How is the function of the kidney regulated?

(N/A) The functioning of the kidneys is regulated by hormonal feedback mechanisms involving the hypothalamus,$JGA$,and the heart.
$(1)$ Hypothalamus: Osmoreceptors in the body are activated by changes in blood volume,body fluid volume,and ionic concentration. An excessive loss of fluid from the body activates these receptors,which stimulate the hypothalamus to release antidiuretic hormone $(ADH)$ or vasopressin from the neurohypophysis.
- $ADH$ facilitates water reabsorption from the latter parts of the tubule,thereby preventing diuresis.
- An increase in body fluid volume can switch off the osmoreceptors and suppress $ADH$ release to complete the feedback.
- $ADH$ also affects kidney function by its constrictory effects on blood vessels,increasing blood pressure,which in turn increases glomerular blood flow and $GFR$.
$(2)$ Renin-Angiotensin mechanism $(RAAS)$: The $JGA$ plays a complex regulatory role. $A$ fall in glomerular blood flow,glomerular blood pressure,or $GFR$ activates the $JG$ cells to release renin.
- Renin converts angiotensinogen in the blood to angiotensin $I$ and further to angiotensin $II$.
- Angiotensin $II$,being a powerful vasoconstrictor,increases glomerular blood pressure and thereby $GFR$.
- Angiotensin $II$ also activates the adrenal cortex to release aldosterone,which causes reabsorption of $Na^+$ and water from the distal parts of the tubule,leading to an increase in blood pressure and $GFR$.
$(3)$ Atrial Natriuretic Factor $(ANF)$: An increase in blood flow to the atria of the heart causes the release of $ANF$.
- $ANF$ causes vasodilation (dilation of blood vessels),which decreases blood pressure and acts as a check on the $RAAS$ mechanism.