How ADH tunes your urine

Science · The Human Body · ages 17-18

Name ______________________ Date ____________

Which kidney structure changes its water permeability in the ADH response taught here?
- The filtration barrier in the glomerulus
- The muscular wall around the renal artery
- The wall of the kidney's collecting duct
What does ADH stand for, and what is its water-balance role?
- Antidiuretic hormone; reduces water loss in urine
- Adrenal duct hormone; raises filtration pressure
- Active diffusion hormone; pumps water up its gradient
With healthy kidneys and other conditions unchanged, a rise in ADH usually makes urine more concentrated.
Circle one: True False
A normally hydrated person with healthy kidneys drinks a litre of water. After absorption, blood water potential rises. What urine change is expected?
- A smaller urine volume with a higher solute concentration
- No urine forms until all the extra water has entered body cells
- A larger volume of urine with a lower solute concentration
A salty meal lowers blood water potential. Which sequence links detection of this fall to extra ADH entering the blood?
- Osmoreceptors in the posterior pituitary detect it; collecting duct cells release ADH
- Osmoreceptors in the hypothalamus detect it; the posterior pituitary releases ADH
- Collecting duct cells detect it; the hypothalamus releases ADH into the urine
ADH makes the collecting duct more permeable to water. How does water then cross into the surrounding tissue fluid with a lower water potential?
- By osmosis down a water potential gradient
- By active transport that pumps water using ATP
- By pressure filtration at glomerular capillaries
Blood water potential falls, more ADH is released, and more water is reabsorbed. Why is this negative feedback?
- It keeps ADH release high once blood water potential returns towards normal
- It opposes the fall in blood water potential that triggered ADH release
- It lowers blood water potential further as water is returned to the blood
A student says, 'Less urine must mean less filtrate formed.' How can a rise in ADH reduce urine volume even if filtration stays the same?
- More filtered water is reabsorbed in the collecting duct
- Less filtered water is reabsorbed by kidney tubules
- More filtered water remains in the duct and leaves in urine

Answer key

For grown-ups. Fold this page away before handing over the rest.

How ADH tunes your urine W1-mt_Rz_MmL-Pa--s1

The wall of the kidney's collecting duct · ADH increases water permeability in the collecting duct wall by increasing water channels in its cells.
Antidiuretic hormone; reduces water loss in urine · ADH means antidiuretic hormone. A diuretic increases urine volume, while ADH's antidiuretic action reduces water loss in urine.
True · More ADH increases water reabsorption. Less water remains in the forming urine, so its solutes become more concentrated.
A larger volume of urine with a lower solute concentration · The rise reduces ADH release. The collecting duct becomes less permeable, so less water is reabsorbed and a larger volume of dilute urine forms.
Osmoreceptors in the hypothalamus detect it; the posterior pituitary releases ADH · Osmoreceptors in the hypothalamus detect the fall. The posterior pituitary releases more ADH into the blood.
By osmosis down a water potential gradient · Water crosses by osmosis into tissue fluid with a lower water potential. ADH increases water channels; it does not directly pump water.
It opposes the fall in blood water potential that triggered ADH release · Returning water raises blood water potential towards its usual range. This opposes the original fall and reduces the stimulus for ADH release.
More filtered water is reabsorbed in the collecting duct · Filtrate formation and water reabsorption are different steps. More ADH can return more filtered water to blood, leaving less to become urine.