What is the macula densa

This is a thickened region of ductal epithelia where the DCT passes close to the vascular pole of the glomerulus These cells sense rise in Na+ which leads to triggers the synthesis of adenosine which then triggers Ca2+ to be released which causes smooth muscle contraction in the afferent arterioles which restricts blood flow and leads to reduced Na+ conc which shuts of the vasoconstrictive signal