#alpha_receptor__alphareceptor__alpha-adrenergic_receptor__alpha-adrenoceptor__alphaadrenoceptor  receptors postulated to exist on nerve cell membranes of the sympathetic nervous system in order to explain the specificity of certain agents that affect only some sympathetic activities (such as vasoconstriction and relaxation of intestinal muscles and contraction of smooth muscles)
  supertype:  receptor  a cellular structure that is postulated to exist in order to mediate between a chemical agent that acts on nervous tissue and the physiological response
  part of:  sympathetic_nervous_system__sympatheticnervoussystem  originates in the thoracic regions of the spinal cord; opposes physiological effects of the parasympathetic: reduces digestive secretions; speeds the heart; contracts blood vessels
     part of:  autonomic_nervous_system__autonomicnervoussystem__ANS  the part of the nervous system of vertebrates that controls involuntary actions of the smooth muscles and heart and glands
        part of:  nervous_system__nervoussystem__systema_nervosum__systemanervosum  the sensory and control apparatus consisting of a network of nerve cells
           part of:  body__organic_structure__organicstructure__physical_structure  the entire physical structure of an organism (especially an animal or human being); "he felt as if his whole body were on fire"

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