L8 - Acid Base Balance - Pt 2 - Chemoreceptors & the Lungs Flashcards
What 3 things control the blood gas composition?
Partial pressure of Oxygen
Partial pressure of Carbon Dioxide
Partial pressure of hydrogen
How is the blood gas compositon maintained?
By Peripheral and Central chemoreceptors (negative feedback system)
What 3 conditions increase ventilation?
Hypoxia - decrase in oxygen levels
Hypercapnia - increase in CO2 levels
Acidosis - Inccrease in H+ levels (acidity)
Where are the peripheral chemoreceptors found?
carotid and Aortic bodies
Where do the peripheral chemorecpetors signal?
The sinus nerve, the vagus nerve and the glossopharyngeal nerve
What is the main stimulus for peripheral chemoreceptors?
Hypoxia (fall in PO2)
What is the main cell type in peripheral chemoreceptors (Carotid body)?
Glomus Cells - neuronal phenotpye, fires action potentials
What other type of cell can also be found in peripheral chemoreceptors (Carotid Body)?
Type II Cells - Supporting cells
What sends singnals to the respiratory centres in the medulla?
Cranial nerve IX or glossopharnygeal nerve afferents
What are BK K+ Channels?
Calcium activated potassium ion channels, in normal conditions they are open and drive the membrane potential towards negative
When BK K+ channels are inhibited…
Potassium ions cannot enter leading to depolarisation
What’s the function of central chemoreceptors?
To drive our normal breathing
What is the main activator of the central chemoreceptors?
Hypercapnia - the increase in PCO2
Where are central chemoreceptors located?
In the brain parenchyma, bathed in BECF (Brain extracellular fluid)
in the ventrolateral medulla
Separated from the artierial blood supply by the BBB (Blood brain barrier)
Why do some infants end up with SIDS?
Defect in the central chemoreceptor pathways resulting in respiratory problems.
