True about Macula Densa is/are:
Also known as Tubulo glomerular feedback.
Macula densa senses change in NaCl concentration.
For autoregulation of GFR.
All of the above.
Function of Macula Densa (Tubulo glomerular feedback): 

Macula densa senses change in NaCl concentration. 
For autoregulation of GFR.