Urine Concentration Mechanisms

What happens in the descending limb of the Loop of Henle?

Water is reabsorbed, and the filtrate becomes more concentrated.

What happens in the ascending limb of the Loop of Henle?

Solutes are reabsorbed, and the filtrate becomes more dilute.

What happens in the DCT in the absence of ADH?

There is some solute reabsorption, but little to no water reabsorption.

How does the collecting duct (CD) function in the absence of ADH?

It is impermeable to water.

What is the effect of low ADH levels on urine concentration?

It leads to the production of dilute urine.

What is the effect of high ADH levels on urine concentration?

It leads to the production of concentrated urine.

What is the effect of diuretics on urine production?

Diuretics increase urine volume by inhibiting sodium reabsorption (caffeine) or inhibiting ADH secretion (alcohol).