Good day everyone!
I confused on how sympathetic activity can affect blood flow. I checked the forum and I have established some basic understandings but I am unsure if I got it right. I hope to seek some advice.
I understand that increased sympathetic activity = increased vasoconstriction to non-essential organs such as your intestines in the event of fight-or-flight. So with reduced radius = increased resistance = lower blood flow. At the same time, the reduced radius increases pressure so having reduced pressure = having a greater pressure gradient (in relation to high aortic pressure). All that tells us that blood flow will decrease to that non-essential organ.
However, it seems like this is not the case for veins. Vasoconstriction of veins by sympathetic system seems to increase blood flow (or rather venous return) instead of decrease (like above). I understand that since there are one-way valves and so constricting veins will propel blood back into the right side of the heart.
I would like to ask if it is correct for me to say that vasoconstriction of the veins increases pressure, and since the pressure at right side of heart is very low, this establishes a larger pressure gradient and thus a greater flow? But this seems counterintuitive since lowered radius of vessel = higher resistance, then shouldn't blood flow be slower instead of faster?
Thank you!
I confused on how sympathetic activity can affect blood flow. I checked the forum and I have established some basic understandings but I am unsure if I got it right. I hope to seek some advice.
I understand that increased sympathetic activity = increased vasoconstriction to non-essential organs such as your intestines in the event of fight-or-flight. So with reduced radius = increased resistance = lower blood flow. At the same time, the reduced radius increases pressure so having reduced pressure = having a greater pressure gradient (in relation to high aortic pressure). All that tells us that blood flow will decrease to that non-essential organ.
However, it seems like this is not the case for veins. Vasoconstriction of veins by sympathetic system seems to increase blood flow (or rather venous return) instead of decrease (like above). I understand that since there are one-way valves and so constricting veins will propel blood back into the right side of the heart.
I would like to ask if it is correct for me to say that vasoconstriction of the veins increases pressure, and since the pressure at right side of heart is very low, this establishes a larger pressure gradient and thus a greater flow? But this seems counterintuitive since lowered radius of vessel = higher resistance, then shouldn't blood flow be slower instead of faster?
Thank you!
