Respiration and Breathing 3 Flashcards
What does gravity influence
Ventilation and perfusion
Why is local matching of ventilation and perfusion important
To optimise gas exchange in lungs
Why is there better airflow at the base of the lungs
Due to pressure gradients
What is perfusion
Blood supply
What happens when there is no ventilation and good perfusion
Blood passing through the lung without coming into contact with alveolar air (right to left shunt)
What happens when there is good ventilation but no perfusion
Anatomically an increase in dead space or ventilated alveoli are not perfused
What mechanisms are in place to prevent alveolar ventilation rate matching perfusion rate
Achieved by modulation of blood flow.
What happens during hypoxia
When there is low PO2 vasoconstriction occurs. Blood is directed away from poorly ventilated areas. The response is very non-linear.
What happens during ventilation
The delivery of oxygen and removal of carbon dioxide.
Describe what happens to blood before perfusion
Blood from ventricle. Has high levels of CO2 and low levels of O2
How are alveoli adapted for gas exchange
Fluid lining of pulmonary surfactant which reduces pressure. Surrounded by a single cell capillary. Have a very small interstitial space (0.5 um)
What is transfer of oxygen influenced by
Diffusion across red blood cell membrane. Combination with haemoglobin.
What does combination of oxygen with haemoglobin do
Increases affinity and increases O2 capacity of blood.
Why is haemoglobin vital
Removes O2 so maintains conc gradient
What is the equation for oxygen and haemobglobin
O2 + Hb -> HbO2
Describe the Haemoglobin-O2 dissociation curve
% haemoglobin saturation (0-100)
PO2 of blood (mm Hg)
ml O2 per 100ml in blood (0-20)
Describe haemoglobin binding with oxygen
4 binding sites. Co-operation between sites so more sites bound easier it is to bind to another O2. Affinity depends on amount of O2 already bound
Describe the Bohr Shift
In the presence of CO2 there is a change in the haemoglobin bidning of O2. An increase in PCO2 helps haemoglobin to release O2 where metabolsim is taking place
Which factors result in the Bohr shift and so the release of O2 from haemoglobin
Increase PCO2 (metabolsim). Increase in conc H+ (metabolsim). Increase in temperature (muscles contract). Increase in BPG (hypoxia).
What is the PO2 in body tissue
Less than or equal to 40 mm Hg
What is the PO2 of oxygen in the alveoli
100 mm Hg
What is the PCO2 in the body
Greater than or equal to 46
What is the PCO2 in the alveolus
40 mm Hg
How is carbon dioxide carried in the blood
Chemical comination in plasma
CO2 + H2O -> H2CO3 -> H+ + HCO3(-)
How much CO2 is carried in the plamsa
70%
How much CO2 is bound to Hb
30%
What is the name of the compound formed when CO2 bonds to Hb
carbamino compounds
