Just have a question regarding sympathetic stimulation of heart regarding cardiac output. Cardiac output is basically controlled by everything that affects blood flow and ultimately venous return.
Venous return can be calculated as:
VR = (Psf-PRA)/RVR where Psf: mean systemic filling pressure; PRA: right atrial pressure; RVR: resistance to venous return.
Sympathetic stimulation makes the heart pump stronger. The other part it affects is the systemic circulation where it increases the mean systemic filling pressure because of vasoconstriction of peripheral vessels (especially the veins), and this increases the resistance to venous return. So basically, one factor that increases VR (Psf increase) and one that decreases (RVR increases).
What factors makes the venous return, and thereby CO, increase so much when maximally sympathetic stimulated?
Will the resistance to venous return be overdriven by the mean systemic filling pressure? And the heart's stronger beat keep the pressure difference?
Is this increase in resistance to venous return just a necessary "brake"?
Additionally, the pressure in right atria will increase and also decrease the VR looking at the forumula. Even though I get that if Psf would be like 14mmHg and right atrial pressure 12 mmHg it would be a pressure difference that would keep the blood flowing into the heart, no matter the volume.
Venous return can be calculated as:
VR = (Psf-PRA)/RVR where Psf: mean systemic filling pressure; PRA: right atrial pressure; RVR: resistance to venous return.
Sympathetic stimulation makes the heart pump stronger. The other part it affects is the systemic circulation where it increases the mean systemic filling pressure because of vasoconstriction of peripheral vessels (especially the veins), and this increases the resistance to venous return. So basically, one factor that increases VR (Psf increase) and one that decreases (RVR increases).
What factors makes the venous return, and thereby CO, increase so much when maximally sympathetic stimulated?
Will the resistance to venous return be overdriven by the mean systemic filling pressure? And the heart's stronger beat keep the pressure difference?
Is this increase in resistance to venous return just a necessary "brake"?
Additionally, the pressure in right atria will increase and also decrease the VR looking at the forumula. Even though I get that if Psf would be like 14mmHg and right atrial pressure 12 mmHg it would be a pressure difference that would keep the blood flowing into the heart, no matter the volume.