Control of ventilation Flashcards
What nerves if severed will lead to breathing being stopped?
Phrenic nerve origin
C3 to C5
Where are the respiratory centres in the brain?
Pons and medulla
Where does the phrenic nerve innervate?
the diaphragm
Where does the intercostal nerve innervate?
External intercostal muscles
Dorsal respiratory group
Primarily muscles of inspiration
Ventral respiratory group
Output to expiratory and some inspiratory
What 3 structures do the VRG target? Why?
Larynx, pharynx and tongue muscles - to keep muscular tone and patency
What 4 things modulate the rhythm of respiratory centres?
- Emotion
- voluntary over ride
- mechano receptor input from thorax
- chemical composition of blood
What is the most significant modulator of the respiratory centres?
Chemoreceptors detecting change in the chemical composition of the blood
Central chemoreceptors - where?
Medulla
What do central chemoreceptors respond to?
Directly to H+ which reflects the CO2
Which type is the primary ventilatory drive?
Central chemoreceptors
Where is the changes detected by central chemoreceptors detected?
CSF around the brain
What is hypercapnia?
Raised PCO2
Do central chemoreceptors respond directly to change in {H+} change?
No
Does CO2 or hydrogen cross the blood brain barrier?
CO2
What does an increase in hydrogen do to breathing?
Increase PaCO2 which leads to reflex stimulation and leads to hyperventilation
What are the peripheral chemoreceptors?
Carotid and aortic bodies
What do peripheral chemoreceptors respond to?
Primarily to plasma [H+] and PaO2
When is there a reflex stimulation of ventilation?
Rise in [H+] or fall in PaO2
Do peripheral chemoreceptors respond to Pa02 or oxygen content?
Pa02
Suggest a scenario which would lead to increased plasma pH
Vomiting
What leads to a large degree of voluntary control over breathing?
Descending neural pathways from cerebral cortex -> respiratory motor neurons
Barbiturates and opioids
Depress respiratory centres and overdose leads to respiratory fail
