Question

question 17 (0.5 points)
what happens when high blood pressure causes afferent arterioles to stretch?

1. they dilate causing a decrease in glomerular capillary hydrostatic pressure.
2. they constrict (smooth muscle in blood vessel contracts) causing a decrease in glomerular capillary hydrostatic pressure.
3. they constrict causing an increase in glomerular capillary hydrostatic pressure.
4. they dilate causing a decrease in glomerular capillary oncotic pressure.

Explanation:

To solve this, we analyze the renal autoregulation mechanism. When high blood pressure stretches afferent arterioles, the myogenic mechanism is triggered. The smooth muscle in the afferent arteriole contracts (constricts) to resist the stretch. This constriction reduces blood flow into the glomerulus, decreasing glomerular capillary hydrostatic pressure. Let's evaluate each option:

• Option 1: Afferent arterioles do not dilate in response to stretch from high BP; they constrict, so this is incorrect.
• Option 2: Correct. The myogenic response causes constriction (smooth muscle contraction) of afferent arterioles, reducing glomerular capillary hydrostatic pressure to maintain GFR.
• Option 3: Constriction would decrease, not increase, hydrostatic pressure, so this is incorrect.
• Option 4: Dilation is not the response, and oncotic pressure is related to solute concentration, not arteriole stretch response, so this is incorrect.

Answer:

The correct option is: They constrict (smooth muscle in blood vessel contracts) causing a decrease in glomerular capillary hydrostatic pressure. (The second option in the list of choices)