Changes

==[[Pituitary Gland - Anatomy & Physiology #Posterior Pituitary Gland| ADH]] and the [[Reabsorption and Secretion Along the Distal Tubule and Collecting Duct - Anatomy & Physiology#Collecting Duct|Collecting Duct]]==

==[[Pituitary Gland - Anatomy & Physiology #Posterior Pituitary Gland| ADH]] and the [[Reabsorption and Secretion Along the Distal Tubule and Collecting Duct - Anatomy & Physiology#Collecting Duct|Collecting Duct]]==

[[Image:collductexch.jpg|right|thumb|200px|<small><center>Exchange in the Principal Cells of the Collecting Duct</center></small>]]

[[Image:collductexch.jpg|right|thumb|200px|<small><center>Exchange in the Principal Cells of the Collecting Duct</center></small>]]

The membrane of the [[Collecting Duct - Anatomy & Physiology|Collecting Duct]] is practically impermeable to water.  Therefore in order for water reabsorption from this part of the nephron to occur it is vital that aquaporins are inserted.  This is the role of [[Pituitary Gland - Anatomy & Physiology #Posterior Pituitary Gland| ADH]].  These channels are always present on the basolateral membrane of the epithelial cells but their presence and concentration on the apical membrane is reliant on the concentration of ADH in the blood. ADH works by binding to '''V₂''' receptors on the basolateral membranes of the cells and activates adenyl cyclase creating '''cyclicAMP''' (cAMP) this in turn activates '''protein kinase A''' which causes '''protein phosphorylation'''.  This causes vesicles with ready made glycoprotein '''AQP2''' aquaporins in their membranes to move to the apical cell membrane and insert the aquaporins via exocytosis.  This rapidly increases the water permeability and allowing reabsorption

The membrane of the [[Reabsorption and Secretion Along the Distal Tubule and Collecting Duct - Anatomy & Physiology#Collecting Duct|Collecting Duct]] is practically impermeable to water.  Therefore in order for water reabsorption from this part of the nephron to occur it is vital that aquaporins are inserted.  This is the role of [[Pituitary Gland - Anatomy & Physiology #Posterior Pituitary Gland| ADH]].  These channels are always present on the basolateral membrane of the epithelial cells but their presence and concentration on the apical membrane is reliant on the concentration of ADH in the blood. ADH works by binding to '''V₂''' receptors on the basolateral membranes of the cells and activates adenyl cyclase creating '''cyclicAMP''' (cAMP) this in turn activates '''protein kinase A''' which causes '''protein phosphorylation'''.  This causes vesicles with ready made glycoprotein '''AQP2''' aquaporins in their membranes to move to the apical cell membrane and insert the aquaporins via exocytosis.  This rapidly increases the water permeability and allowing reabsorption