Control of ventilation Flashcards
What are the respiratory nuclei in the medulla which control breathing?
The DRG (dorsal respiratory group) in the NTS (nucleus tractus solitarus) The PBC (pre-Bötzinger complex) and the BC (Bötzinger complex) near the RFN nucleus retrofacialis
Describe the DRG
found in the NTS (nucleus tractus solitarus) has a ramp like activity (increases slowly then decreases rapidly) controls the depth and rate of breathing. Neural activity relayed to phrenic nerves.
DRG inhibitory neurones inhibit expiratory neurones.
What factors can cause higher centres to act on the pons to modulate breathing?
Temperature
Emotion (anxiety)
What receptors in the lung modulate breathing?
Irritant receptors
proprioceptors
stretch
juxtapulmonary receptors
What is the Herring-Brever inflation reflex?
Inflation of the lung inhibits inspiration
What is the deflation reflex?
deflation augments inhalation (primes for next breath)
Where are stretch receptors found in the lungs?
Smooth muscle of the bronchial walls
Where are juxtapulmonary receptors found?
In the alveolar/bronchial walls near capillaries
What do juxtapulmonary receptors cause?
Apneoa/rapid shallow breathing/laryngeal constriction in response to:
increased alveolar wall fluid, oedema, pulmonary congestion etc.
Where are irritant receptors found?
All through the airways, but in trachea they cause cough; and in the lower airways it causes hypernoea.
What is responsible for the sneeze reflex?
Nasal trigeminal nerve
Why are the effects of hypoxia and hypercapnia said to be synergistic?
They have the same effect: increased ventilation.
Where are chemosensitive area in the medulla oblongata?
ventrolateral surface of the medulla near the exit of CIX and CX
Why are pulmonary chemoreceptors in the brain so sensitive to changes in CO2?
There is very little protein in the interstitial space in which the chemoreceptors are found so there is no buffering so there is a relatively large change in pH for a small change in CO2 conc.
What occurs in central pulmonary chemoreceptors which leads to chronic respiratory disease?
Prolonged hypercapnia leads to adaptation of central chemoreceptors. Initially hypercapnia leads to increased ventilation (due to increased pH) eventually the pH normalises even though there is still hypercapnia so ventilative drive decreases even though it shouldn’t.
