1.Example of humoral regulation – PTH
PTH (parathyroid horm.) is secreted by Parathyroid glands.
The calcium receptor(sensor) in the parathyroid gland cell detects changes in the ECF calcium concentration.
When ECF calcium is high, calcium binds to the receptor and this inhibits PTH secretion.
When ECF calcium is low, the receptor is unbound and so there is no inhibition and PTH secretion occurs.