Where is ADH made? Where is it released?
Magnocellular neurons of hypothalamus.
Released from posterior pituitary
Where is the primary site of ADH's actions?
Principle cell in the distal tubule of the kidney
What cellular mechanisms are activated by ADH?
What stimulates ADH's release?
Increased blood osmolarity, blood loss, pain, emotional stress, nausea, vomiting, heat, drugs
What inhibits ADH's release?
Alcohol, cortisol, thyroid hormone
What is ADH's half life?
What are the two mechanisms by which ADH is released?
1) Increase in plasma tonicity: stimulates hypothalamic osmoreceptors and magnocellular neurons to shrink, signaling magnocellular neurons to release ADH; sharp spike in ADH when plasma osmolarity reduces to between 285-295mOsm/kg; **ADH is released WAY BEFORE you start to feel thirsty;
2) Decrease in MABP (blood loss) --> causes decreased baroreceptor stretch and firing (IX and X) --> causes sympathetic tone to increase --> further increasing ADH release. This mechanism also makes mechanism 1 more sensitive