Regulation of Kidney Function ; Antidiuretic hormone ( ADH) ,(JGA) ,(ANF).

 Regulation of Kidney Function

The functioning of the kidneys is efficiently monitored and regulated by a hormonal feedback mechanism involving the hypothalamus (ADH). JGA and to a certain extent, the heart (ANF).

Antidiuretic hormone (ADH)

 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 can activate these specific receptors which stimulate the hypothalamus to release antidiuretic hormone (ADH) or vasopressin from the neurohypophysis. ADH facilitates water reabsorption by the distal parts of the kidney tubule, thereby preventing diuresis. An increase in body fluid volume can switch o the osmoreceptors and suppress the ADH release to complete the feedback ADH can also affect the kidney function by the constriction of blood vessels, thus causing an increase in blood pressure which can increase the glomerular blood flow and thereby GFR.

Drugs (called diuretics) increase the production of diluté urine and prevent excessive water retention and tissue swelling (edema).
Alcohol inhibits the release of ADH, while caffeine interferes with ADH action and sodium reabsorption thus, both these increase the loss of water in urine.
Due to the deficiency of ADH, a disease called diabetes insipidus is caused in which the output of urine may reach 20-25 liters/day.

Juxtaglomerular Apparatus (JGA)

As blood flows glomerular blood pressure, GFR decreases, JG cells of the juxtaglomerular apparatus activate to release the enzyme renin. Renin converts angiotensinogen in the blood into angiotensin I and then into angiotensin Il.

Angiotensin ll has the following effects:

Haise's glomerular blood pressure and thereby GFR by constricting blood vessels as it is a powerful vasoconstrictor.

Stimulates adrenal cortex to release aldosterone.

Aldosterone causes sodium and water reabsorption by the distal part of the tubules. This also leads to an increase in blood pressure and GFR: This complex mechanism is generally known as the Renin-Angiotensin mechanism.

Atrial natriuretic factor (ANF)

An increase in blood flow to the atria of the heart can cause the release of the Atrial Natriuretic Factor (ANF). ANF can cause vasodilation (dilation of blood vessels and thereby decrease the blood pressure ANF inhibits the release of re IGA and acts as a check on the renin-angiotensin mechanism.

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