Question

Outline the regulation of water and sodium balance by illustrating the response of the Renin-Angiostensin system to a decrease in blood volume. Use a block diagram to illustrate your answer.

Answer 1

Renin -angiotensin or renin -angiotensin -testosterone system ;

it helps in regulating the fluid balanceand blood pressure in the body.if the renin angiostensin system is abnormally active it leads to the high blood pressure .the system is activated when there is a loss of blood volume or drop in blodd pressure . the loss of blood prssure is detected by the baro receptors which are present in the carotid sinus . decreased NaCl concentration or decreased flow rate will result in stimulate muscula densa to stimulate relase of renin.

process ;

1. the juxtamuscular apparatus in the kidneys perfusion macula densa decreases ,then the cells release the enzyme renin
2. renin cleaves the zymogen which is a inactive form of angostensin to produce angiotensin 1
3. angiostensin 1 is converted into angiostensin 2by angiotensin converting enzyme in lung capillaries
4. this bind to the receptors on mesenglial cells ,causing them to contract along to release the aldosterone .angiostensin act as paracrine ,endocrine ,and intracrine hormone .

cardiovascular function ;

1. angiostensin 2 is a vasoconstrictor of arterioles ,they have greater effect on effrent than afferent arterioles
2. angiotensin 2 decreases the medullary blood flow through the vasa recta ,this decreases the washout of Nacl form the kidney space
3. it also stimulates Na +/H+ exchangers ,helps in sodium resorbtion in the loop of henle
4. it causes the release of aldostrone from the adrenal cortex ,which in Distal convoluted tubule releases the reabsorb more sodium ions and water form the urine ,this increases the blood volume and increases the blood pressure
5. these all togather act as increase the blood volume pressure

BP Decrease Increase →|Vasoconstriction|- AII ANP Aldosterone