Control of Breathing Flashcards
What is the atmospheric concentration of CO2?
0.033%
Is alveolar air identical to atmospheric air?
No it differs due to moisture and mixing with old air
How does water impact alveolar air?
Air si humidified and the water vapour dilutes inhaled gases
How does old air impact alveolar air?
Inspired air mixes with old air in dead space further diluting it
What is the pO2 in the alveoli?
100 mmHg
Why does gas exchange occur in the lungs?
Blood arriving at the lungs has lower pO2 than the alveoli
What four factors affect diffusion rate?
- Partial pressure
- Surface area
- Membrane thickness
- Gas diffusion constant
How is the most oxygen transported in the blood?
Bound to haemoglobin
What small faction of oxygen is not transported by haemoglobin?
A small percentage is dissolved in plasma
What determines the amount of dissolved oxygen?
The partial pressure of oxygen
Does O2 bound to Hb contribute to pO2?
No pO2 only reflects dissolved O2 in plasma
What is full haemoglobin saturation?
When all four O2 binding sites on Hb are occupied
What determines haemoglobin saturation most strongly?
The pO2 of the blood
How does haemoglobin saturation responds to pO2 between 100-60 mmHg?
It remains relatively constant acting as a large O2 reservoir
How does CO affect O2 transport?
CO competes with O2 for haemoglobin binding and has stronger affinity
What are the three methods of CO2 transport in blood?
- Dissolved in plasma
- Bound to haemoglobin
- Bicarbonate ions
How does CO2 bind to haemoglobin?
It binds to the globin part not the heme group
How much CO2 is transported bound to haemoglobin?
About 25%
How much CO2 is transported as bicarbonate?
70%
What is hypoxia?
Low arterial pO2
What is hyperoxia?
High arterial pO2
What is oxygen toxicity?
Cellular damage caused by excessive O2
What is hypercapnia and what causes it?
High arterial pCO2 caused by hypoventilation
What is hypocapnia and what causes it?
Low arterial pCO2 caused by hyperventilation
