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CVS REGULATION
IN ACTION
Cardiovascular Module – Phase I
Dr. Udara SenarathneDepartment of Biochemistry
Faculty of Medical SciencesUniversity of Sri Jayewardenepura
REVISED BY
Dr. Chandana Hewage(Chairperson of the Cardiovascular Module)
Department of Physiology Faculty of Medical SciencesUniversity of Sri Jayewardenepura
IN THE MORNING… When his mother starts shouting, Siri immediately jumps out of the bed which makes him feel dizzy.
BUT WHY?
a) Reduced sympathetic output
b) Reduced venous return c) Vagal stimulation
CORRECT ANSWER!
Immediate standing from supine position
Decrease venous return to the LA due to venous pooling in the lower limbs
Reduction in EDV causes a fall in stroke volume
CO = HR x SV Thus CO reduces
BP = CO x TPR Thus systolic BP falls
Cerebral perfusion is reduced due to low BP
Feels dizzy
A FACT THAT SIRI ALWAYS KNEW…
That’s why I always turn off the alarm and sleep a little more…
It’s a medical fact. Not because I’m lazy…
AFTER GETTING UP FROM THE BED…
Within a second the dizziness would settle.
BUT WHY?
a) Increased venous returnb) Increased adrenaline
actionc) Decreased baroreceptor
discharge
‘After been
kicked out of
the bed by
his mom’
CORRECT ANSWER!
Fall in the Systolic BP
Baroreceptor discharge rate decrease
Inhibition on vasomotor centre is decreased
Unopposed tonic sympathetic discharge of vasoconstrictor system
Decreased vagal stimulation of heart
BP = CO x TPRThus systolic BP increases
Feels better
He’s been
receiving ‘nice’
comments since then
AFTER COMING TO THE FACULTY…
Anatomy dissection is his least favourite period.WHY IS THAT? Why else? Siri fainted during the very 1st session!
Only after doing the CVS module did he realise the reason…
a) Sympathetic vasodilation in skeletal muscle
b) Vagal stimulationc) Both above
CORRECT ANSWER!
Emotional disturbance
Sympathetic vasodilation in skeletal
muscle causing reduced TPR and venous return
Vagal stimulation causing bradycardia
CO and TPR are reduced.
BP = CO x TPRThus systolic BP
decreases
Faints due to reduced blood flow to brain
+
BOTH MECHANISMS CONTRIBUTE TO VASOVAGAL SYNCOPE
TRY TO WORK OUT LOGICALLY!
“Just a minute! Yesterday she said that X equals 2”
Always ASSESS
yourselfso that you know what
you don’t know!
Click icon to add picture
Practice answering!
Else you might
end up doing this!
Click icon to add picture
Click icon to add picture Practice answering!
Else you might
end up doing this!
Good luck!
