Sympathetic stimulation of the muscular walls of arterioles and veins causes vasoconstriction. Considering that the circulatory system in vertebrates is a closed system (i.e. normally all blood is contained in blood vessels), explain why animals can get by with having arterioles and veins innervated by the sympathetic nervous system without antagonistic innervation by the parasympathetic nervous system.

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The Answer of Sympathetic stimulation of the muscular walls of arterioles and veins causes vasoconstriction. Considering that the circulatory system in vertebrates is a closed system (i.e. normally all blood is contained in blood vessels), explain why animals can get by with having arterioles and veins innervated by the sympathetic nervous system without antagonistic innervation by the parasympathetic nervous system.

Sympathetic Stimulation of the Muscular Walls of Arterioles and Veins