Figure 19-1 shows the approximate average effect of different arterial pressure levels on urinary volume output by an isolated kidney, demonstrating markedly increased output of volume as the pressure rises. This increased urinary output is the phenomenon of pressure diuresis. The curve in this figure is called a renal urinary output curve or a renal function curve. In the human being, at an arterial pressure of 50 mm Hg, the urine output is essentially zero. At 100 mm Hg it is normal, and at 200 mm Hg it is about six to eight times normal. Furthermore, not only does increasing the arterial pressure increase urine volume output, but it causes approximately equal increase in sodium output, which is the phenomenon of pressure natriuresis.
An Experiment Demonstrating the Renal-Body Fluid System for Arterial Pressure Control. Figure 19-2 shows the results of a research experiment in dogs in which all the nervous reflex mechanisms for blood pressure control were first blocked. Then the arterial pressure was suddenly elevated by infusing about 400 milliliters of blood intravenously. Note the instantaneous increase
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.