Kidneys and BP

[Adnama]

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Can someone explain the relationship between osmolarity of urine/ extracellular fluids to the kidney.

How is this related to osmostic/hydrostatic pressure.

For example: Increased ADH causes decreased urine volume (makes sense)... and increased extracellular fluid volume, and decreased extracellular osmolarity. I don't get it

 

[xIcewind]

Are you referring to when the hormone acts to preserve water, it drives up the pressure in the loops of henle, thus prompting the fluids from the loops into the surrounding tissue?

It's been a bit since I took Biology, but is that what you're asking?

 

[amar21]

Can someone explain the relationship between osmolarity of urine/ extracellular fluids to the kidney.

How is this related to osmostic/hydrostatic pressure.

For example: Increased ADH causes decreased urine volume (makes sense)... and increased extracellular fluid volume, and decreased extracellular osmolarity. I don't get it

They must be referring to ECF as being the blood plasma... thus increasing blood volume and furthermore decreasing blood osmolarity (more dilute). (and presure also increases!)

EDIT: I'll explain it better... the point of ADH is to retain more water. So if you understand that by retaining more water you are excreting less urine, it only makes sense that water is being put back into the body and thus your ECF goes up.

 

[Instatewaiter]

Can someone explain the relationship between osmolarity of urine/ extracellular fluids to the kidney.

How is this related to osmostic/hydrostatic pressure.

For example: Increased ADH causes decreased urine volume (makes sense)... and increased extracellular fluid volume, and decreased extracellular osmolarity. I don't get it

ADH acts on the collecting ducts of the kidneys by increasing the # of aquaporins. It also constricts BVs (a smaller action) So, more water comes out of the tubules and thus there is less water in the urine. Less water in the urine means 1) there is concentrated urine and 2) there is more water in the body. More water in the body means the plasma osmolarity goes down.

Thus, more water in the body dilutes the plasma osmolarity. The increase in volume causes an increase in the pressure. Thus you see an increase in BP. Note that ADH (aka vasopressin) also constricts vasculature which further increases BP.

 

[Adnama]

ADH acts on the collecting ducts of the kidneys by increasing the # of aquaporins. It also constricts BVs (a smaller action) So, more water comes out of the tubules and thus there is less water in the urine. Less water in the urine means 1) there is concentrated urine and 2) there is more water in the body. More water in the body means the plasma osmolarity goes down.

Thus, more water in the body dilutes the plasma osmolarity. The increase in volume causes an increase in the pressure. Thus you see an increase in BP. Note that ADH (aka vasopressin) also constricts vasculature which further increases BP.

Thank you!!

what is plasma osmolarity exactly?

 

[amar21]

solute concentration in the plasma