Moslem Doctor wrote:
function curve

when TPR increase both venous return and CO decrease , like BRS said and Mean pressure is same


coz MAP=CO X TPR if keeping MAP constant and tpr incresed CO has to be dec.to maintain given pressure in other way,TPR incresed(arteriole constricts,making difficult for blood to flow from art to venous system hence less venous blood hence less CO.


so why when there is bleeding we say sympathetic activity increase and constrict veins(decrease the compliance ) so venous return increase and CO , why we dont mention that also TPR also increase in bleeding and this must make CO and VR decrease

in this case, bleeding causes dec co and MAP,to maintain it sympathetic (compensatory) dicharges which Inc TPR,acc- MAP=CO XTPR,to maintain MAP,if co is decresed other vairable should increase,thats TPR.VFC shifts to the left.

and CO is increased via renin system,low co,low kidney perfusion pressure,renin released(also direct sympathetic can stimulate beta receptor releasing renin)-->ATII-->aldosterone--na retention-->inc blood vol-->in co.