During fight and flight response, elevated levels of epi and norepi stimulate less sensitive alpha receptors and beta receptors on smooth muscle of blood vessels. How does this impact blood flow?

Answer 1

Epinephrine and norepinephrine increase peripheral resistance. This means that they cause peripheral blood vessels to constrict which reduces blood flow in general.

Answer 2

When a human initiates the fight or flight response (sympathetic nervous response), blood is shunted from the internal organs into the peripheral muscle tissue to allow the person to perform athletic tasks to get away from the predator. Think about our ancestors, they had to run from wild animals in order to survive. Thus vasodilation happens in the peripheral muscles and vasoconstriction happens in the organ blood supply to allow this shunting of blood to happen.

Another way to think about it is that the body is prioritizing its needs at the moment. What would be more important- digesting the sandwich you ate for lunch or running away from a lion that is trying to eat you for lunch?

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