Regional reaction types of the resistance vessels

Changes in regional blood distribution at various stimuli were studied in rats by using the "indicator fractionation technique" for measuring the cardiac output. Zones of preferential constriction of the resistance vessels, depending on the character and intensity of stimulation, were determined. The non-specific component of regional blood distribution depends on preferential constriction of the arteries of the area supplied by the abdominal aorta and of certain regions of the skin; skin + skeletal muscles; and of the majority of splachnic + skin regions. However, certain blood redistributions do not depend on typical regional reactions of the resistance vessels. At a mild blood loss during fixation stress and peritonitis there occurs predominantly a blood flow drop in the lungs, the myocardium and the liver. A diminution in the muscle fraction of cardiac output occurs also at the end of pregnancy and on the first days after delivery.