Role of splanchnic resistance vessels in overall cardiovascular homeostasis.

The reactions of splanchnic resistance vessels elicited reflexly from cardiovascular baroreceptors, volume receptors, and chemoreceptors are briefly reviewed. Unloading the baroreceptors and/or the volume receptors evokes a chiefly neurogenic constriction of resistance vessels in the splanchnic region. There is no significant change in the post- to precapillary resistance ratio to evoke any change in mean capillary hydrostatic pressure. In contrast, the post- to precapillary resistance ratio of the skeletal muscle vascular bed falls, thus lowering mean capillary pressure and causing an autotransfusion of the cardiovascular system. Stimulating the chemoreceptors induces vascular effects in the splanchnic organs and the skeletal muscle similar to that of unloading the baroreceptors. In hemorrhagic hypotension an integrated response from the different receptors is observed. No change occurs in the post- to precapillary resistance ratio in the splanchnic area even during prolonged hemorrhagic hypotension.