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I'm not sure what the mechanism is, but the nurse is only partially right. An increase in pCO2 causes vasoconstriction in the pulmonary vasculature and vasodilation EVERYWHERE else. CO2 causes constriction in the pulmonary vasculature because an increase in pC02 sends the message there is damage/shunting here, sending blood here will not effectively oxygenate it so blood is preferentially sent to a different part of the lung where it will receive better oxygenation.
The blood vessels of skeletal muscles, in contrast, has beta 2 receptors which causes vasodilation. Hence sympathetic stimulation cause vasoconstriction of blood vessels of viscera and dilates the vessels of skeletal muscles redirecting blood flow to skeletal system, thus preparing for fight, flight, fright reaction.The heart rate also increases, forcing more blood to flow to muscles.Hope this helps :).ut at the same time they cause vasoconstriction of arteries carrying blood to the digestive organs, kidneys, and all those other internal organs that are not necessary for short-term survival (which is what the sympathetic system is all about).