NEUROGENIC ADJUSTMENTS OF MUSCLE BLOOD FLOW CUTANEOUS A-V SHUNT FLOW AND OF VENOUS TONE DURING DIVING IN DUCKS

The effect of “diving” on the vascular response in skeletal muscle, the web and the veins was studied in experiments on ducks. Muscle blood flow completely stopped during submersion due to neurogenic vasoconstriction of the resistance vessels, at the same time as the constrictor fibres to the systemic veins were excited. As a contrast, web blood flow changed only little during submersion, unless the duck was excited. In this latter case it decreased, whether the animal was submerged or not. The profound muscle vasoconstriction helps to conserve the oxygen stores for the “essential” tissues, the heart and the brain. The preserved web blood flow, on the other hand, primarily passes through A‐V shunts and, in conjunction with the venous constriction, it pushes blood from the considerable, oxygen‐containing venous depots to the heart without causing peripheral oxygen “losses” from the blood. Such mechanisms serve to make the total venous oxygen stores available for subsequent cardiac output to the brain and the myocardium. © 1969 Scandinavian Physiological Society