Chemical Control Of Breathing Flashcards
What do we mean by Chemical control of breathing?
Chemoreceptors measure chemical parameters (of Arterial Blood/ Brain ECF) and send the information to respiratory centres in brainstem, in order to make appropriate adjustments to ventilation
What chemical parameters do Central and Peripheral Chemoreceptors monitor?
Central;
- H+ concentration
- pCO2
Peripheral;
- H+ concentration
- pCO2
- pO2
State the locations of the Peripheral Chemoreceptors and their Innervations
- Carotid bodies (CCA Bifurcation): Glossopharyngeal nerves
- Aortic bodies (In Aortic Arch): Vagus nerves
The Peripheral Chemoreceptors are located in Carotid Aortic Bodies.
Where are the Baroreceptors?
Carotid Sinus and Aortic Arch
What cells of the Carotid Body actually sense the chemical parameters
Type 1 Glomus cells
What does stimulation of the Peripheral Chemoreceptors do, to restore normal pO2?
Send signals to medulla to;
- Increase RR and Tidal Volume
- Direct more blood to brain, kidneys + increased pumping of blood by heart
Describe the Peripheral Chemoreceptors’ response to Carbon Dioxide
- Need large change in pCO2 to be stimulated
- Respond quickly to large pCO2 changes
Describe the Peripheral Chemoreceptors’ response to pH
- Carotid bodies are directly activates by changes in blood pH
- Low pH results in increased RR and Tidal Volume
How do CO2 levels affect sensitivity of Peripheral Chemoreceptors to pH and pO2?
Elevated pCO2= More sensitive to pH and pO2 changes
Briefly state how Central and Peripheral chemoreceptors differ?
Central;
- Are specialised neurons themselves
- Don’t sense pO2
Peripheral;
- Contain neuron-like cells (Type 1 Glomus cells)
- Do sense pO2
Where are the Central Chemoreceptors located?
What do they sense directly?
On ventral surface of medulla, exposed to Brain ECF
Brain ECF pH and pCO2
What separates the Brain ECF from the blood?
Describe this
What is in communication with brain ECF?
The Blood Brain Barrier
Allows free passage of CO2 but not HCO3- and H+
CSF (can be considered as same system)
Brain ECF pH is determined by its own ratio of HCO3:Dissolved CO2 (CO2 is determined by Plasma pCO2)
Why does brain ECF have limited buffering capacity?
Has no Hb/ other proteins
What determines HCO3 content of CSF (continuous with Brain ECF)
Choroid plexus cells which pump HCO3 into and out of CSF
In chronic hypercapnia, the cells adapt to pumping more HCO3 into CSF and this becomes the new normal
How are CSF and Brain ECF pCO2 affected by changes in arterial pCO2
If arterial pCO2 changes, then after a short delay pCO2 of Brain ECF and CSF will follow too
