USMLE Vascular function curve confusion

[OphthLover]

This is such a mind-boggling concept, and I would greatly appreciate if someone could please clarify the confusion I am having.

On CV chapter of FirstAid, particularly on the "Cardiac and vascular function curves" page (pg 275 of 2015 ed), label on a vascular function curve indicates that the curve would shift upward if volume is added or venous tone is increased. The page also states that a vascular fuction curve would shift up in cases of fluid infusion or positive sympathetic activity.

Does the positive sympathetic activity refer to the increased venous tone? What confuses me is that sympathetic activity would lead to vasoconstriction (with exception of coronary and cerebral a.), which would increase TPR, which would then decrease vascular function curve (shifting it down). Can anyone please explain this seemingly contradictory information?

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[EmetyreUSMLEStep1Tutor1]

Does the positive sympathetic activity refer to the increased venous tone?
Yes it is. Veins are constricted - and because veins are the main storage hub for blood, blood just goes out of their hub - more fluid goes to heart - increased preload.

>What confuses me is that sympathetic activity would lead to vasoconstriction (with exception of coronary and cerebral a.), which would increase TPR, which would then decrease vascular function curve (shifting it down).
That is why you have third table on TPR and in the bottom of the page it is written
"Changes often occur in tandem, and may be reinforcing (e.g., exercise  inotropy and  TPR to maximize CO) or
compensatory (e.g., HF  inotropy Ž fluid retention to  preload to maintain CO)"