# STUCTURE OF ADH or VASOPRESSIN :
* ADH is a polypeptide containing nine amino acids .
* ADH is similar to Oxytocin because Oxytocin also contains nine amino acids.
* ADH and Oxytocin differs by only two amino acids.
#REGULATION OF ADH OR VASOPRSSIN SECRETION :
* Hypothalamus has median preoptic nucleus which is connected with medula and osmoreceptors present in brain.
* Median Preoptic nucleus can be stimulated in the following conditions :
1) When the blood pressure and volume decreases which is sensed by medula and passed onto median pre optic nucleus.
2) When the blood becomes hyperosmolar which is sensed by osmoreceptors and passed onto median preoptic nucleus.
* As median preoptic nucleus is stimulated , it eventually stimulates supraoptic nucleus to release ADH or vasopressin.
# ACTIONS OF ADH OR VASOPRESSIN ON KIDNEY :
* Low concentration of vasopressin can effectively act on Kidneys.
* There are vasopressin or ADH receptors on the cells of last part of nephron (distal convoluted tubule and collecting duct ).
* In the presence of vasopressin these receptors get activated and leads to phosphorylation of protein having aquaporins .
* When these proteins containing aquaporins are phosphorylated , the water pores or Aqua porins get embedded into the luminal membrane of the DCT and collecting duct cells.
* These water pores increase the water reabsorption from the tubular fluid making urine concentrated.
* Along with water, sodium also gets reabsorbed.
* ADH or vasopressin leads to retention of salt and water.
* Which increases blood pressure and blood volume.
#ACTIONS OF ADH OR VASOPRESSIN ON BLOOD VESSELS :
*To act on blood vessels the concentration of ADH must be more.
* Vascular smooth muscles have V1 receptors on them.
* ADH binda to this V1 receptors.
* Which leads to activation of receptors and increase in intracellular calcium and activation of contractile proteins.
* As intracellular calcium increases vascular smooth muscle contracts and
blood pressure increases.
# DIABETIS INSIPIDUS :
* There are of two types :
1) NEPHROGENIC DIABETIS INSIPIDUS :
* In this condition ADH production from supraoptic nucleus is normal.
* But the cells of distal convoluted tubule and collecting duct don't respond to ADH.
* This condition occurs when their are some renal diseases which leads to damage to last part of nephron.
2) CRANIAL DIABETIS INSIPIDUS :
* In this condition where the ADH production is very low.
* This may be due to to injury to
hypothalamus.
*The person passes very dilute urine . * Even though the DCT and convoluted tube are perfectly normal.
# SIADS ( syndrome of of inappropriate ADH secretion)
* In this condition there may be e some tumor in lungs which releases ADH excessively.
* This ADH acts on DCT and collecting duct and leads to retention of water.
* The person always passes concentrated urine.
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