Lecture 7 Flashcards
The extent of gas dissolving into a fluid depends on …
- Pressure of the gas
- Solubility of the gas (CO2 is 24 x more soluble than O2)
- Temperature of the gas
- Time available (if time constraint)
In Ficks Law of Diffusion can Area be changed and what is it based on
Area can not be changed
it is based on your body size, not changed with fitness
In Ficks Law of Diffusion can Thickness be changed and what environment can worsen it
Thickness of membrane can not be changed
high altitude or certain conditions can worsen it (make it thicker)
In Ficks Law of Diffusion can Pressure Gradient be changed and what does this mean
Pressure gradient CAN be changed
either more pressure in the alveoli or less pressure in the blood will increase the diffusion rate
what happens immediately to inspired air that you have just breathed in
it gets humidified which decreases the pressure
why is PAO2 in the alveoli (~100 mm Hg) lower than in atmosphere (~159)
because ….
- Water has evaporated into it (in airways, well before alveoli)
- CO2 diffuses into it (from blood)
why is oxygen a limiting factor of gas exchange
because it requires high pressure gradients
why can CO2 be exchanged at an equivalent rate of O2 but will a smaller pressure gradient
because CO2 is very soluble
what does your ability to keep the pressure gradient high in the alveoli determine
how fast you can diffuse oxygen into the blood
why is CO2 high in muscle
due to metabolism, increases with exercise
why is there a large drive for O2 to go into muscle
there is a large pressure gradient
what are the 4 inter-dependent pulmonary factors that can limit exercise
- desaturation of O2
- high airway resistance
- pulmonary pressure effects on cardiac output
- high work of breathing
how does pulmonary pressure impact cardiac output
the more pressure you have to generate pumping air, will limit blood moving in and out of the heart as they are in the same area
why do females have lower levels of haemoglobin in their blood
they have lower amounts of testosterone, that is what determines haemoglobin levels
is oxygen soluble in blood
oxygen is poorly soluble in blood
what % of oxygen in blood is bound to haemoglobin and what is in plasma
99% is bound to haemoglobin
around 3ml O2.L-1 plasma (establishes PO2)
compare offloading of oxygen from haemoglobin at rest and during exercise
~25% offloaded to tissues at rest
~80-90% offloaded to tissues during exercise
% of how CO2 is found in the blood
5-10% dissolved in plasma (establishes PCO2)
~20% bound to haemoglobin
60-80% as bicarbonate
how does the curve shift due to the Bohr effect
curve shift down to right (in favour of offload)
what conditions cause the Bohr effect to occur
- increased temperature
- decreased pH
- increased CO2
what happens during exercise in terms of the Bohr effect
as exercise gets harder the muscle has to work more, these conditions increase more in the muscle as metabolism is increased
Where is 2,3 DPG produced
in red blood cells as a by product of glycolysis
where is production of 2,3 DPG higher and what is it similar to
acts similarly to the Bohr effect
- higher in altitude, females, exercise
why do females typically have higher amounts of 2,3 DPG
means they can offload more oxygen into the tissue which compensates for the fact that they have lower haemoglobin concentration
what are three buffering mechanisms in the body
- chemical (bicarbonate, phosphate, protein (incl Hb))
- pulmonary ventilation
- renal function
if the lungs aren’t maximally utilised in exercise, are they a limiting factor during intense exercise
it is complicated, but they can = for example in needing a lot of energy and thus blood supply
you can not keep driving them at high ventilation without it costing something
