Fred 2015 questions

[student456]

Why would the Arterial Baroreceptor firing rate be decreased?

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[StilgarMD]

Shot in the Leg - Lots of Blood loss = Hypovolumia = Sympathetic responses to preserve pressure.

Arterial Baroreceptor Firing Rate = Lower, because these receptors are often called "Stretch" receptors and whether they are in the Aorta or Carotid, they will be less stretched, signalling to the brain that a sympathetic response is needed to preserve perfusion.

Systemic Vascular Resistance = Takes into account both Veins and Arteries. Arteries are vasoconstricted, so this is higher.

Pulmonary Vascular Resistance = Not sure why this would go up. The only time I ever hear about PVR is when there is hypoxia and the vessels constrict, but perhaps the same principles are at work in the lung and systemic vasculature when it comes to shock.

System Capillary Fluid Transfer = This patient has a BP of 80/60, which means at the Capillary interface, there is less hydrostatic pressure and that means the forces will favor absorption.

If anyone wants to chime in on PVR, I'd appreciate the insight.

 

[worldbeater]

Arterial Baroreceptor Firing Rate = Lower, because these receptors are often called "Stretch" receptors and whether they are in the Aorta or Carotid, they will be less stretched, signalling to the brain that a sympathetic response is needed to preserve perfusion.

Nice point. Another way to say the whole sequence is patient is losing blood so they are in a low volume state -> decreased venous return -> decreased end diastolic volume -> decreased cardiac output -> decreased flow(amount of blood) to carotid sinus, less blood touching the sides of the carotid [what is nicely quoted above]-> decrease in firing of CN IX -> decreased in firing of CN X -> Increase in heart rate

The 1st 7 values will all go in the same direction, CN X is inhibitory, the heart rate will go in the opposite direction (if you decrease an inhibitory action, you will increase the heart rate)

Pulmonary Vascular Resistance = Not sure why this would go up. The only time I ever hear about PVR is when there is hypoxia and the vessels constrict, but perhaps the same principles are at work in the lung and systemic vasculature when it comes to shock.

Yeah I think your right, you have lost blood, so the amount total amount of oxygen in your blood (Pa02 + Sa02) has gone down, which will cause a hypoxic response -> causing the lungs only to vasoconstrict due to lack of 02 would be my guess

I've never heard of System Capillary Fluid Transfer before.

 

[student456]

Thank you guys...