Question

Explain how tubuloglomerular feedback and the juxraglomerular apparatus functions to regulate glomerular filtration rate.

Answer 1

Tubuloglomerular feedback is the principle mechanism to regulate glomerular filteration rate (GFR) and renal blood flow (RBF).

It is regulated with contribution of juxtaglomerular apparatus and macula densa it is a negative feedback regulatory mechansim which utilizes information regarding distal tubule flow rate which regulates the RBF and which is turn affects the GFR and distal tubule rate so it acts like a negative feedback to control or regulate both the things.

Do note that macula densa and juxtaglomerular cells are together known as juxtaglomerular apparatus.

Macula densa is a group of specialised epithelial cell which acts as a sensor present near loop of henle . It senses the tubular flow rate which is important for gfr regulation and sends it to the juxtaglomerular cells present in walls of afferent and efferent arterioles.

And juxtraglomerular cells got activated when macula senses tubular flow which causes reduction in GFR . for this as a response juxtaglomerular cells directly acts on the afferent arterioles to cause vasodilation and also secretes renin and activated angiotensin system and makes the vasoconstriction in renal efferent arterioles.

By this Co ordinated way the RBF gets adjusted in such a way that the GFR or glomerular capillary hydrostatic pressure gets increased and blood flows got increased due to decrease in the resistance and backup of the blood flow.

So by this process tubuloglomerular feedback and juxtaglomerular apparatus regulated the GFR.