. Urges ventilation/breathing

Question 6

Describe the role of peripheral chemoreceptors

Answer 6

Type-I glomus cells present within carotid and aortic bodies, which detect levels of O2, CO2 and pH within arterial blood.

Activated by low O2, high CO2, low pH

Signal to medullar centres to increase ventilation

Question 7

What is hypoxic drive

Answer 7

Increased ventilation in response to decreased PaO2, only occurs at very low PaO2

Question 8

How is hypoxic drive different in an individual with severe COPD

Answer 8

Patient unable to ventilate respiratory structures sufficiently. Chronic hypercapnia and hypoxia. CRC response reduced due to hypercapnia, because another homeostatic mechanism (helping to restore CSF pH) disrupts it. Ventilation further reduced, very low PaO2 and PO2.

Question 9

Causes of central breathing dysfunction

Answer 9

Inhibition the brainstem caused by drugs (opioids, barbiturates)
Injury to the brainstem caused by stroke or trauma
Congenital defects in brainstem signalling processes
Insufficient development of the relevant structures and pathways in neonates
Hypocapnia associated with altitude and hypobaric oxygen pressure

Question 10

What is central sleep apnoea

Answer 10

Temporary cessation of automated breathing during sleep, as pathways in breathing can no longer function.

Effects include episodes of breathing cessation, tiredness, cardiovascular complications and metabolic dysfunction