Zoology - Excretory Products and their Elimination Question with Solution | TestHub

The juxtaglomerular cells ($\mathrm{JGC}$) secretes an enzyme rennin in response to a variety of stimuli such as decreased flow of filtrate and $\mathrm{NaCl}$ to macula densa, decrease in glomerular filtration rate ($\mathrm{GFR}$), decreased stretch of $\mathrm{JGC}$, and increased frequency of nerve impulses in the renal sympathetic nerves. 

Atrial Natriuretic Factor ($\mathrm{ANF}$) decreases blood pressure as it is a powerful vasodilator.

Angiotensin $\mathrm{II}$ is a powerful vasoconstrictor.

The counter-current mechanism involves the exchange of water and electrolytes between blood flowing in vasa recta and filtrate in Loop of Henle.