Question

At high levels of antidiuretic hormone (ADH), distal convoluted tubules and collecting ducts are _____ to H₂O, _____ urine is excreted

1. 	a.	impermeable, dilute
   	b.	permeable, concentrated

Answer 1

Option B-Permiable , Concentrated.

When you Have low Plasma Volume (High Osmolarity)or Low BP .It stimulates the release of Renin from the juxtaglomerular cells of Kidneys.

Renin acts on Angiotensiogen Released from the Liver & Converts Angiotensiogen(Inactive)----Angiotensin 1(Active).

Angiotensin Converting Enzyme(ACE) Acts on Angiotensin 1 and converts it into-----------Angiotensin 2.

Angiotensin 2 Stimulates -

1.Stimulates CNS to increase ADH( vasopressin) production from the Posterior Pituitary

2.Acts on venous and arterial smooth muscle which cause vasoconstriction.

3.Increases aldosterone secretion .

**ADH Acts on Collecting Duct------to the V2 receptors on the cell surface of tubular cells--- intracellular cascade that results in formation of water channel, aquaporin-2.---These water channels Increases permiabiltiy to Water.

So Through These water channels,There is Reabsorbtion of Water From The Filtrate(Urine) into the Interstitium then to Blood.So more of the water from Urine is Absorbed back into Blood so Urine Excreated will be Concentrated