Q.Discuss the hormonal regulation of kidney function, covering the renin-angiotensin-aldosterone system, atrial natriuretic factor (ANF), and ADH, and explain what diabetes insipidus is and why it occurs.

[!TLDR]

RAAS (JGA->renin->angiotensin II->aldosterone) raises BP when low; ANF (from the heart's atria) lowers it when high; ADH concentrates urine by controlling DCT/collecting-duct water permeability; ADH deficiency = diabetes insipidus. …

Kidney function is regulated by three linked hormonal mechanisms. The renin-angiotensin-aldosterone system (RAAS) is triggered when the juxtaglomerular apparatus (JGA) senses a fall in glomerular blood flow or blood pressure; its juxtaglomerular cells then release renin, which converts plasma angiotensinogen (from the liver) into angiotensin I, which is in turn converted, chiefly in the lungs, into angiotensin II by angiotensin-converting enzyme (ACE). Angiotensin II is a powerful vasoconstrictor that directly raises blood pressure, and it also stimulates the adrenal cortex to secrete aldosterone, which promotes Na+ (and, following it, water) reabsorption at the DCT, raising blood volume and further raising blood pressure -- so RAAS as a whole restores blood pressure and GFR toward normal whenever they have fallen too low.

Atrial natriuretic factor (ANF) provides an opposing check on this system. It is secreted by the muscular walls of the atria of the heart when they are stretched by an excessive rise in blood volume, and it causes vasodilation and increases Na+ and water excretion by the kidney, both lowering blood volume and blood pressure -- the direct physiological opposite of RAAS, keeping blood pressure from drifting too far in either direction.

ADH (antidiuretic hormone, vasopressin), produced by the hypothalamus and released from the posterior pituitary, is secreted separately in response to a rise in blood osmolarity or a fall in blood volume. It increases the permeability of the DCT and, especially, the collecting duct to water, allowing more water to be reabsorbed as tubular fluid passes through the medullary osmotic gradient, producing a smaller volume of more concentrated urine and helping restore normal blood osmolarity. …

Cover the three regulatory systems in turn, each with its trigger/stimulus, its source, its mechanism of action, and its net effect: RAAS (raises BP when low), ANF (lowers BP when high, opposing RAAS), and ADH …

Presenting RAAS and ANF as unrelated systems rather than explicitly noting that they act as opposing checks on each other, or omitting the specific link between A …