What physiological change occurs to blood vessels during the mammalian dive reflex?

The mammalian dive reflex is a remarkable physiological response that occurs when a mammal's face is submerged in water. This reflex is particularly pronounced in marine mammals but is also present in humans and serves several critical functions during underwater breath-holding.

When the dive reflex is activated, blood vessels, particularly those in the peripheral areas of the body, constrict. This vasoconstriction reduces blood flow to the limbs and non-essential organs, preserving blood supply for vital organs such as the heart and brain. By prioritizing blood flow to these essential areas, the body can maintain core functions even in conditions where oxygen is limited. This is crucial in allowing mammals to conserve oxygen and increase survival time when submerged.

The other answer choices present alternatives that do not align with the physiological changes that occur during the mammalian dive reflex. For instance, blood vessels do not dilate to promote blood flow; instead, the opposite occurs during the dive reflex. Blood vessels are also not unchanged or expanded to lower heart rate; the heart rate may actually slow as a result of this reflex, but this is a separate response rather than a direct effect of blood vessel changes. Thus, the correct understanding of the dive reflex centers on the constriction of blood vessels to ensure that vital