Control of Ventilation

Question 1

Respiratory Centres: Location

Answer 1

Pons and medulla

Question 2

Respiratory Centres: Function

Answer 2

Sets automatic rhythm of breathing

• Co-ordinates firing of smooth and repetitive bursts of APs in DRG
• APs travel to the inspiratory muscles via the phrenic and intercostal nerves

Question 3

Respiratory Centres: Stimuli altering respiratory drive, rate and depth of breathing (4)

Answer 3

1. Emotion via limbic system
2. Voluntary over-ride via descending pathways from cerebral cortex (higher centres)
3. Mechano-sensory input from the thorax e.g. stretch reflex
4. Chemical composition of the blood detected by chemoreceptors

Question 4

Respiration and swallowing

Answer 4

• Inhibited to avoid aspiration

- Followed by expiration to dislodge glottic particles

Question 5

Central chemoreceptors: Location

Answer 5

Medulla

- Primary ventilatory drive

Question 6

Central chemoreceptors: Function

Answer 6

• Respond to PCO2 (indirectly through [H+] in CSF as)
  1. CSF [H+] increase
  2. Feedback to Respiratory Centres
  3. Increased ventilation

Question 7

CO2 dissociation equation

Answer 7

CO2 + H2O H2CO3 H+ + HCO3-

Question 8

Peripheral chemoreceptors: Location

Answer 8

Aortic and carotid sinus

- Secondary ventilatory drive

Question 9

Peripheral chemoreceptors: Function

Answer 9

Respond directly to
- [H+] (reflects pH and PCO2) - PaO2.
Important in hypoxia and acid-base imbalance

Question 10

Signal pathway for low PaO2

Answer 10

1. Low PO2
2. No oxygen combined with oxygen sensor
3. KO2 channel closes
4. Decreased K+ permeability
5. Cell depolarises
6. Exocytosis of dopamine-containing vesicles
7. Dopamine binds to receptor on sensory neuron
8. Action potential (signal) to medullary centres
9. Ventilation increased

Question 11

Respiratory response to acidosis

Answer 11

Increases ventilation

Question 12

Respiratory response to alkalosis

Answer 12

Decreases ventilation