Question

In tubuloglomerular feedback, an increase in glomerular filtration rate would increase the ________, thereby stimulating the release of a paracrine factor from the macula densa that would ________.

1) afferent arteriolar pressure : constrict the afferent arteriole
2) afferent arteriolar pressure : increase filtrate flow
3) flow of tubular fluid : dilate the afferent arteriole
4) flow of tubular fluid : constrict the efferent arteriole
5) flow of tubular fluid : constrict the afferent arteriole

Answer 1

An increase in glomerular filtration rate causes the flow of tubular fluid to increase, which triggers the macula densa to release paracrine factors that constrict the afferent arteriole, thus reducing the glomerular filtration rate.

Step-by-step explanation:

In tubuloglomerular feedback, an increase in glomerular filtration rate (GFR) leads to an increased flow of tubular fluid past the macula densa cells in the distal convoluted tubule (DCT). As a result, the high flow rate, along with higher osmolarity due to less time for NaCl reabsorption, leads to the release of ATP and adenosine from the macula densa cells. These act as paracrine factors that cause the afferent arteriole to constrict, thus, reducing the GFR back to normal levels.

Therefore, the final answer is that an increase in GFR would increase the flow of tubular fluid, thereby stimulating the release of a paracrine factor from the macula densa that would constrict the afferent arteriole. This response is a protective mechanism that ensures the kidney functions within a precise and optimal range, adapting to physiological changes and maintaining homeostasis.