Respiratory Physiology 5 Flashcards
Which nerve controls the diaphragm?
Phrenic nerve
What nerves control the external intercostal muscles?
Intercostal nerves.
Where are the nervous respiratory centres situated?
pons and medulla
What is the spinal root of the phrenic nerve?
C3-C5
What modulates the rhythm of resp centres?
Emotion, voluntary override, mechano-sensory input from thorax, chemical composition of the blood detected by chemoreceptors
What do the central chemoreceptors do?
-detect changes in hydrogen ion conc in CSF
-cause reflex stimulation of ventilation follwing rise in [H+]
What is hypoxic drive?
When patients become desensitised to high PCO2 due to chronic lung disease and instead rely on changes in PaO2 to stimulate ventilation.
Where are the peripheral chemoreceptors?
carotid and aortic bodies
What do peripheral chemoreceptors do?
Detect changes in arterial PO2 and [H+]
Cause reflex stimulation of ventilation following significant fall in arterial PO2
What drugs can depress resp centres?
Barbiturates and opioids
Why is nitrous oxide dangerous to use in patients with chronic lung disease?
Blunts peripheral chemoreceptor response to falling PaO2 reducing hypoxic drive
What happens if plasma pH falls ([H+] increases)
Ventilation will be stimulated (acidosis)
Opposite if pH increases (alkalosis)
To what extent can ventilation be controlled voluntarily?
To some extent but chemical control mechanisms cannot be overriden.
