Respiratory System, Lecture 5 Flashcards
Gas Transport - Henry’s Law
- at constant temperature, amount of gas dissolved in a liquid is directly proportional to partial pressure of gas above liquid (outside of liquid)
- liquid is blood and gases are oxygen and carbon dioxide
- problem – cannot dissolve enough oxygen and carbon dioxide into blood to meet tissue metabolic needs (cannot dissolve enough to carry to tissue, provides a limitation)
- solution – gas transporters to bind gases and help move enough to meet tissue metabolic needs (cannot get enough dissolve so bind to transporters to get it to where it needs to be)
◦ solves the transport problem but creates the problem of the gas not being dissolved as it is binded - problem – only dissolved gas can participate in gas exchange (if it is bound to a transporter it becomes too large of a molecule - cannot do anything related to gas exchange)
- solution – need to be able to bind to a transporter for gas transport; let go and return to dissolved state for gas exchange (temporary state)
◦ binds to transporter to get somewhere and then let go to let it do its exchange
Manipulate affinity (tightness of binding)
- lower affinity: more likely to let go of transporter (unloading)
- higher affinity: more likely to hold on to transporter (loading - loading gas onto transporter) (do not want to let go until we get to place of exchange)
- we can manipulate affinity when we need particular things (none are bad)
Gas Transport - Oxygen
- 1.5% of oxygen dissolved in plasma (only little available for exchange, meaning most of it is going to move around being to the hemoglobin - transporter)
- 98.5% oxygen binds hemoglobin (Hb) for transport as oxyhemoglobin (HbO2) inside erythrocyte
- each Hb can bind 0-4 oxygen molecules
◦ at 100% = all sites have an oxygen; fully saturated
◦ lower percentage = not all sites have an oxygen; partially saturated - when we move from alveoli to capillaries most of it is going to bind to hemoglobins
Gas Transport - Oxygen (external and internal respiration)
external respiration:
- oxygen mainly goes into red blood cell (erythrocyte)
- moved into blood from alveoli, dissolved oxygen being picked up by hemoglobin inside blood cell and is going to take it to site of internal respiration
- towards binding
internal respiration
- letting go of transporter back into dissolved state
- bringing it back out of red blood cell into tissue cells in dissolved state
- reversal of external process, just going to tissue now instead
Oxygen-Hemoglobin Dissociation Curve
- increasing partial pressure oxygen:
◦ more oxygen binds to Hb (increasing Hb-O2 saturation (Hb Sat); loading) - higher po2 gives higher saturation - decreasing partial pressure oxygen:
◦ less oxygen binds Hb (decreasing Hb-O2 saturation; unloading)
remember: - sometimes we want high Hb saturation (loading for gas transport)
- sometimes we want low Hb saturation (unloading for gas exchange
Oxygen-Hemoglobin Dissociation Curve - resting levels:
- leave lungs – returning to heart – pump out into systemic arteries – 100 mmHg – ~100% saturation
- leaving tissues in systemic veins – returning to heart – to lungs – 40 mmHg – 78% saturation
Oxygen-Hemoglobin Dissociation Curve (plateau portion and steep portion)
- in plateau phase the PO2 change does not lead to much change in saturation
- in steep portion much more significant change
- the initial things changing po2 would not be very noticeable
- not a linear relationship; “S” shaped
plateau portion (PP):
- decrease in oxygen; little effect on saturation (PO2 100 mmHg to 80 mmHg; Hb Sat 100% to 98%)
- provides a safety margin for decreasing oxygen
steep portion (SP):
- decrease in oxygen; large decrease in saturation (PO2 40 mmHg to 20 mmHg; Hb Sat 78% to 30%)
Oxygen-Hemoglobin Dissociation Curve - Exercise
- leave lungs – returning to heart – pump out into systemic arteries – 100 mmHg – ~100% saturation (still on plateau portion)
- leaving tissues in systemic veins - returning to heart – to lungs – 20 mmHg – 30% saturation (well down steep portion)
- more oxygen unloaded from Hb and made available as dissolved; greater internal respiration as oxygen taken by active muscles (greater a-v O2 diff)
- PO2 most important for Hb Sat but also effected by acidity, CO2, and temperature (curve shifts)
- right shift (purple): decreased affinity – increased unloading / lower Hb Sat / more oxygen for gas exchange (when they intersect - you can see lower saturation)
- left shift (green): increased affinity – decreased unloading / greater Hb Sat / less oxygen for gas exchange Bohr effect
- in active muscles, CO2 and H+ levels are high (from metabolism / lactate production)
- oxygenated blood flowing past affected by these conditions and affinity of Hb for oxygen decreases (right shift)
- allowing oxygen to unload and internal respiration of oxygen to active muscles
- Hb, having let go of oxygen, available to bind CO2 and H+ for gas transport to removal areas (lungs – external respiration / kidneys – urinary output)
- if you increase concentration (up) is increase acidity (up) which is decreasing pH (down)
Gas Transport - Carbon Dioxide
- 7% carbon dioxide dissolved in plasma and in erythrocyte (red blood cell)
- can dissolve more CO2 in blood than oxygen
- 23% carbon dioxide binds Hb for transport as carbaminohemoglobin (HbCO2) inside erythrocyte
- 70% carbon dioxide converted to bicarbonate inside erythrocyte and then moves out of erythrocyte and is dissolved in plasma
