PHGY 210 Lecture Notes - Lecture 42: Trachea, Angiotensin, Skeletal Muscle

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21 Jul 2016
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versa.%This%also%increases%the%contractility%of%the%vessels%and%increase%venoconstriction.if%you%
increase%the%heart%rate,%the%cardiac%output%goes%up,%follow%slide%
!We’re%not%responsible%for%the%slides%that%he%skips!%
!If%you%have%a%fall%in%the%arterial%blood%pressure,%we’ll%lose%na%and%water%in%the%urine.%So%if%there%is%a%
rise%in%the%blood%pressure,%the%kidney%will%extract%more%water%(pressure%diuresisN%because%a%change%
in%pressure%sparks).%Diuretics%increase%the%rate%of%urinating%so%that%the%bv%falls.%%
!Effects%of%angiotensinN%if%the%blood%pressure%fall,%the%pressure%of%the%renal%artery%falls.%This%is%sensed%
and%renin%is%secreted%into%circulation,%it%acts%on%angiotensinogen%(made%in%the%liver)%and%this%cleaves%
off%10%aa%and%this%new%cleaved%structure%becomes%angiotensin%1%%
o!Angiotensin%2%binds%to%a%receptor%and%makes%the%arterials%constrict.%So%negative%feedback%
loop%
o!It%can%also%have%an%effect%on%the%brainN%stimulate%ADH%or%vasopressin%(pressure%increasing%
agent)%and%is%a%vasoconstrictor.%This%is%against%diuresis%ie%keep%more%volume%in%the%blood%
o!If%the%bp%falls,%ACE%converts%the%angiotensin%1%to%2.%It%then%binds%to%a%angiotensin%2%receptor%
on%the%andrenal%glandsN%then%secretion%of%aldosteroneN%increase%blood%volumeN%then%neg%
feedback.%%
!Antihypertensive%agentsN%ace%inhibitors%(no%angiotensin%2%then)%
o!At%2%receptor%blocks%
o!Aldosterone%antogonistsN%receptors%for%aldosterone%are%blked%by%something%else%
o!Renin%inhibitN%lets%at%1%is%made%therefore%less%2%
!OrthostasisN%standing%uprightN%when%you%stand%up,%there%isn’t%any%change%in%the%mean%arterial%blood%
pressure.%The%right%atrial%decreases%because%there’s%a%hydrostatic%pressure%that%pushing%the%weight%
downwards,%so%the%person%loses%about%300mls%of%blood%from%their%central%blood%volume%(blood%in%
chest).%The%blood%is%pooled%at%the%bottom,%but%its%obviously%replaced.%But%the%right%atrium%still%has%
less%because%there%is%a%pool.%When%we%stand%up,%our%heart%rate%increases.%So%even%though%the%stroke%
volume%decreases,%the%cardiac%output%is%still%high%because%of%our%increased%heart%rate.%The%
baroceptor%will%also%increase%the%contractility%of%the%heartN%so%the%sympa%was%also%activated.%If%this%
didn’t%happen,%it%would%have%fallen%to%less%than%.5%(refer%to%slideN%1.5*%.5%=.75).%there%is%then%an%
increase%of%vasostriction%so%we%don’t%faint%if%we%stand%up%(ie%3%rd%response%of%vasocontruction).%
When%we%stand,%we%unconsciously%contract%our%calve%muscles%which%helps%us%constrict%the%blood.%
!Our%muscle%pump%is%the%one%way%valves%and%the%skeletal%muscle!%%
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