Control of Ventilation Flashcards
(46 cards)
What is eupnoea?
Normal breathing
What is apneusis?
Deep gasping inspiration and holding breath in then quick release
What does the pneumotaxic centre in the pons do?
Inhibits inspiratory phase
What does the apneustic centre in the pons do?
Prolongs inspiration
What are the 4 main respiratory nuclei in the medulla?
- Dorsal respiratory group (in nucleus tractus solitarius)
- Ventral respiratory group
- Pre-Botzinger complex
- Botzinger complex
Which respiratory nucleus is thought to be the key centre of respiratory rhythmogenesis?
pre-Botzinger complex
What kind of neurones does the dorsal respiratory group contain?
Inspiratory neurons
What kind of neurones does the ventral respiratory group contain?
Expiratory neurons
Where are the stretch receptors that affect breathing located?
Smooth muscle of the bronchial walls
What do the stretch receptors do to affect respiration?
Make inspiration shorter
Delay next respiratory cycle
(Negative feedback)
What is the name of the reflex where inflation of the lungs inhibits inspiration?
Hering-Breuer inflation reflex
Not in play in normal breathing but important in babies
What is the name of the reflex where deflation augments inspiration?
Deflation reflex
What do the juxtapulmonary receptors do?
In alveolar/bronchial walls, close to capillaries
Often activated in response to irritants or pulmonary embolism/oedema
Cause apnoea/rapid shallow breathing - cause breathlessness
What do the irritant receptors do?
Throughout airways between epithelial cells
Protective reflex - stops other irritants getting down
Which receptors are responsible for the deep breaths seen every 5-20 mins at rest preventing slow collapse of lungs during quiet breathing?
Irritant receptors
What do proprioceptive afferents do in the respiratory system?
Muscle spindles/Golgi tendon organs stimulated by change in length of muscles
Important for dealing with increased load and optimising tidal volume/frequency
How does pain receptor stimulation affect breathing?
Causes brief apnoea followed by increased breathing
Describe the ventilatory response to CO2 graph?
Linear relationship between alveolar PCO2 and ventilation up to a point then depression of respiratory centre - acidosis interferes with neural function (breathe less)
This depression also occurs in severe hypoxia
What happens at very low levels of CO2 on the ventilation graph?
Ventilation levels off
Never stop breathing all together
What is the relationship between PACO2 and alveolar ventilation ?
Inverse proportion
Halving ventilation rate doubles PACO2
What happens to the CO2 ventilation graph in metabolic alkalosis?
It shifts to the right (parallel straight line)
What happens to the CO2 ventilation graph in metabolic acidosis?
It shifts to the left (parallel straight line)
What does the ventilation pO2 graph look like?
Non linear
Ventilation only really increases when O2 conc is less than 8kPa
What is the significance of the 8kPa on the O2 ventilation graph?
Same pressure that Hb has reduced affinity for O2 - O2 comes off Hb at that pressure - breathe more at this point
