Final answer:
Angiotensin II causes efferent arteriole vasoconstriction to regulate blood pressure by reducing glomerular filtration rate and renal blood flow.
Step-by-step explanation:
Angiotensin II (AngII) causes efferent arteriole vasoconstriction as part of its role in regulating blood pressure. When there is a decrease in blood pressure, AngII is released and acts systemically to constrict the arterioles. By constricting the efferent arteriole, AngII reduces both glomerular filtration rate (GFR) and renal blood flow, which helps limit fluid loss and preserve blood volume. This process helps maintain adequate blood pressure.