snímek PPT
The sodium appetite is rudimentary in Man, Na regulation is mediated by Na urinary excretion exclusively (feedback No. 2). Three ways:
- aldosterone: the renin secretion is a consequence
both of sympathetic activity and of declined
pressure in the afferent arteriole
- “third factor”: a.o., changes in the hydrostatic and oncotic pressures in the peritubular capillaries in hypervolemia and arterial hypertension ? ?Na, water and solute´s reabsorption ? pressure diuresis
The three feedback circuits regulating tonicity and volume work in concert of course and represent a certain redundancy of the regulation. They differ, a.o., by their dynamic lag. The definitive correction of volume is conditioned by proper functioning of the circuit No. 3, of course.