Neural control of breathing

Question 1

What determines the basic pattern of ventilation

Answer 1

Central pattern generator (CPG) - sometimes referred to as the ‘respiratory pattern generator’

Question 2

What are the 2 opposing groups of respiratory neurons that signal to initiate inspiration of expiration

Answer 2

Dorsal respiratory group - inspiration

Ventral respiratory group - expiration

Question 3

What does dorsal respiratory group initiate/stimulate

Answer 3

INSPIRATION

Stimulate diaphragm and external intercostals

Question 4

What does ventral respiratory group initiate/stimulate

Answer 4

EXPIRATION

Stimulate abdominal muscles and internal intercostals

Question 5

Central pattern generator

Answer 5

Determines rate and depth of ventilation

Receives inputs from central and peripheral chemoreceptors

Question 6

Central respiratory chemoreceptors (CRC)

Answer 6

Locates within the medulla

Indirectly monitor changes in PaCO2

Question 7

How does central respiratory chemoreceptors monitor PaCO2

Answer 7

• Increase in PaCO2 will decrease blood pH within arterial blood. But it can’t pass through blood brain barrier
• But arterial CO2 can pass through the blood brain barrier into cerebrospinal fluid
• The CO2 will react and produce HCO3- and H+.
• The H+ activate CRCs

Question 8

Peripheral chemoreceptors

Answer 8

Consist of type I glomus cells found in carotid and aortic bodies
Detect levels of O2, CO2 and pH within arterial blood

Question 9

What activates peripheral chemoreceptors

Answer 9

Low O2
High CO2
Low pH
They sidnal to medullar centres to increase ventilation

Question 10

What other inputs are there for CPG

Answer 10

Stretch receptors within the lungs
Prevent damage due to over inflation
Irritant receptors within the airways that initiate cough

Question 11

Pathologies affecting the initiation of breathing

Answer 11

• Inhibition of the brainstem caused by drugs such as opiods
• Injury to brainstem
• Congenital defects in brainstem signalling processes (central hypoventilation syndrome, lack capacity to breathe whilst asleep)
• Insufficient development of relevant structures and pathways in neonates (infantile central sleep apnoea)