Autoregulation of glomerular filtration by tubuloglomerular feedback helps protect the kidney:
A) from rapid systemic arterial pressure variations that would otherwise cause large glomerular filtration rate changes.
B) from rapid systemic venous pressure variations that would otherwise cause large glomerular filtration rate changes.
C) by contracting the walls of the efferent arterioles, thus increasing systemic blood pressure.
D) by relaxing the walls of the efferent arterioles, thus reducing systemic blood pressure.

Question

Quizplus · Accepted Answer

Tubuloglomerular feedback (TGF) is a mechanism through which the juxtaglomerular apparatus (JGA) in the kidney senses changes in tubular flow and adjusts the resistance of the afferent arterioles. This helps maintain a relatively constant glomerular filtration rate (GFR) in the face of systemic arterial pressure variations. Specifically, when the GFR increases, there is an increase in fluid flow rate through the tubules. This leads to a higher concentration of NaCl in the distal tubule, which is detected by the macula densa cells in the JGA. The macula densa then signals the JGA to decrease the resistance of the afferent arterioles, thereby increasing renal blood flow and reducing the GFR. Conversely, when the GFR decreases, there is a decrease in fluid flow rate through the tubules, which leads to a lower concentration of NaCl in the distal tubule. This is also detected by the macula densa, which then signals the JGA to increase the resistance of the afferent arterioles, thereby decreasing renal blood flow and increasing the GFR. Overall, TGF helps prevent large fluctuations in GFR in response to systemic arterial pressure changes.

Autoregulation of Glomerular Filtration by Tubuloglomerular Feedback Helps Protect the Kidney