Question

An individual has a higher-than-normal blood volume, due to excess fluids—not high enough to cause symptoms, but enough to cause the body to attempt a restoration to normal levels. Also, it is stipulated that there are no ion imbalances present. Describe all processes by which the body induces the decrease of blood volume. Your response should include a review of all body cells and structures capable of detecting high blood volume, the body responses that stimulate fluid excretion, and all processes for the removal of fluids from the body.

Answer 1

When there is volume overload solely due to excess of water, this Increased volume is sensed by the walls of the right Ventricle which lead to secretion of Atrial Natutrtic Peptide (ANP) & Brain naturetic peptide.

ANP act on the Affernet arteriole of kidney and lead to Arteriolar dilation and hence Increases glomerular blood flow. This Increases Glomerular capillary hydrostatic pressure which is responsible for more Filtration and Increased GFR.

ANP also act upon the Collecting duct of nephron and prevent reabsorbtion of sodium from the nephron. Hence, with loss of Na in urine, water is also lost in urine, called as naturesis.

Both ANP and BNP inhibit the release of Renin. Hence the renin angiotensin aldosterone system decreses aldosterone. This reduced aldosterone further prevent salt and water reabsorption from the DCT. Hence more water is lost in the urine along with sodium. This is called as naturesis.

In this way the body returns it fluid balance.