ADH
Biology: AQA A Level, topic 6.4.10
Antidiuretic Hormone
Antidiuretic hormone (ADH) controls osmoregulation. ADH influences the permeability of the distal convoluted tubule and collecting duct. This controls how much water is reabsorbed from the kidney into the blood.
Hypothalamus
- Osmoreceptors in the hypothalamus (a section of the brain) monitor blood water potential.
- If the water potential increases, water diffuses into the osmoreceptor cells and the cells swell.
- If the water potential decreases, water diffuses out of the osmoreceptor cells and the cells shrink.
Posterior pituitary gland
- When osmoreceptors shrink, this is detected by the posterior pituitary gland.
- The posterior pituitary gland then releases ADH into the blood.
ADH
- ADH is a hormone that binds to receptors on the cell membrane of epithelial cells of the distal convoluted tubule (DCT) and the collecting duct.
- When ADH binds, vesicles containing aquaporins fuse with the cell membrane.
- Aquaporins are protein channels for water.
- Aquaporins increase the permeability of the DCT and collecting duct.
- This means that more water is reabsorbed into the blood by osmosis.
Urine
- If more ADH is in the bloodstream, more water is reabsorbed from the nephron into the blood.
- So the urine is more concentrated.
- If less ADH is in the bloodstream, less water is reabsorbed from the nephron into the blood.
- So the urine is more diluted.
Test yourself on ADH
What are the protein channels called that increase the permeability of the DCT and collecting duct?
Which of the following statements about ADH are true?
What happens to the urine when there is less ADH in the bloodstream?