Respiratory Physiology Lecture 6 part 27: Oxygen Movement in Lungs and Tissues

Question 1

What drives oxygen movement in lungs and tissue?

Answer 1

Driven by the pressure gradients of two different environments throughout the system so that O₂ can diffuse between locations

Question 2

What are the pressure gradients for P_O2 at the level of the respiratory membrane?

Answer 2

• High P_O2 in the alveoli generates pressure gradient of O₂ to diffuse from alveoli to the blood vessel
• Another pressure gradient is developed between the plasma and RBC to draw in O₂ molecules from the plasma into the RBC

Question 3

P_O2 at the level of the respiratory membrane

Answer 3

• before diffusion to the blood vessel P_O2alv is much greater than P_O2blood
• At equilibrium the P_O2alv = P_O2blood

Question 4

HOw much O₂ is dissolved in plasma vs. attached to Hb?

Answer 4

• dissolved O2₂ = 2%
• O₂Hb = 98%

Question 5

Of oxygen, what contributes to the P_O2 value?

Answer 5

the blood dissolved (2%) but not O₂-Hb

Question 6

What are the pressure gradients for P_O2 at the level of the peripheral tissue?

Answer 6

• Peripheral cells will consume oxygen for cell metabolism (mitochondria); this creates a pressure gradient with mitochondria and intracellular space so that O₂ moves into mitochondria.
• This then creates a pressure gradient between the interstitial fluid and the intracellular fluid promoting the diffusion of oxygen from the interstitial fluid to the intracellular space.
• This then creates another pressure gradient between the plasma and the interstitial fluid causing oxygen to move from plasma to interstitial fluid
• This creates another pressure gradient to move oxygen out of RBC to plasma by unloading it from the Hb turning it into deoxyHb

Question 7

P_O2 at the level of the peripheral tissue

Answer 7

Question 8

What happens when P_O2 is lower in the tissue?

Answer 8

P_O2 of oxygen in the plasma will be reduced with uptake of oxygen to the peripheral tissue which will recall oxygen from inside of blood cells so that equilibrium between oxyHb and deoxyHb moves toward the deoxyHb and more unloading of oxygen occurs

Question 9

What factors effect the O₂ dissocation curve?

Answer 9

• Arterial P_O2
• pH
• temperature
• P_CO2

Question 10

What is the major factor that effect the O₂ dissocation curve the most?

Answer 10

arterial P_O2

Question 11

What happens with shifts to the right for the O₂ dissociation curve?

Answer 11

O₂ affinity of Hb is reduced = more unloading at peripheral tissues

Question 12

What happens with shifts to the left for the O₂ dissociation curve?

Answer 12

O₂ affinity of Hb is increased = less unloading of oxygen to the peripheral tissue

Question 13

How do shifts in thr O₂ dissoction curve affect O₂Hb binding?

Answer 13

Shifts mean that for the same level of P_O2 you will have different percentage of Hb saturation

Question 14

How do changes in pH, temperature and P_CO2 affect the O₂ dissociation curve?

Answer 14

• ⇡ temp. = shift right
• ⇣ temp. = shift left
• ⇡ pH = shift left
• ⇣ pH = shift right
• ⇡ P_CO2 = shift right
• ⇣ P_CO2. = shift left

Question 15

What factors will cause the O₂ dissociation curve to shift right?

Answer 15

• increases in temp., DPG, P_CO2, H⁺
• decrease in pH

Question 16

What is DPG

Answer 16

2,3-diphosphoglycerate

• end product of RBC metabolism

Question 17

Where might an increase in DPG be seen?

Answer 17

An increase in the concentration of this material occurs in chronic hypoxia, for example, at high altitude or in the presence of chronic lung disease