Juxtaglomerular apparatus is involved in regulation of-
Ans. is 'a' i.e., Tubulo-glomerular feed back Tubulo-glomerular feedbacko To perform the function of autoregulation, the kidneys have a feedback mechanism that links changes in sodium chloride concentration at the macula densa with the control of renal arteriolar resistance. This feedback helps to ensure a relative constant delivery of sodium chloride to the distal tubule and helps prevent spurious fluctuations in renal excretion that would otherwise occur.o The tubuloglomerular feedback mechanism has two components that act together to control GFR : - i)An afferent arteriolar feedback mechanism (usually this component is referred to as tubuloglomerular feedback, and ii) An efferent arteriolar feedback mechanism.o These feedback mechanisms depend on the juxtaglomerular apparatus which consists of: (i) Macula densa, i.e., specialized epithelium of distal tubule where it comes in contact with afferent arteriole, (ii) Juxtaglomerular cells, i.e., modified smooth muscle cells of afferent arteriole, and (iii) Lads cells.i) Afferent arteriolar feedback mechanism :# Decrease in renal arteriolar pressure causes decrease in GFR and as a result low NaCl is delivered to distal tubules. This is sensed by macula densa and the signal is transmitted to afferent arterioles which causes decreased resistance of afferent arterioles. Decreased afferent arteriolar resistance increases glomerular hydrostatic pressure and therefore GFR.# The transmitter involves is adenosine which causes opening of Ca+2 channels.ii) Efferent arteriolar feedback mechanism :# Decreases GFR causes delivery of less NaCl to distal tubule, which is sensed by macula densa cells and the signal is transmitted to juxtaglomerular (JG) cells which secrete renin. As a result renin angiotensin system is activated and there is generation of angiotensin II which causes constriction of efferent arteriole. This results in increased glomerular capillary hydrostatic pressure and increased GFR.o It would be wise to know about glomerulotubular balance, which may be confused by tubuloglomerular feedback.o Glomerulotubular balance : - Tubular reabsorption in proximal tubules is load-dependent, i.e., when the GFR increase, the reabsorption of the filtrate in the proximal tubule increases proportionately. It occurs because tubular reabsorption is flow-limited. Because of glomerulotubular balance, the urinary Na+ output does not increase massively when the GFR increases.
Tubulo-glomerularfeedback
Glomerulotubular balance
Renal plasma flow
Urinary acidification
Glomerular Filtration, Renal Blood Flow, and Their Control