Respiratory Physiology Part C: Oxygen Transport

Question 1

What is partial pressure of gases?

Answer 1

• the pressure exerted by a single gas in a mixture of gases
• pressure gradients promote gas movements
• H to L

Question 2

What is the partial pressure number?

Answer 2

160mmHg

Question 3

What are the 2 ways oxygen is carried?

Answer 3

1. Dissolved in Plasma (1.5%)

2. Bound to Hemoglobin (98.5%)

Question 4

what happens to Oxygen dissolved in plasma at lung capillaries

Answer 4

goes from H to L pressure (150-40mmHg)

Question 5

What happens to oxygen dissolved in plasma at tissue capillaries?

Answer 5

• Arterial P = 95mmHg
• Resting Venous + ISF P = 40 mmHg
• ICF P = < 40 mmHg
• O2 diffuses: capillary -> ISF -> cell (down P gradient)

Question 6

What happens to oxygen bound to hemoglobin?

-how many O2 can bind to each hemoglobin?

Answer 6

-4

Question 7

O2-Hb dissociation curve shows the relationship between:

Answer 7

P and % Hb

-shows how much O2 is on Hb for a given amount of dissolved O2

Question 8

Plateau of O2-Hb curve

60-100 mmHg

Answer 8

= range of PO2 in lung at which Hb picks up O2 (Hb 97% saturated)

• if alveolar PO2 ⇓ a little below normal ⇒ little change in Hb saturation
  e. g. at high altitude ⇒ if alveolar PO2 above 60 mm Hg ⇒ Hb carries normal amount of O2

Question 9

Steep Portion of O2-Hb curve

Answer 9

• range of PO2 in tissues - O2 unloaded from Hb
• at rest: ISF PO2 = 40 mm Hg ⇒ Hb = 75% saturated (97% - 75% = 22% unloaded to cells)
  - allows holding of breath
• high metabolism (e.g. exercise): ISF PO2 = 20 mm Hg ⇒ Hb = 40% saturated (97% - 40% = 57% or more O2 is unloaded easily)

Question 10

Shift to Right in O2-Hb curve

Answer 10

• for a given PO2, get less Hb saturation i.e. O2 unloads more easily/loads less easily
• occurs when:
  i. ⇑ PCO2
  ii. ⇓ pH (related to ⇑ CO2, also lactic acid) = decreased ability of O2 to bind to Hb when H+ is bound to globin (= Bohr effect)
  iii. ⇑ temp
• All occur when ⇑ cell metabolism e.g. exercise – Hb releases more O2

Question 11

Shift t o Left in O2-Hb curve

Answer 11

-For a given PO2, get more Hb saturation ie O2 loads more easily, unloads less easily
-occurs when:
i. ⇓ PCO2
ii. higher pH
iii. ⇓ temp
= conditions at lung (⇓ temp due to evaporative cooling)