In smooth muscle cells of blood vessels the principal effect of activation of these receptors is vasoconstriction. Blood vessels with α1-adrenergic receptors are present in the skin, the sphincters[3] of gastrointestinal system, kidney (renal artery)[4] and brain.[5] During the fight-or-flight response vasoconstriction results in decreased blood flow to these organs. This accounts for the pale appearance of the skin of an individual when frightened.