original_query: What is tubuloglomerular feedback (TGF) and where does it occur within the kidneys?
query: What is tubuloglomerular feedback (TGF) and where does it occur within the kidneys?
answer: Tubuloglomerular feedback (TGF) is a feedback system within the kidneys that regulates glomerular filtration rate (GFR). It occurs within each nephron, specifically involving the interaction between the renal tubules and the glomerulus.  The macula densa, a group of cells in the tubular wall near the end of the thick ascending limb of the loop of Henle and the glomerulus, plays a central role in sensing chloride concentration and initiating the feedback response.