PHGY 210 Lecture Notes - Lecture 37: Globin, Vascular Resistance, Conformational Change

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21 Jul 2016
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xenon.%The%general%trend%is%that%there%is%more%blood%flow%at%the%bottom%of%the%lungs%than%at%the%top%
(bc%of%gravity).%There%would%be%less%difference%if%the%patient%was%lying%down.%%
!We%can%divide%the%lungs%into%3%zonesN%the%blood%flow%as%a%ftn%of%height%form%the%bottom%to%top%of%the%
lungs.%The%arteries%and%capillaries%and%the%veins%are%affected%by%the%pressure%of%the%alveoli%
surrounding%themN%they%can%squash%the%caps,%but%not%at%the%bottom%of%the%lungs%where%there%is%high%
pressureN%high%arterial%pressure%which%is%still%higher%than%the%venous%and%alveolar%acting%as%a%
gradient.%But%higher%in%the%lungs,%the%alveolar%pressure%is%higher%than%the%arterial,%squeezing%the%
caps%and%leading%to%a%reduction%in%blood%flowN%note%that%the%venous%is%still%lower%than%arterial%
inducing%a%gradient%a%flow.%This%is%pathological!%It%doesn’t%occur%in%normal%subjects,%maybe%after%a%
hemorrhage.%Blood%flow%is%affected%by%gravity%and%there%is%more%flow%at%the%bottom%than%at%the%top.%
There%are%alveolar%vessels%(the%vessels%in%between%the%alveoli),%but%there%are%other%vessels%that%are%
subjected%by%the%pressures%of%the%pleural%space!!!!%Lung%volume%affects%pulmonary%vascular%
resistance.%Above%FRC,%the%alveolar%vessels%are%stretched%longitudinally%and%this%increases%the%
diameter%leading%to%an%increase%in%resistance%(%this%slide%won’t%be%asked%on%the%exam).%%
!Effects%of%gravity%on%ventilationN%do%we%have%uniform%ventilation?%Or%is%it%better%at%the%bottom%with%
increase%flow?%The%alveoli%are%more%open%at%the%top%of%the%lungs%because%the%weight%at%the%bottom%
pulls%the%alveoli%at%the%top%open.%So%the%preferential%ventilation%is%at%the%bottom%because%the%top%
ones%were%already%open%and%there%was%already%air%in%it%and%gas%exchange,%and%so%the%fresh%and%
preferential%ventilation%is%at%the%bottom%(the%new%air)!!%Inhaling%radioactive%xenonN%you%would%see%
more%ventilation%in%the%lower%lung%could%test%this.%Look%at%the%slide%to%note%the%differences.%Because%
there%is%a%cross%over,%at%the%top%you%get%more%ventilation%than%perfusion,%and%this%is%the%opposite%at%
the%bottom.%There%is%a%greater%difference%between%the%bottom%and%top%of%the%lung%with%blood%flow%
rather%than%ventilation.%In%space,%the%relationship%is%much%flatter.%Ventilation%will%still%be%curved,%but%
flatter.%%
!How%do%we%measure%pulmonary%blood%flow?%The%o2%consumption%per%minute%is%=%to%the%o2%taken%by%
the%blood%in%one%min.%what%is%the%o2%picked%up%by%the%blood?%There%is%a%pressure%gradient%of%
60mmHG,%if%the%cells%is%more%o2,%the%p02%will%increase%and%there%will%be%a%greater%gradient%and%more%
will%diffuse.%The%o2%picked%up%by%the%cells%is%=%to%the%o2%picked%dup%by%the%lungs%in%one%min.%refer%to%
slide%for%the%equations,%but%they%won’t%be%on%the%exam.%So%figure%out%the%o2%consumption%and%
measure%it%to%figure%out%the%pulmonary%blood%flow.%If%you%are%decreasing%the%metabolism,%the%
gradient%will%be%lower%as%well%as%diffusion%%
!Transport%of%02N%the%amt%of%o2%dissolved%is%proportion%to%partial%pressure%of%that%gas,%but%the%
solubility%of%o2%in%fluid%is%lowN%they%counteract%each%other.%In%100ml%of%plasma,%only%.3ml%of%O2%can%
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