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PHGY 216 Exam With Complete Solution
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PHGY 216 Exam With CompleteSolution
daltons law for partial pressures - Answer - pressure exerted by gas in a mixture is
proportional to the percentage of gas in the mixture.
For example, 79% of air is nitrogen so the partial pressure of nitrogen is 0.79 x 760
mmHg, which is 600 mmHg.
Oxygen is 21% of air, so its partial pressure is 160 mmHg.
The amount of carbon dioxide in air is so little that its partial pressure is only 0.23 mmHg
two key factors that determine the amount of gas that can dissolve in a liquid - Answer 1.
Partial pressure in air:
the greater its partial pressure, the more gas will be driven into the liquid
2. Solubility in the liquid:
the more soluble a gas is in a liquid, the more will dissolve
Partial Pressure:
The pressure that would be exerted by one of the gases in a mixture of gases, if it
occupied the same volume on its own
how does capillary transit time impact gas exchange - Answer Gases can only be
exchanged between the blood and the alveoli when the blood is in the pulmonary
capillaries.
Because of this, the flow rate of the blood can influence gas exchange.
At rest, blood remains in the pulmonary capillaries for about 0.75 seconds-three times
as long as necessary for exchange.
-during exercise, capillary transit time* only decreases to 0.4 seconds.
As you can see, under physiological conditions, capillary transit time is not a limitation
to gas exchange.
If diffusion is impaired, equilibration still occurs before the blood reaches the end of the
capillary, but only at rest.
If the time available for diffusion decreases due to (i.e.) an increase in cardiac output,
the person with normal diffusion is unaffected, but the impaired person will experience a
drop in arterial PO2.
, hemoglobin structure - Answer -four protein subunits
-Each subunit consists of a protein chain and a heme group, which contain the iron
molecules to which oxygen binds.
Haemoglobin (Hb):
Hb is an iron-bearing protein within red blood cells that can carry oxygen.
- 98.5% of circulating oxygen is bound to Hb.
Steep portion of Oxyhemoglobin Dissociation Curve
vs
Plateau portion - Answer steep: 0 and 60 mmHg c
-corresponds to the range of PO2 that is found in the systemic capillaries
- tissues can withdraw large amounts of oxygen for only a small drop in capillary Po2
Plateau:
- represents the PO2 range found in the pulmonary capillaries where the Hb is collecting
O2.
-plateau phase of the curve represents a margin of safety.
4 factors affecting the dissociation curve - Answer -pH, enhances dissociation of O2
from Hb
-BPG, shift right
-CO2,
shifts to the right (decreased % saturation for a given PO2)
-CO,
shifts left
how does carbon dioxide travel within the circulatory system - Answer Physically
dissolved
-CO2 is 20 times more soluble in solution than O2, more CO2 is dissolved in the plasma.
- 5-10% of total blood CO2 is freely dissolved, this fraction accounts for the 46 mmHg
partial pressure of CO2 when blood leaves the systemic capillaries.
Bound to haemoglobin
CO2 doesnt bind to the haem-O2 binding sites, binds to the globin part of the molecule.
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