Second, renal autoregulation cannot compensate for extreme blood pressure variations Sympathetic Control Sympathetic nerve fibers richly innervate the renal blood vessels. It raises blood pressure by widespread vasoconstriction. It constricts the efferent arterioles and prevents the glomerular blood pressure from dropping too low. It increases tubular reabsorption of water, it stimulates the secretion of aldosterone, and stimulates the sense of thirst. While the glomerular capillaries are filtering the plasma, the peritubular capillaries are engaged in tubular reabsorption.
Water is reabsorbed by osmosis and carries other solutes along by solvent drag.
The PCT reabsorbs a greater variety of chemicals than any other part of the nephron. Some pass through the cytoplasm of the cell via the transcellular route, while others slip between epithelial cells using a paracellular route Tubular Secretion Tubular secretion is a process in which the renal tubule extracts chemicals from the capillary blood and secretes them into the tubular fluid. Tubular secretion serves the purposes of waste removal and acid-base balance. The primary purpose of the nephron loop is to enable the collecting duct to concentrate the urine. A distinguishing feature of these parts of the renal tubule is that they are subject to hormonal control.