Question

What causes granular cells to release renin?

Select increase or decrease:

a) Parasympathetic nervous system activity

b) Sympathetic nervous system activity

c) Plasma Osmolarity

d) GFR

e) Pressure in afferent arteriole

f) Filtrate Osmolarity

Answer 1

Renin is a hormone produced by the kidney. The granular cells of juxtaglomerular complex are responsible for release of renin.
Number of intrinsic and extrinsic factors help regulate the release of renin.
a) decreased parasympathetic activity stimulates renin secretion.
b) increased parasympathetic activity stimulates the secretion of renin.   
c) High plasma osmolarity.
when the plasma osmolarity is high that is when more amount of NaCl is present in the plasma that is entering the kidney, the granular cells are stimulates to increase renin production whixh help increase sodium reabsorption.
d) Decreased GFR

glomerular filtration rate is the rate of amount of fluid filtered by the kidneys.
A decreased GFR is sensed by the mechanoreceptors in the kidney and stimulates release of renin from granular cells.   
e) Increased filtrate osmolarity

When the filtrate passing through the renal tubules have a higher osmolarity it means that the content of NaCl is high in the filtrate. This indicates that less amount of sodium is being reabsorbed by the kidney. High concentration of sodium in filtrate stimulates renin release and results in increased sodium reabsorption.