Understand the function of kidney

Hyderabad: This article is in continuation to the previous articles that focused the excretory system of living beings. REGULATION OF KIDNEY FUNCTION • The functioning of the kidneys is efficiently monitored and regulated by hormonal feedback mechanisms involving the hypothalamus, JGA and to a certain extent, the heart. • Osmoreceptors in the body are activated […]

Hyderabad: This article is in continuation to the previous articles that focused the excretory system of living beings.

REGULATION OF KIDNEY FUNCTION

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• The functioning of the kidneys is efficiently monitored and regulated by hormonal feedback mechanisms involving the hypothalamus, JGA and to a certain extent, the heart.
• 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 receptors which stimulate the hypothalamus to release antidiuretic hormone (ADH) or vasopressin from the neurohypophysis.
• ADH facilitates water reabsorption from latter parts of the tubule, thereby preventing diuresis.

• An increase in body fluid volume can switch off the osmoreceptors and suppress the ADH release to complete the feedback.
• ADH can also affect the kidney function by its constrictory effects on blood vessels.
• This causes an increase in blood pressure. An increase in blood pressure can increase the glomerular blood flow and thereby the GFR.
• The JGA plays a complex regulatory role.

• A fall in glomerular blood flow/glomerular blood pressure/GFR can activate the JG cells to release renin which converts angiotensinogen in blood to angiotensin I and further to angiotensin II.

• Angiotensin II, being a powerful vasoconstrictor, increases the glomerular blood pressure and thereby GFR.

• Angiotensin II also activates the adrenal cortex to release Aldosterone.
• Aldosterone causes reabsorption of Na and water from the distal parts of the tubule.

• This also leads to an increase in blood pressure and GFR.
• This complex mechanism is generally known as the Renin-Angiotensin mechanism.

• An increase in blood flow to the atria of the heart can cause the release of Atrial Natriuretic Factor (ANF).

• ANF can cause vasodilation (dilation of blood vessels) and thereby decrease the blood pressure.

• ANF mechanism, therefore, acts as a check on the renin-angiotensin mechanism.