Regulation of Kidney Function MCQ - Practice Questions with Answers

• 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.

Control by 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 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 constrictor 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.

Control by Juxtaglomerular Apparatus:

• 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 the 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-Aldosterone mechanism.

Control by ANF:

• 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.