Acid-Base in the Control of Ventilation Flashcards
What are the three components that are involved in the control of ventilation?
A central controller, sensors and effeects
What three types of receptors does the respiratory control system have?
Central and peripheral chemoreceptors and peripheral mechanoreceptors
What do central chemoreceptors detect?
CO2, specifically hypercapnia in the CSF they bathe in (within the medulla oblongata) as a result of increased acidity of the CSF
Where are the central chemoreceptors, involved in control of ventilation, found?
Specialised neurones located neurones in the ventral surface of the medulla oblongata
What is the normal pH of CSF?
7.32
Why does the CSF have a far weaker buffering capacity than the blood?
Because no plasma proteins are filtered through the choroid plexus, the CSF contains almost no protein
What stimulates most of the urge to breathe?
Drive from the central chemoreceptors in the medulla oblongata
Describe the role of the central chemoreceptors in the control of ventilation
Specialised neurones in medulla oblongata, which detect hypercapnia (as a result of increased acidity in the CSF) –> activates chemoreceptors –> stimulate neurones in the respiratory centres in the medulla –> increased ventilation rate
How can central chemoreceptors detect hypercapnia due to an increased acidity?
Carbon dioxide diffuses freely through the BBB into the CSF where it reacts with water to form carbonic acid which is then converted to protons and bicarbonate via carbonic anhydrase.
Why do central chemoreceptors become desensitised in chronic pulmonary disease?
There are chronically high CO2 levels in the blood, and therefore the central chemoreceptors gradually become less sensitive to this stimuli and therefore the drive for ventilation from CO2 (hypercapnia) is diminished
Where are the peripheral chemoreceptors, involved in control of ventilation, found?
In the carotid bodies at the bifurcation of the common carotid arteries and in the aortic bodies above and below the aortic arch.
What does the carotid body contain?
Most heavily vascularised tissue in the human body
What do peripheral chemoreceptors detect?
Mainly to reduced pO2 and plasma pH (acidity caused by hypercapnia) and less so to raised pCO2 directly
Describe the afferents from the peripheral chemoreceptors
Afferents from the chemoreceptors travel mainly in the glossopharyngeal and vagus nerves to the brainstem
What cells make up the carotid body?
Glomus cells