Kidney, nephron and ADH – osmoregulation
BiologyHuman & Animal PhysiologyAges 16–17
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Sign in to playA nephron filters blood in the glomerulus, reabsorbs useful substances in the proximal convoluted tubule, builds a salt gradient in the medulla with the loop of Henle (counter-current multiplier) and reabsorbs water in the collecting duct under the control of ADH and aquaporins. Change water intake, sweating, salt and protein to see blood osmolality, ADH, urine volume and urine concentration respond by negative feedback; compare a healthy person, untreated diabetes and kidney failure, and run a dialysis session (counter-current or same direction) compared with a kidney transplant.
Lesson: Osmoregulation and excretion: the kidney
What it shows
The kidneys remove urea and control the water and ion content of the blood. In each nephron, high pressure in the glomerulus forces small molecules into Bowman's capsule (ultrafiltration). The proximal convoluted tubule reabsorbs all the glucose and amino acids and most of the water and ions. The loop of Henle pumps ions into the medulla, so the collecting duct can reabsorb water by osmosis. When the blood is too concentrated, osmoreceptors in the hypothalamus trigger the release of ADH from the posterior pituitary; ADH adds aquaporins to the collecting duct, so less, more concentrated urine is made. This is negative feedback.
How to use
In Kidney and nephron, use Zoom to move from the urinary system to the kidney and one nephron, and tap a part to read what it does. In Water balance and ADH, change Drinks, Salt, Protein and Weather, or press Drink 1 L of water, Salty snack or Exercise 1 h, and watch the graphs. Switch Person to compare. In Dialysis and transplant, press Start session, then Record result, and try the other Fluid flow.
Parameters you can change
- Screen Kidney and nephron, Water balance and ADH, Dialysis and transplant
- Person Healthy, Untreated diabetes, Kidney failure
- Drinks 0.5–5 L/day
- Salt 1–20 g/day
- Weather Cool (little sweating), Warm day, Hot day
- Protein in the diet 40–150 g/day
- Dialysis fluid flow Counter-current, Same direction
Questions to explore
- Why does drinking 1 L of water produce a large volume of dilute urine?
- Why does a person with untreated diabetes have glucose in the urine and feel thirsty?
- Why does counter-current flow remove more urea in the dialyser than flow in the same direction?
