Question

If the diameter of the afferent arteriole is smaller than the diameter of the efferent arteriole:

W. The net filtration pressure will decrease.
X. blood pressure in the glomerulus will decrease.
Y. GFR will decrease.
Z. Urine production will increase.

Answer 1

A smaller afferent arteriole diameter compared to the efferent arteriole would result in decreased GFR, leading to reduced urine production due to lower blood pressure and net filtration pressure in the glomerulus.

Step-by-step explanation:

The student asked what would happen if the diameter of the afferent arteriole is smaller than the diameter of the efferent arteriole. It's important to understand that the Glomerular Filtration Rate (GFR) is strongly influenced by the diameters of these arterioles. The afferent arteriole is responsible for supplying blood to the glomerulus, whereas the efferent arteriole drains the blood away. In the case that the afferent arteriole has a smaller diameter than the efferent arteriole, less blood would enter the glomerulus, leading to a lower GFR.

According to the autoregulation mechanisms within the kidneys, specifically the myogenic mechanism and the tubuloglomerular feedback, a decrease in afferent arteriole diameter would cause a series of responses. This condition would not only decrease the blood pressure in the glomerulus, but also decrease the net filtration pressure. As a result, GFR would decrease, leading to less urine being produced, contrary to the idea that urine production would increase.

Answer 2

Decreasing the diameter of the afferent arteriole, compared to the efferent arteriole, reduces blood flow to the glomerulus, leading to a decreased glomerular filtration rate (GFR), and consequently, less urine production.

Step-by-step explanation:

When analyzing kidney function, specifically within the dynamic process of glomerular filtration, a key concept to understand is the role of arteriole diameter in regulating Glomerular Filtration Rate (GFR). If the diameter of the afferent arteriole is smaller than the diameter of the efferent arteriole, this constricted afferent arteriole would lead to a reduced blood flow into the glomerulus. Consequently, this would lead to a decrease in the glomerular blood pressure and filtration pressure, resulting in a lowered GFR.

Therefore, less filtration means the kidneys produce less urine. Contrasting scenarios including various vasodilation and vasoconstriction effects are regulated by autoregulatory mechanisms such as the myogenic mechanism and the tubuloglomerular feedback mechanism, which maintain a relatively consistent GFR despite systemic blood pressure changes. These complex interactions between systemic blood pressure and kidney function highlight the delicate balance needed to maintain homeostasis within the body.

Based on the given mechanisms related to kidney function, the correct option when the diameter of the afferent arteriole is smaller than that of the efferent arteriole would be 'Y. GFR will decrease.'