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31 Cards in this Set

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  • Back
what is ventilation?
bringing air into certain areas
what is perfusion?
amount of blood into area
what is ventilation-perfusion coupling?
diversion of pulmonary blood poorly ventilated areas to well ventilated areas
when does efficient gas exchange occur?
when perfusion is balanced with ventilation
when is perfusion balanced with ventilation?
amount of blood flowing in alveolar capilaries balances with amount of gas reaching the alveolus
what two things can be controlled in order to accomplish efficient gas exchange?
1. if high PCO2 in alveolus
2. if low PO2 in alveolus
what happens when PCO2 is high in alveolus?
air flow causes the relaxation of local bronchiole which increases gas flow
what happens when PO2 is low in alveolus?
blood flow constriction of local arterioles decreases blood flow to affected alveolies
-shunts blood to better ventilated areas
what is oxygen transport?
formation of Hb is an easily reversible reaction: Hb + O2=Hb - O2
what is the relationship between PO2 and O2?
the higher the PO2 the more O2 combines with Hb
where is PO2 the highest?
pulmonary capillaries
where is PO2 lowest?
tissue capillaries; O2 diffuses into tissue cells
what four factors affect HB's affinity for oxygen?
1. acidity (pH)
2. PCO2
3. Temperature
4. BPG
how does acidity affect affinity of HB for O2?
-decreasing pH decreases affinity
-increasing acidity enhances unloading: H+ bind to aa's in Hb altering its structure- low O2 carrying capacity
what is the Bohr effect?
a shift in dissociation curve to the right due to a decrease in pH causing Hb to bind to O2 with less affinity; less O2 in blood in that tissue
how does PCO2 affect Hb's affinity?
also enhances acidity; shift dissociation curve to the right
what are the three forms of CO2 in blood?
1. 7% directly dissolved in blood as CO2- can be directly exhaled
2. 23% binds to Hb altering its shape- carbaminohemoglobin
3. 70% converted to carbonic acid
what is carbonic annhyorase?
CH; always in RBC
how do bicarbonate ions act as blood buffers?
theyre toxic to RBCs
what do H+ and Cl- ions do?
H+ binds to Hb and Cl- diffuse in to balance charges
how does temperature affect Hb's affinity?
changes intemp alters shape of hemoglobin molecule
what happens to O2 release when you increase temperature?
it increases O2 release; metabolically active cells
what are metabolically active cells?
require more O2, release more acids and heat
-promoted
what happens as body temperature lowers and metabolism slows down?
-O2 requirements?
-affinity?
-dissociation curve switches to the left
what is BPG?
3-biphosphoglycerate; a byproduct of glycolysis
how does BPG affect Hb's affinity?
-it binds to the Hb molecule altering its structure
-it decreases affiniry of Hb for O2 and oxygen is released
what two factors case in increase in BPG?
1. higher altitudes
2. hormones- increase metabolic activity
what 5 hormones are involved when theres an increase in BPG?
thyroxine, human Gh, E, NE, testosterone
what three forms is CO2 carries in blood?
1. freely dissolved in plasma (7%)
2. bound to Hb (23%)
3. chemically reacted to form bicarbonate (70%)- complete reverse reaction
how is CO2 chemically reacted to form bicarbonate?
-H+ neutralized by Hb
-bicarbonate is hazardous in RBC
why is bicarbonate hazardous in RBCs?
necause its exchaged for Cl- and acts as a buffer in plasma