Lecture 7

Question 1

The extent of gas dissolving into a fluid depends on …

Answer 1

• 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)

Question 2

In Ficks Law of Diffusion can Area be changed and what is it based on

Answer 2

Area can not be changed

it is based on your body size, not changed with fitness

Question 3

In Ficks Law of Diffusion can Thickness be changed and what environment can worsen it

Answer 3

Thickness of membrane can not be changed

high altitude or certain conditions can worsen it (make it thicker)

Question 4

In Ficks Law of Diffusion can Pressure Gradient be changed and what does this mean

Answer 4

Pressure gradient CAN be changed

either more pressure in the alveoli or less pressure in the blood will increase the diffusion rate

Question 5

what happens immediately to inspired air that you have just breathed in

Answer 5

it gets humidified which decreases the pressure

Question 6

why is PAO2 in the alveoli (~100 mm Hg) lower than in atmosphere (~159)

Answer 6

because ….
- Water has evaporated into it (in airways, well before alveoli)

• CO2 diffuses into it (from blood)

Question 7

why is oxygen a limiting factor of gas exchange

Answer 7

because it requires high pressure gradients

Question 8

why can CO2 be exchanged at an equivalent rate of O2 but will a smaller pressure gradient

Answer 8

because CO2 is very soluble

Question 9

what does your ability to keep the pressure gradient high in the alveoli determine

Answer 9

how fast you can diffuse oxygen into the blood

Question 10

why is CO2 high in muscle

Answer 10

due to metabolism, increases with exercise

Question 11

why is there a large drive for O2 to go into muscle

Answer 11

there is a large pressure gradient

Question 12

what are the 4 inter-dependent pulmonary factors that can limit exercise

Answer 12

• desaturation of O2
• high airway resistance
• pulmonary pressure effects on cardiac output
• high work of breathing

Question 13

how does pulmonary pressure impact cardiac output

Answer 13

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

Question 14

why do females have lower levels of haemoglobin in their blood

Answer 14

they have lower amounts of testosterone, that is what determines haemoglobin levels

Question 15

is oxygen soluble in blood

Answer 15

oxygen is poorly soluble in blood

Question 16

what % of oxygen in blood is bound to haemoglobin and what is in plasma

Answer 16

99% is bound to haemoglobin

around 3ml O2.L-1 plasma (establishes PO2)

Question 17

compare offloading of oxygen from haemoglobin at rest and during exercise

Answer 17

~25% offloaded to tissues at rest

~80-90% offloaded to tissues during exercise

Question 18

% of how CO2 is found in the blood

Answer 18

5-10% dissolved in plasma (establishes PCO2)

~20% bound to haemoglobin

60-80% as bicarbonate

Question 19

how does the curve shift due to the Bohr effect

Answer 19

curve shift down to right (in favour of offload)

Question 20

what conditions cause the Bohr effect to occur

Answer 20

• increased temperature
• decreased pH
• increased CO2

Question 21

what happens during exercise in terms of the Bohr effect

Answer 21

as exercise gets harder the muscle has to work more, these conditions increase more in the muscle as metabolism is increased

Question 22

Where is 2,3 DPG produced

Answer 22

in red blood cells as a by product of glycolysis

Question 23

where is production of 2,3 DPG higher and what is it similar to

Answer 23

acts similarly to the Bohr effect

• higher in altitude, females, exercise

Question 24

why do females typically have higher amounts of 2,3 DPG

Answer 24

means they can offload more oxygen into the tissue which compensates for the fact that they have lower haemoglobin concentration

Question 25

what are three buffering mechanisms in the body

Answer 25

• chemical (bicarbonate, phosphate, protein (incl Hb))
• pulmonary ventilation
• renal function

Question 26

if the lungs aren’t maximally utilised in exercise, are they a limiting factor during intense exercise

Answer 26

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