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